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Water Chemistry Log

Water Chemistry Log

The pool is finally done and now I have the unenviable task of getting all the water chemistry in balance.  I must thank Ben Powell and all the members up at the Pool Forum website for all the knowledge they have imparted to me concerning pool water chemistry.  From everything I've read up until now, here is what I would consider balanced water.  This is the goal I'm shooting for:




There is a ton of stuff to know about pool water chemistry and I can't get into all the details.  Here is a capsule summary of each of the measurements.

  • FC (Free Chlorine) - Chlorine that is not bound to any compound and is available to sanitize.  It needs to be above 1.0 always (for concrete pools) and my optimum range is 2.0-2.5 to be effective as a sanitizer.  Shocking levels are around 5.0.  6% or 10% Sodium Hypochlorite (common household bleach) is the best agent to increase FC levels.

  • CC (Combined Chlorine) - Chlorine that IS bound and is no longer useable as a sanitizer.  Any value other than zero means that you have bound chlorine that is useless.  Keeping FC above 2.0 at all times is the best method of keeping this value at zero.  Shocking is an alternative way to make CC go to zero.

  • TC (Total Chlorine) - The sum total of the Free and Combined Chlorine.

  • PH - Tests how acidic/basic the water is.  Too low (< 7.0) and the water becomes corrosive causing plaster erosion and burning eyes.  Too high (>8.0) and chlorine cannot do its job properly, causing the potential for algae problems to increase.  Also, as PH rises, the potential for scaling problems also increase.  For concrete pools, PH will tend to continually rise for the first 3-4 months after finishing the pool.  This has to do with the concrete curing in the water.  Muriatic Acid is used to lower PH.  Aggressively adding acid to the pool for the first few months will be the order of the day.  The ideal range for PH is around 7.4 - 7.8.

  • TA (Total Alkalinity) - Different from the alkalinity in PH.  Serves as a buffering agent to prevent PH from swinging wildly.  Too much alkalinity (>120) causes scaling problems.  Too little (<60), and it will be difficult to keep PH stable.  The ideal range is somewhere around 80-120.  Sodium Bicarbonate (e.g. Arm and Hammer Baking Soda) is used to increase TA.  To lower TA, the PH of the pool needs to be lowered to around 7.0-7.2 then heavy aeration applied.

  • CA (Calcium) - Measures the amount of dissolved calcium in the water.  Too much CA (>300ppm) and scaling problems will be prevalent.  Too little (<100ppm), and the water becomes starved for calcium and will take it from the pool surface, causing plaster erosion/etching on the pool's interior.  In AZ, hard water is very typical.  Also, if the pool has a concrete interior (Marcite plaster/Pebble-Tec), CA will steadily rise during the first year due to calcium coming off the walls of the pool.  The best way to effectively reduce CA levels is dilution (draining/refilling).  I happen to have a water softener, and I plan to refill using soft water to keep the CA levels low.

  • CYA (Cyanuric Acid or "Stabilizer") - Protects chlorine from being destroyed by UV light.  CYA puts chlorine into reserve.  Too little CYA will require constant addition of chlorine to the pool to compensate for the dissipation.  Too much will reduce the effectiveness of chlorine as a sanitizer, which then requires running chlorine at higher levels in order to compensate.  Like CA, there is no way to reduce CYA except for dilution.  Increasing CYA can be done with pure stabilizer in powder/granular form or using "Stabilized Chlorine."  The most common form is Tri-Chlor or Di-Chlor tablets.

  • SI (Saturation Index) - The Saturation Index is a broad indication of how likely a pool and heater will tend to scale.  On the high end, the tendency to scale increases as the SI gets above 0.5.  On the other end, the tendency for the water to be corrosive - begin to damage concrete-based pool surfaces - increases as the SI value gets below -0.5.  A good range to keep it in is between -0.2 - +0.2.  SI is dependant mainly on PH, TA, CA, and water temperature.  The SI value is calculated as a range from an excellent calculator written by Ben Powell from Pool Solutions

This page is going to log my journey from getting from square one to balanced water.  Balanced water should be sparkling clear, clean, and safe.  Here again are the numbers that I got from the initial testing of my hard water and soft water supply:


I should add that I did not measure the chemistry of the water right after fill.  I didn't get a chance to test it before the startup man came and added a bunch of chemicals to it.  However, I watched carefully as he added the initial chemicals and this is what he added on Wednesday, February 5, 2003 around mid-morning:

