Newbie with high CH

rwhaight1

Member
Jul 4, 2007
7
Our pool is about 1 yr old, this is our first winter. We live in Florida and kept it open, no heater. In ground Gunite 10,000 gallons with cartridge filter. Current temp is 67. We use the BBB method all summer, but went back to using 3" pucks with stabilizer for winter because it's easier and we don't swim in winter months. Test once a week in winter and usually only have to add muriatic acid. The problem is that the CH keeps going up. Is this because of the puck or does it have something to do with the water temp or some other reason. Water is always clear.

numbers
FC= 3.5
CC= 0
PH= 7.8
TA= 90
CH= 440
CYA= 60

Any help or suggestions would be appreciated.

Thanks
 

chem geek

TFP Expert
LifeTime Supporter
Mar 28, 2007
12,083
San Rafael, CA USA
Neither BBB (that is, bleach or chlorinating liquid) nor Trichlor pucks will add to CH. The latter adds to Cyanuric Acid (CYA), but neither adds to Calcium Hardness (CH).

A new pool will have a strong rise in pH and will rise in CH due to the curing of plaster. Usually, this is most extreme in the first few months and subsides a lot by the time you get to the one year mark where you are at now. There may still be some slow curing going on (I believe some report it up to 2 years), but it should be rather slow.

If pH rise were solely from the curing of plaster, then in your 10,000 gallon pool for every 10 ppm rise in CH this would require about 3 cups of Muriatic Acid (31.45% hydrochloric acid). So if you figure how much acid you've added and if that is greater than or equal to the corresponding CH rise, then that would explain what you are seeing (the extra acid being that to counter carbon dioxide outgassing).

Other than plaster curing or explicit addition of calcium chloride or Cal-Hypo, the only other way CH increases is through evaporation of the pool water with refill from water that has CH since whatever is in the fill water is incremental and added to the pool when there is evaporation. Unlike evaporation, splash-out and refill will only increase CH if the CH level of the fill water is higher than that of the pool water. You can test your fill water to see it's CH level.

Richard
 

rwhaight1

Member
Jul 4, 2007
7
Thanks for the info, going back through my records, I see that the CH jumped after I put cal-hypo, and has steadily kept going up. I will drain some water and add new after I test my fill water 1st.

Thanks Again
 

salinda

LifeTime Supporter
Feb 25, 2008
130
Los Gatos, CA
rwhaight,

You might want some "more expert" advice than mine, but I have gotten all of the expert advice before. Who told you your CH is high at 440? The pool store told me my CH was high 3 years ago, but the folks at PoolForum and here at TFP kept my panic at bay and they were right.

Mine is 530 and I just did a 30% drain and refill! My fill water is somewhat hard and I knew I couldn't get it down much with the drain and refill, but I now believe that it was well over 600 before the drain and it was balanced according to PoolCalculator and the water was crystal clear and no scaling for years. I only did the drain and refill because I felt it was "time." If you use PoolCalculator diligently and do things like watch your ph (don't let it go to high) and keep your TA low, you will be fine with your pool water at 440 CH

I edited this because I punched in your numbers and your water is perfectly balanced with your numbers. Good job!
 

chem geek

TFP Expert
LifeTime Supporter
Mar 28, 2007
12,083
San Rafael, CA USA
Ditto about the higher CH not being a problem. Most pool users do not see scaling until the saturation index gets to around +0.7 and others don't see it until it gets to around +1.0. So you've got leeway and can always compensate somewhat by lowering the TA which will also help reduce the rate of pH rise from carbon dioxide outgassing and you can eventually lower the pH closer to 7.5, but don't sweat it now. The Pool Calculator gives a saturation index for your numbers of +0.24 so only a little high so don't worry about it.

Just note that as the temperature rises, the saturation index will rise, but you can just lower the pH (if needed) when that happens.

Richard
 

rwhaight1

Member
Jul 4, 2007
7
Thanks for all the advice. We emptied some water out of the pool and refilled with new. CH looks good now, down to 280.

Thanks Again