CH continues to rise...

[ITR]

Hey there...some of you might remember the pool was a new construction and filled the week before Christmas this year...so just under six months...(and completely drained and refilled once due to a calcium scale build-up due to the PB not doing an acid wash on the new Stonescape application. I have a question...

My CH was stable for a few months (in the 425 nieghborhood). The last few weeks it has been rising. Last Sunday it was 475. CH is now at 500 although CSI is at -0.03. The only thing I have added over the last few weeks is HCL, Bleach, Boric Acid (from Duda), and one 40lbs of solar salt.

Question: Do you think this is happening due to the curing process or for some other reason?

 

[BoDarville]

It may be happening as a by-product of topping it off with fill water. Although water evaporates, calcium does not. If your fill water has a higher CH level than the water in the pool, your CH will gradually rise. It's probably worth your time to test your fill water's CH.

 

[ITR]

Good point that I failed to mention. No fill water has been added we get plenty of rain here in Central Florida. Only rain has been added in addition to the Boric Acid and solar salt.

 

[duraleigh]

After 6 months, I would assume your plaster would not throw off any calcium. That said, I can think of absolutely no other explanation.

 

[ITR]

I must have had a bad test...it was at 475 today. Thanks for your help.

 

[LisaDLu]

It may be happening as a by-product of topping it off with fill water. Although water evaporates, calcium does not. If your fill water has a higher CH level than the water in the pool, your CH will gradually rise. It's probably worth your time to test your fill water's CH.

BoDarville - I'm having rising CH too. My fill water is 100 and my CH for today was 450. You say if the fill water has a higher CH level than the water inside the pool, then CH will gradually rise. Does that mean with my numbers my rising CH is probably not due to the fill water? We replastered in January so maybe it is still just the calcium from the curing plaster? I was considering a water softener for my pool but I'm not sure. Sorry that I'm hijacking this thread.

 

[bdavis466]

That is not correct. Every gallon that evaporates leaves its calcium behind. Every gallon you replace adds an additional calcium to the pool which will cause the CH to slowly rise. If you drain water from the pool and replace it with fill water, then your CH will drop.

You have a lot of evaporation and your CH rise is more than likely from the fill water.

 

[Richard320]

BoDarville - I'm having rising CH too. My fill water is 100 and my CH for today was 450. You say if the fill water has a higher CH level than the water inside the pool, then CH will gradually rise. Does that mean with my numbers my rising CH is probably not due to the fill water? We replastered in January so maybe it is still just the calcium from the curing plaster? I was considering a water softener for my pool but I'm not sure. Sorry that I'm hijacking this thread.

The CH stays.

Let's say for easy math that your pool is 50" deep and your CH is at 450. You lose 2" to evaporation. That's 4%, .04. Same CH in .96 as much water, so CH will read 450/.96 = 469 CH. If you refilled it with distilled water, it would go back down to 450. But you aren't. You're using water at 100 CH.

So... (.96*469) + (.04*100) = 454

You just need to know your average depth and you can figure out how much CH you add with every inch of refill water.