  • 3 - 3" Trichlor tablets (stabilized chlorine)
  • 2 gallons of 10% Sodium Hypochlorite
  • 1/2 gallon Muriatic Acid
  • 7 lbs of granular Stabilizer
  • A quart of Scale and Metal remover


The pool is right at about 13,000 gallons and the spa is at at 800 gallons for a total of 13,800 gallons.  All the chemicals I will be adding from here on out will be based on that number.  What that said, lets get to the testing:

Friday, February 7, 2003 - AM
This is my first reading of pool water using Pool Solutions PS-233 test kit.  I tested the water on Friday morning:


Other than the chlorine reading, the rest of the numbers are not all that bad.  I was quite surprised.  The chlorine that was added on the day of startup skyrocketed the chlorine levels up to 13.0ppm.  This is high but it will be coming down on its own in a few days.  The Muriatic Acid that was added brought down the PH from the fill level of  7.6 down to 7.3.  The Total Alkalinity (TA) number is a little lower than the original value tested from the tap water supply.  The Calcium levels are right where I expect them to be: HIGH.  This will come down later as I continue to change water out of the pool through backwashing and partial drainage and refill using the soft water supply.  Actually the pool startup guy said that for AZ, the stabilizer (CYA) levels should be closer to 80 - 100.  That doesn't sound right.  A lot of what I read from the Pool Forum states much lower CYA levels (10-30ppm) are sufficient.   I think I'm going to do a little experiment this spring.  I'm going to keep the CYA at a minimum and see how fast the chlorine gets eaten up.  If I see that it dissipates too quickly, I'll slowly bring CYA up slowly to see what kind of effect it has on chlorine retention.

Chemicals Added:  none

Wednesday, February 12, 2003 - Early PM
A look into the skimmer has shown that all 3 3" Tri-Chlor tablets have dissolved by now.  A little less than a week has passed before taking the 2nd reading, and here are the results:


The chlorine reading has come way down and the stabilizer (CYA) levels have gone up slightly to 45.  Eventually, I want to be running the chlorine at about 3 and the stabilizer levels at 20-30.  I'll have to do a partial drain of the pool to get rid of CYA.  The chlorine levels are still at what I consider 'shock' levels.  A few more days and they should be coming down closer to where I want them.  The pH has shot up to 8.3, so I'll be adding more Muriatic Acid.  Both the TA and CA have gone up.  No doubt the cement from the Pebble-Tec surface is adding more calcium to the water.  I still have yet to plumb the AWL to the soft water source, but when I do, after a number of backwash cycles and partial drains, this number should come down.  I'm hoping to get the CA levels down to about 200 - 250.  The Saturation Index (SI) value is now in the "high tendency" range due to the shooting up of the PH and calcium levels, but this should be quickly remedied when the acid is added and the water gets stable.

Chemicals Added:  1 quart Muriatic Acid

Thursday, February 13, 2003 - Early AM
Sure enough, the PH has come down quite a bit.  Its gone from 8.3 to 7.4 overnight.  I didn't test any of the other indicators today.  I just wanted to find out how fast Muriatic Acid works in bringing down PH.  The answer is, "pretty fast."  Incidentally, I had the filter running all night to make sure the water was turning over.


As a result of the PH coming down, the Saturation Index has come back down to acceptable levels.

Chemicals Added:  none

Saturday, February 15, 2003 - AM
We had a huge downpour Thursday and Friday and it looks like it added a couple of inches of water into the pool.  In fact the water level went from half way up the skimmer to the point where the bond beam and the deck meet.  I had to drain several hundred gallons of water from the pool in order to get the water level back down to where it needs to be.  Here is the reading from this morning:


As you can see, the PH has shot up again so more acid will be needed to bring down the PH.  It looks like the CA levels haven't been affected by the pool draining/rain refilling at all and the Free Chlorine/Total Chlorine levels are still unchanged from midweek.  A lot of this initial and frequent (every few days) testing is for my benefit to see at what rate the indicators change.  I know I'll be going through a lot of test kit chemicals early on, but the education that it will provide me will be invaluable.  With that said, I held off on doing the CYA test because I can only do a couple more before I have to order more reagent.  I'm beginning to see that when PH gets close to 8.0, that's when the SI value starts to creep into the 'unacceptable' range.

