Need advice on what to add as I slowly reduce my CYA

another one

Well-known member
Jul 1, 2010
49
Seattle area, WA
Ok, so for the past 4 weeks I've been draining water to reduce my CYA (indoor pool, and I've been listening to the pool store guys and letting them do my testing).

when I started draining my levels were (from my TF-100):

pH - 7.5
FC - 16.5
CC - 0.5
TA - 175
CH - 300
CYA - 60

I'm draining around 700 gallons per day (missed a few days), and so far I've drained 14,000 gallons, which according to my spreadsheet means the pool has 40% new water, and 60% old water.

My levels today are:

pH - 7.8
FC - 2.5
CC - 0
TA - 65
CH - 150
CYA - 35

My CH has fallen by 50%, TA by 65%, and CYA by 40%. Along the way, the only things I've added is 9 lbs of calcium chloride to get the CH up and 1 quart of 31% muriatic acid to help lower the TA.

So when I add bleach today to get the FC up to 4, should I try to adjust anything else? By my calculations, I still need to drain about 10,000 more gallons to get the CYA down to 25 which will take about 2 more weeks.

PS - pool calc says I should add 33 lbs of CaCl to bring CH up to 250, real question is should this be done now or in two weeks.
 

duraleigh

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In The Industry
Apr 1, 2007
31,682
Sebring, Florida
The pH could be lowered if you like. It's in the normal range but the top end of normal. Other than that, everything looks fine. How does your water look?
 

another one

Well-known member
Jul 1, 2010
49
Seattle area, WA
Water is perfect, my wife commented last night on how there was no chlorine smell whatsoever.

I think the pH is up because we've been using the spa, the well water pH is around 7.5.
 

another one

Well-known member
Jul 1, 2010
49
Seattle area, WA
Last question:

I plugged in the desired pH level into the pool calc and with FC 4, pH 7.5, TA 60, CH 150 and CYA 35, the CSI is -0.46 which says "Potential to become corrosive to plaster". Do I have to correct this by raising CH?
 

Bama Rambler

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TFP Expert
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Jun 22, 2009
23,036
SouthWest Alabama
In a plaster pool your CH needs to be higher anyway so that's the correct thing to adjust. I'd bring it up to the recommended range listed in the Pool Calc.
 

another one

Well-known member
Jul 1, 2010
49
Seattle area, WA
Thanks, I'll bring it up to 200+. I'm trying not to add too much that I'm going to drain away anyway over the next 2 weeks, but now that we have a working heater, and it's going to be 90 degrees for the next 4 days, we'll be using the pool a lot. :-D
 

Melt In The Sun

TFP Expert
LifeTime Supporter
Oct 29, 2009
3,899
Tucson, AZ
Are you done replacing water? I would wait to add the calcium til you are. I don't think -.46 isn't low enough to cause damage over that short amount of time.
 

Isaac-1

TFP Expert
LifeTime Supporter
May 10, 2010
6,711
SW Louisiana
What CYA level are you shooting for? I maintain my indoor pool at a CYA level of 20 ppm, just because the advice around here is some CYA is good, and the common test only read down to 20ppm.

Ike
 

another one

Well-known member
Jul 1, 2010
49
Seattle area, WA
I'm shooting for a CYA of 25 for now, this winter, if we stop using the pool for a while, I'll drain some more water and try to get it down to 20 which seems to be the recommended level.
 

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