CYA very high with unknown reason

jbone1313

Member
Mar 26, 2021
17
Arizona
Last year, we had to drain and refill our pool.

After refilling, I went to the pool store and had the water tested. They gave me CYA and had me add the whole bottle, and they told me to come back in a week or so and have the water retested. After the second test, they gave me more CYA, and I added it according to their instructions.

A couple weeks ago, we treated the pool with ascorbic acid. After my testing kept showing low PH, I went to the store to have it professionally tested to make sure I checked everything accurately.

The test showed a level of CYA at 130ppm! My test here at home confirmed that.

Questions:

1. How could this have happened?
2. Is it possible they messed up the test last year? It seems really hard to mess up.
3. Is it possible the ascorbic acid could be throwing off this test?

I would hate to drain the pool unnecessarily.

Any other thoughts or advice would be appreciated.

Thanks!
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
44,310
Laughlin, NV
Pool Size
6000
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
How much stabilizer have you added, a 'bottle' is a measurement that is hard to calculate from.
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
44,310
Laughlin, NV
Pool Size
6000
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
Well. What has happened happened. Use your current test results and drain the pool to lower your CYA.
 
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mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
44,310
Laughlin, NV
Pool Size
6000
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
That’s the plan. I figured I would ask here first. Thanks for your thoughts.
And quit using the Trichlor for your every day chlorine needs. They are 40% CYA.
 
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mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
44,310
Laughlin, NV
Pool Size
6000
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
You have two choices, liquid chlorine or a Salt Water Chlorine Generator. With liquid chlorine, you add what the pool needs EVERY DAY. Or with the SWCG, it creates and adds the chlorine for you every day.
 
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CrystalRiver

Well-known member
Jun 19, 2020
648
Massachusetts
Trichlor pucks are adding CYA at a rate of approximately 2 ppm per day (based on daily FC loss to UV of 2-3, and the ratio of FC to CYA in pucks). That means you raise the CYA by about 60 ppm per month, or 360 over the course of six months. These are rough numbers but you get the idea - since CYA doesn't leave the water, it rises very quickly.

I use liquid chlorine. It takes but a couple minutes to do each day. Others prefer SWG, which take even less time, but cost a lot more up front.
 

setsailsoon

Gold Supporter
LifeTime Supporter
TFP Guide
Oct 25, 2015
4,277
Palm City/FL
Pool Size
12800
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Also, as your CYA level increases you need more FC for adequate disinfection. Suggest you read through this document ABCs of Pool Water Chemistry. Ask any questions you may have and you'll be a TFPer in no time!

Chris
 

jbone1313

Member
Mar 26, 2021
17
Arizona
Sorry to bump this thread, but I wanted to express my appreciation for all the help. I am now a Bleach Believer. Screw the pucks. I read through all the Pool School stuff, and it has helped tighten up a lot of knowledge gaps. What a great forum. :)

Thanks!
 

march2012

LifeTime Supporter
Jan 21, 2012
472
TX
Sorry to bump this thread, but I wanted to express my appreciation for all the help. I am now a Bleach Believer. Screw the pucks. I read through all the Pool School stuff, and it has helped tighten up a lot of knowledge gaps. What a great forum. :)

Thanks!
you can auto add bleach with a stenner pump. I have this one with a built in timer. Stenner Econ T Automatic Dosing Peristaltic Metering Pump E10T2B 120V NSF 50: Amazon.com: Industrial & Scientific

It can do 8.5 gallons per day or .35 gallons per hour.

I use a 55 gallon drum that I bought for $25 off craigslist.

The checkvalve screws into the top 1/2" NPT of the puck dispenser. That 1/2" npt I believe is for a pressure gauge. You might need an extender so the check valve doesnt protrude into the puck tube so you can still put pucks in.
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
44,310
Laughlin, NV
Pool Size
6000
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
You might need an extender so the check valve doesnt protrude into the puck tube so you can still put pucks in.
That is very dangerous. If you put pucks in and then liquid chlorine, an explosion is likely to occur. NEVER mix different forms of chlorine.
 
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mgtfp

Bronze Supporter
Mar 5, 2020
1,026
Melbourne, Australia
Pool Size
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Astral VX 7T
That is very dangerous. If you put pucks in and then liquid chlorine, an explosion is likely to occur. NEVER mix different forms of chlorine.

Wonder whether that's what triggered James to start this thread:

 
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