Chemicals Added:  1 quart Muriatic Acid

Saturday, February 15, 2003 - PM
I did a re-test of the PH again just to see how fast the acid works.  I tested the water at both ends of the pool and also in the spa to make sure the acid was evenly distributed by making sure the measurements were consistent:


As you can see, the acid works extremely quick.  About 4 hours had passed from the time I added the acid to when I tested.  Now that the PH is down, I turned on the aerator, waterfall, and spa dam wall spillway to create some aeration action.  While the TA is actually at an acceptable level, I'd like to see if this course of action will bring down the value somewhat.  I'd like to get the TA to about 100 although its not absolutely crucial.  Its interesting to see what a PH swing of 1.0 will do to the SI value.  It went from +0.4/+0.8 to -0.6/-0.2, which is starting into the unacceptable range but on the opposite end of the scale.

Chemicals Added:  none

Sunday, February 16, 2003 - AM
I wanted to see how the TA value is affected after a whole night of heavy aeration.  I did the test around 10:30 in the morning (just for PH and TA) and here are the results:


I was slightly shocked to see the PH rise up again so quickly.  From what I've read on the Pool Forum site, a TA value of 120 is already on the high end of the "optimum range."  I'm trying to bring it down slightly more toward the center of this "optimum range," and it does look like the heavy night of aeration has had some effect.  The TA is now 110 which is slightly down from yesterday's test value.  However, with my PH swinging so wildly, I'm not sure I want to bring it down any more.  In fact, with that type of PH variation in just the last day, I'm guessing I really need to bump it up a notch.

Notice that the SI value has come back to the optimum level.  The one thing I've really learned by punching my PH, TA, Temp, and CA numbers into the SI Calculator at the Pool Solutions website is that I'm really getting familiar with what values my PH, TA, Temp, and CA should be in order to minimize damage/corrosion to the pool surface and pool heater.  Right now, with the water temperature being so cold (61F), its gives me some latitude having the other parameters not be at their optimum levels (e.g. TA=120, PH=7.4, CH=370) and still be in a good SI range.  However, when summer rolls in and the pool water rises to 85F, the other parameters are going to have to be more optimum in order to keep in that same optimum SI range.  Roughly speaking, when the temperature hits 85F, I will be shooting to get TA=120, PH=7.4, CH=250.  This would keep my SI at -0.1 to 0.2.  Like I mentioned earlier, the CH will be my biggest challenge.

Chemicals Added:  none

Sunday, February 16, 2003 - PM
As if I don't have enough to keep track of, I added yet another parameter to the mix tonight: salt for the Clearwater salt water chlorinator.  I ran over to the local Leslie's Pool supply store to pick up a bottle of salt water test strips.  I didn't realize they are so expensive.  The bottle was $11 and I figured there were 50 or so strips in there.  To my dismay, I found only 10 strips - $1 a test.  I started looking on the Internet to find a digital salt water tester and I found several good ones.  I'll probably ask the fine folks on the pool forum to see what they might recommend.  Anyways, I did an initial test of the pool water prior to dumping in the salt this evening.  I got a reading of around 1750ppm.  According to the manual from the Clearwater Salt Water Chlorinator, I need to get the salt levels up to 4000ppm before I can turn the unit on.  They had a handy little chart in the back which basically said I needed to dump in 250lbs of salt - five 50lb bags.  It wasn't too bad.  I purchased 9 bags of Morton's White Crystal Salt at Home Depot for $2.94 for a 50lb bag (I bought 9 bags instead of 5 when I mistakenly thought I needed to go from 0ppm to 4000ppm.  I didn't realize that I was starting from a level of 1750ppm).  Its the same kind of salt they use for water softeners.  The startup guy recommended that I get the finer salt rather than the bigger pellets.  This is no doubt to help the dissolving process to go faster.  I did my best to spread it evenly around the perimeter of the pool, then brushed it around the bottom until it all dissolved.  It took about 30 minutes to do.  I'll let it get uniformly distributed throughout the pool/spa by leaving the filtration pump on all night and I'll do another salt level test in the morning.

