Stabilizer Level Increases Significantly While Adding Only a Small Amount of CYA????

[BikerBill]

Eight year old 22,500 gallon pebble finish gunite pool in Massachusetts with DE filter and heat pump. On 6/12/2016 the stabilizer level was 51 ppm. On 8/15/2016 it was 70 ppm. And on 8/29/2016 it measured 84 ppm. The first and last tests were performed by the same pool place; the middle result was done by a different pool place. During that time, I added just six 3-inch trichlor pucks when I was away for 8 days. The rest of the chlorine came from 8% sodium hypochlorite bleach.

So how can my cyanuric acid level rise so much when I've hardly added any stabilizer? I would expect the CYA level to rise maybe 7 or 8 ppm based on the CYA content of the pucks. I have stayed away from trichlor because I wanted to keep the cyanuric acid level relatively low. The only other chemicals I add are muriatic acid and sodium bicarbonate. Can these test results be accurate? What is going on here?

Please ignore the pool information immediately below--it somehow gets attached to my posts.

 

[Mr Bruce]

I think you have discovered why pool store testing is terrible first hand.

There is a link to test kits in my signature!

 

[pabeader]

Your results are exactly why we don't recommend pool $tore testing. You can take the same sample to the same store three times in a row and you'll get four different answers.

You really need to get your own kit. Either a TF-100 or a K-2006C

 

[JoyfulNoise]

Buy a high quality test kit like the ones we recommend here (you can get any of them on Amazon from a variety of different vendors not associated at all with this site) and you'll never have to ask the question you just posted ever again.

The answer to your question is - we don't know either...pool store testing is so inaccurate that we have no idea what your CYA level is. Could be the first number, 51ppm or the last number, 84ppm. No way to know.

 

[BikerBill]

OK, so I own a K-2006 test kit. I remember doing the CYA test a number of years ago and thought it was pretty hokey. I thought the "disappearing dot" aspect was too subjective. Plus, the numbers for CYA are very difficult to read; clear plastic numbers on a clear plastic background, on an inside corner of the test fixture--bad design.

Since it doesn't seem there is anything better out there I thought I'd give it another try. I had to wash the inside of the tube directly over the black dot. I ran the test a few times (dumping out some of the mixture and adding back more) and got readings in the 45 to 50 ppm range. I'm reasonably confident in those results, so I guess I'll go with them! Thanks.

 

[pooldv]

This view tube is much better. TFTestkits.net CYA view tube

When in doubt pour the sample back and forth as many times as you want and walk around to different light. Also, always round up. An extra couple of ppm won't hurt a thing and aiming low leaves little room for error. Remember, it is safe to swim above minimum and up to shock level for your CYA, [FC/CYA][/FC/CYA]. There is a lot more room between target and shock level then there is between minimum and target.

 

[JoeSelf]

And the CYA test is done outdoors with the sun at your back.