Monday, February 17, 2003 - AM
I wanted to run the full gamut of tests this morning to see what kind of effect, if any, the added salt would have on the pool chemistry.  Here are all the readings:


The salt level has jumped from 1750ppm right to 4000ppm - right at the level it needs to be at per the manufacturers instruction.  I guess the "how-much-salt-to-add" chart in the manual is pretty accurate.  Kudos to them.  The first surprise I got was the Chlorine levels.  It shot up to 9.5.  I don't really understand this.  We used the spa for the first time yesterday and if anything, I thought the FC levels might even come down from the previous level of 6.0.  I'm guessing that salt, having a chloride component to it, must have added to the chlorine levels.  However, I was under the impression that an electric current must pass through the cell plates in order for the conversion of salt to chlorine to take place.  And I know the unit hasn't been turned on yet.  And even if it was, the FC prior to this was up at 6, so I don't know why it would have made more chlorine.  For sure, I know I haven't added any chemicals in the last day.  Well, if anyone can explain this phenomenon to me, I'd love to hear an explanation.  Please email me if you care to fill me in on what happened.

The PH is again on the rise.  It looks like I'm going to have to be aggressive with adding acid until things stabilize.  I don't know how much the new Pebble-Tec surface curing is adding to the PH issues.  All the other indicators - TA, CA, and CYA levels have all been stable for about a week now.  We'll see how long they will continue to do so.  The high PH has pushed the SI value back to the not-so-good levels.

Chemicals Added:  1 quart Muriatic Acid

Saturday, February 22, 2003 - AM
I did another full battery of tests minus the CYA test this morning.  It looks like the chlorine is coming down finally to normal levels.  I want to be running chlorine at about 2.5 - 3.0 with CYA levels around 40-50. It looks like rising PH is going to be a characteristic of my pool.  I'll have to add another quart of muriatic acid to get it back down to acceptable levels.  It looks like the CA is still climbing.  Today, I measured it at 390 and no doubt it will continue to climb as the Pebble-Tec interior continues to cure in the water.  The high PH level is contributing to the SI value being in the unacceptable range.


Chemicals Added:  1 quart Muriatic Acid

Saturday, February 22, 2003 - PM
I just wanted to see how the PH is doing with the acid I added this morning.  Its down to an acceptable level, but I know its going to be up again in a couple of days.  I'm going to add another pint of so of muriatic acid to pre-empt the move.  A pint will move it down to about 7.0 or so based on what I've seen so far.  Notice the SI range is back within acceptable levels due to just the PH change.


Chemicals Added:  1 pint Muriatic Acid

Friday, February 28, 2003 - PM
I've been adding Muriatic Acid to the pool in small quantities all week without testing the PH.  I was hoping that by the end of the week, it would be around 7.5.  I re-tested in the late afternoon and discovered to no surprise that it was at 8.0.  I'll retest everything in the morning, but for now, I'm going to add another quart of acid


Chemicals Added:  1 quart Muriatic Acid

Saturday, March 1, 2003 - AM
I've been doing a lot more reading about CYA in the last week up at the Pool Forum and I'm becoming more and more convinced that MUCH lower CYA are necessary.  You can find the thread here.  One poster referred me to a very interesting article that had some very interesting charts.  One such chart was the "Chlorine Staying Power" which charted "% CL Remaining" against "ppm Cyanurics" According to that chart:

10ppm CYA -> 87% CL retention
20ppm CYA -> 95% CL retention
30ppm CYA -> 98% CL retention
70ppm CYA -> 100% CL retention

Its interesting that anything above 30 ppm all the way to 70ppm basically gives you effectively the same chlorine retention percentage. This is just my interpretation of the data, but it sure looks like 10ppm CYA will do a pretty darned good job at 87%. Doubling the CYA levels from 10 to 20 just gives you an additional 8% CL retention power. Going from 20 -> 30 does almost nothing. One big caveat though is that this data measures the CL levels only after an hour. I wish it measured the CL levels with multiple data points after x, x+1, ... days rather than a single hour. Its hard to do time-based extrapolation based on just an hour (one data point).  I think what I'm going to do this summer is to do a partial drain of the pool to get both CA and CYA levels down.  After going through all the information this week, I'd like to run CYA at 10ppm to start with, and have it creep up to 20 or 30 max, depending on how fast the chlorine is being dissipated.  I have a salt water chlorinator that will be able to maintain my chlorine levels regardless of how much CYA is in the pool, so theoretically, I could run with CYA=0.  In fact I have a friend who didn't even know what CYA was - 2 years into owning his pool.  When I asked him about algae problems or low chlorine problems, he said he never had either of those problems.  I found out later that he had a salt water chlorinator from the beginning that was making up for the chlorine loss.  Apparently this chlorinator unit was working full bore trying to produce enough chlorine to keep the levels up.  When I asked him about the condition of the chlorinator cell plates, he said that there was NO build up on it and that he's only cleaned the unit once in the 2 years he's had it.  That encourages me since I have the same type of salt water chlorinator as he does.  Since then, he's added CYA to his pool and he says now, he notices that the chlorinator unit doesn't run as long, which makes sense.  With all that said, I'm still a little concerned about overtaxing my chlorinator by going CYA=0.

Back to my test readings:


As expected, the PH has come down again, but not as much as it used to with a quart of acid.  There's no real change in the rest of the readings except that the TA is still coming down slightly.  This is good.  I was thinking at first that the wild PH swings was due to not having enough TA and my initial thought was to actually raise it.   However,  I've talked to a bunch of people from AZ who have told me about their similar "Wild PH" stories.  Most believe that the concrete curing in a new pool is causing the rapid PH rise and that eventually it will slow down or stop.  In the beginning, they tell me that LOTS of Muriatic Acid is required.  Eventually, I want TA to stop at 90.  Even though PH is where it needs to be, I'm going to add some more acid later this weekend to pre-empt the rise in PH that I'll know I'll see in a few days from now.

Chemicals Added:  1 quart Muriatic Acid

Saturday, March 8, 2003 - AM
This week, I added close to another half gallon of Muriatic Acid to the pool as midweek tests have indicated PH continuing to rise.  All my initial Muriatic Acid from the startup is now gone.  I purchased a couple of  2-1 gallon packs from Home Depot for $3.87 a pack.  That comes out to about $2.00 a gallon.  I'm using close to 1/2 gallon of acid a week to combat the rising PH.   Here are the results of my measurements this week:


I found it odd that the chlorine levels are rising from last weeks measurement of 4.5.  FC is now at 6 and I still haven't turned on the salt water chlorinator yet and haven't added any chlorine since the initial startup of the pool a month ago.  Or so I thought.  Just to be sure, I went over to the equipment area and lo and behold, the salt water chlorinator unit WAS on.  I don't know when I turned it on, but that would explain it.  I noticed that it was at its lowest setting.  Interesting that it would make the chlorine go up to 6 at its lowest setting.  I'm wondering if the unit can somehow can measure the CYA (which is 45) and compensate for it so that the correct levels of chlorine are produced.  I doubt it.  On another note, the TC measurement actually came in at 4.  I don't know why it would be different than the FC value,  but if it doesn't match the FC, I usually just "make" it match.  It could also just be the accuracy of the test is not that great.

Anyways, PH is right around where I want it.  The TA is continuing to drop as expected.  I'm running the PH slightly lower than 7.4 during the week (around 7.0-7.3) to pre-empt the quick PH rises with medium aeration to boot, so the TA should gradually continue to come down.  I don't really want it to drop much more than its currently at.  I'd like to keep it around 80 - 90.  The Calcium (CA) levels are on the move upward again as the concrete-based Pebble-Tec interior is continuing to add to the water as it continues to cure.  I haven't measured CYA in a while, but I'm guessing its still at 45 since I haven't added any more stabilizer since the startup.  The SI value is showing the water to be slightly corrosive due to the lower PH and TA values.

Chemicals Added:  none

Wednesday, March 12, 2003 - PM
Well, its starting to really heat up around here.  The last few days have produced some pretty strong sunny days.  Finally, after about a month or so, the chlorine levels have finally dropped to where I want to be running at.  Again, the PH is has risen back to around 8.0 so I'll be dumping in more acid.

Chemicals Added:  1 quart Muriatic Acid

Saturday, March 15, 2003 - AM
I've decided to do the partial pool drain/refill sooner rather than later.  I figured there's no real good reason to wait till the end of the summer to do it.  The CA levels will continue to rise whether they are at they're at their current levels or they are at lower levels.  The disadvantage to doing it later is that the pool suffers the consequences of having high levels of CA (scaling) through the summer until the drain occurs.  With that said, I wanted to test the water completely one last time before doing the drain this weekend.  Here are the measurements:


I finally turned on the salt water chlorinator and you can see the chlorine levels have risen a bit.  I'm not too concerned.  I'll be tweaking the output setting all summer to get it to produce a constant level of chlorine (around 2.0 - 2.5).  The only real news here is that the CA levels are still rising.  They have gone from 400 last week to 430 today, so I'm glad to be doing the pool drain this weekend.

It turned out to be kind of a pain to drain a pool.  The City of Chandler has some rigid rules for draining a pool.  A "Notice of Intent to Discharge Liquid" permit is required by the city to drain a pool, and must be procured at least 48 hours prior to draining.  Fortunately, the process of getting the permit is easy.  It can done right over the phone and its free.  Draining the pool has some restrictions.  For example,

  • All flows must be monitored to prevent any type of flooding or nuisance.

  • No chemical of any type shall be added to the pool for at least 48 hours prior to draining.

  • Only water free of dangerous chemicals can be discharged into a public right-of-way

  • Discharge of liquids will be done along curb/gutter line only.

  • Permit must be displayed in a prominent location during the draining activity.

If it weren't for all the extra bureaucracy of getting a permit, pool draining would be a snap for me. Right over my back wall is a storm drain.  I pulled out my trusted 3/4HP submersible sump pump and utility hose and tossed it over the wall and 30ft over to the street and right into the storm drain.  It took a couple of hours to drain half of the pool.


Refilling the pool turned out to be the bigger headache.  I planned on refilling the pool with soft water (CA=0) generated from our household water softener unit.  Earlier in the week, I had contacted our water softener company and learned that our softener unit takes about an hour to regenerate the softener beads.  Each regeneration produces about 800 gallons of water before another regen is necessary.  After doing the math, I calculated that with 1 hour regen times and the water necessary to refill the pool, that I could finish the refill by the end of the day.  Was I in for a rude awakening.  I discovered that the regen did not take 1 hour - that in fact, it took 3 hours to regenerate the soft water beads.  However, I also discovered that the capacity of the softener unit was actually closer to 1000 gallons and not 800 gallons like the company told me.  Nonetheless, this was nowhere near going to compensate for the fact that the regen was now going to take 3 times as long as I had anticipated.  And being that I had close to 7000 gallons of water to re-fill, what was originally planned as a day long event was going to take an additional 24 hours.


It actually worked out pretty well.  I was able to go out and run some errands during the 3 hour long regen times.  Once a regen had completed, it took me about an hour to pump out 1000 gallons of soft water into the pool (using two hoses from two soft water hose bibs in the backyard).  I had to do this for 7 cycles before I filled the pool up.  Needless to say, it was a looooonng weekend.

Sunday, March 15, 2003 - Late PM
The pool refill finished up (+/- a few hundred gallons) right around 8pm or so.  So as to make sure the water would be uniformly distributed throughout the pool, I let the filtration pump run for an hour or so.  After letting the water circulate the water for awhile, I couldn't wait to re-test the water to see how much the CA and CYA dropped.  Here are the new measurements:


As you can see, I'm absolutely thrilled about both the new CA and CYA values!  The CA value is dead-on where I would like to be ALL the time.  Unfortunately, I know that this value will continue to rise as the concrete in the pool continues to cure.  I have no idea when it will stop putting CA into the water, but I will consider doing another partial pool drain/refill in the fall if the CA levels get high enough again.  The CYA value has also come down substantially.  The new value is around 18.  This is approximate as the viewing tube in the test kit only goes to 20.  I used some extrapolation to get the final value of 18.  One unfortunate side-effect of the pool dilution is that the salt levels have also been reduced.  I need to get the salt levels to around 4000ppm, so its looking like I'm going to be adding at least 5-6 more 50lb bags of salt before I can turn on the chlorinator unit.  In the meantime, I'll just use liquid bleach.

We received a lot of rain and wind this weekend as I was doing the pool drain/refill.  As a result, a ton of leaves, general debris, and handful of small critters blew into the pool.  After seeing the new chlorine levels only at 2.0, I decided to shock the pool again to make sure everything is killed.  I added about 1/2 gallon of bleach to bring the chlorine levels up to 5-6.  Also, the PH was high again - around 8.1.  I added more Muriatic Acid to bring it down.  The water level is not quite at the halfway up the skimmer height, but I'll let it go until the morning.  Man, am I beat ... Need to get some sleep now ...

Chemicals Added:  1/2 gallon 10% Sodium Hypochlorite and 1 quart Muriatic Acid

Monday, March 16, 2003 - AM
I noticed that the water level was slightly below the midway point of the skimmer, so I added another few hundred gallons of soft water (CA=0) this morning to bring it up another 4 inches.  I re-tested all the measurements and here are the results:


The filtration pump was on all last night to clean up all the debris that blew into the pool over the weekend.  The chlorine levels are up to where I want them after adding in the sodium hypo last night.  The PH is also where I want it after adding the muriatic acid.  Surprisingly, the CA has come down quite a bit more than I would have expected it to after the additional dilution this morning.  This is actually a really good thing as I know it will continue to rise in the coming months.  The CYA has also come down more due to the dilution.  I eventually want it around 20-30, but will take my time looking at the chlorine dissipation rates.  As a result of the low PH, TA (which has come down a bit further since the test from last night), and CA, the SI range is actually in a corrosive range.  This should change relatively quickly as the PH and CA rise.  The salt concentration in the pool has also decreased due to the dilution.  According to the manufacturer's chart, I need to add an 200 lbs of additional salt to get it to the normal operating levels of 4000ppm that the salt water chlorinator requires.

Chemicals Added:  200lbs of water softener salt

Saturday, March 22, 2003 - AM
I feel I'm getting really close to where I want to be.  Almost a week has passed since I added the additional salt to the pool for the salt water chlorinator.  I turned on the salt water chlorinator unit on Monday night after adding the salt.  I noticed that the "Add Salt" LED indicator was off, so I knew I had enough salt in the pool.  Here are the new measurements:


The chlorine is a little lower than where I want to be.  I bumped up the current setting on the salt water chlorinator and hopefully, that will kick up the chlorine output.  I want to be right around 2.0 - 2.5.    The TA has slowly gone down on its own over the last few weeks and now its lower than where I want to be.  I need to keep TA >=60 or else the water becomes corrosive (metal parts in pump and pool interior start to get affected).  I need to add some Baking Soda to bring it up a tad.  I think 2 lbs will bring up TA by 20ppm for every 10K gallons of water.  Instead of pouring it in powder form directly into the skimmer and risk clogging it up, I decided to dissolve it in a bucket of hot water then pour it into the skimmer.  The CA has risen up from last weeks reading of 180 to 220 this week.  At this rate, it will be back up to 300-400 in a month or so.  That would be pretty disheartening.  I did a little chlorine test this week where I measured TC early in the morning, then again in the evening after a long, hot, sunny day.  During the day, the filtration pump was off (and thus the salt water chlorinator as well).  The TC was 2.0 in the AM and 1.5 in the late PM.  With CYA=15, the chlorine only dropped off 0.5ppm after a very sunny Arizona day.  I'll do more testing, but it seems like having such a low CYA value is still sufficient for protecting most of the chlorine.

Chemicals Added:  1 pint of Muriatic Acid in AM and 4lbs of dissolved Arm & Hammer Baking Soda in PM

Saturday, March 29, 2003 - AM
A lot has happened this week.  I backwashed a couple of hundred of gallons of water from the sand filter.  The auto-water leveler has not been hooked up to the soft water source, so I used the soft water hose bib and re-filled the pool manually with the hose.  As a result, the CYA levels are going to come down from the current level of 15.  I didn't really want the CYA level to go much lower than that, so I put in half of a 3" Tri-Chlor tablet at midweek (as of this morning, half of it remained undissolved in the skimmer so I'll wait till next week to re-test CYA).  I don't have any granular stabilizer left, and since I still half half a jug of the 3" Tri-Chlor tablets (chlorine + stabilizer), I figured I may as well use that up first before buying the pure CYA stuff.  We also had a storm front move in this week.  There was no rain, but it was windy like crazy and it dumped a whole bunch of leaves and organic matter into the pool.  I bumped up the chlorinator unit output for a few days.  I've also added about 1-2 quarts of muriatic acid slowly over the week (a little every other day or so) to handle the rising PH.  Here are the new measurements.


The biggest change is the TA.  After adding 4lbs of Arm and Hammer Baking Soda last week, the TA jumped up from 70 to 100.  This is exactly where I want TA to be.  The CA levels remained unchanged from last week at 220.  I think the backwashing/refilling with soft water made this so.  I'm guessing that CA would be closer to 240-250 this week had that not happened.  Chlorine levels are a little higher due to the higher output from the chlorinator.  PH was riding around 7.8 - 8.0 most of the week and had to be brought down with more acid.

Chemicals Added:  half of a 3" tablet of Tri-Chlor (stabilized chlorine)

Saturday, April 5, 2003 - AM
At this point, I'm just doing a lot of fine tuning.  All my indicators are about where they need to be and its really just a lot of maintaining and tweaking.  Last night, I did a PH test and the reading came in over 8.2.  I dumped in about a pint of muriatic acid to attempt to bring it down to 7.6 - 7.8.  The FC test I also did revealed that the current level at the end of the day was close to 0.5.  This is not good.  As the summer approaches, I suspect that having the CYA level at 15 is not going to be adequate to keep the chlorine that is being produced at night (during the normal filtration cycle) above the minimum levels (>1.0) during the day when the intense Arizona sun works to deplete it.  As a result, I need to get the CYA up a bit.  Also, I bumped up the output of the salt water chlorinator another notch so that it produces more chlorine and here are the readings as of this morning:


As you can see, the PH didn't respond to the extra acid I added. Its still high.  As a result, I put in another quart of acid to shock and awe it into compliance.  The half a 3" Tri-Chlor tab I added a couple of weeks ago has completely dissolved by now and it did bump up the CYA levels from 15 to around 19.  Everything else is pretty much in check.  The SI reading is a little on the high side but its just due to the high PH.  That should be coming down back to the -0.2 - 0.2 levels once PH is back down to 7.6 - 7.8.

Chemicals Added:  1 quart of Muriatic Acid

Saturday, April 12, 2003 - AM
I backwashed the sand filter last weekend so a few hundred gallons of water was replaced with soft water.  I'm backwashing about every other week now.  My thinking is that this doesn't affect the indicators that much, but still, I'm curious to see how some of the indicators will measure this week - particularly the CA and CYA.  During the week, I've added about half a gallon of muriatic acid to keep the PH down.  Here are the measurements:


Everything is in check as I expected it to be.  The CA has risen slightly to 230 even after backwashing and refilling with soft water (CA=0).  This tells me that the pool surface is still releasing CA into the water.  However, I'm surprised at how much slower the rate of the CA climb is now compared to a month ago.  Hopefully, the CA releasing action will slow even more as we head into the summer months.  I'm sure that the backwashing/refill with soft water is also having an affect on the CA readings.  The CYA actually came in lower this week than last week.  I don't know how much this has to do with the tolerance on the CYA test method and how much of it was due to the backwashing.  As I continue to test chlorine levels in the morning and at night (of the same day), I'm seeing that the FC levels reach 2.5-3.0 in the morning after the salt water chlorinator has had all night to regenerate the FC levels.  In the evening, after a full day of AZ sun, the FC levels drop to about 1.5.  This is what I want to keep it at.  I'm very happy with this cycle, and want to just maintain it at this point.  I have the salt water chlorinator output set to 2 LEDs (2 out of 10 or so), so its pretty low.  I want to raise CYA to 20 and just hold it there, so I'm adding in another full 3" Tri-Chlor tablet today.

Chemicals Added:  One 3" tablet of Tri-Chlor (stabilized chlorine)

Sunday, April 20, 2003 - AM
The extra Tri-Chlor tablet has given me the incremental increase of CYA to where I want it.  Its now sitting right around 20.  Everything else has pretty much stabilized to about where I would like it.  I left the filtration pump on during the day yesterday and as a result, the extra chlorine generation cycle produced more chlorine than I need.  Its sitting around 4.0 right now.  The FC levels fluctuate between 2.0 to 4.0 almost on a daily basis, so I'm not too concerned.  I also had a chance to check the salt levels and they are still where they need to be - right around 4000ppm.  As a result of the combination of the PH, TA, and CA, the Saturation Index (SI) is in the optimum range hovering right around zero.


At this point, I'm calling the water "balanced" and will be trying to maintain this throughout the swimming season in the summer and on through the fall.  I will continue to keep my eye on the rising CA levels and will look for an opportune time to reduce the CA to around 150 with another partial pool drain/refill (with soft water) - perhaps in the fall or next spring.

Thanks for sticking around on my quest for balanced water.  With all that work that I put in during the last 8 months, I'm thinking its a good time to start using the pool for the change.


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