High CYA - Should We Drain?

[neil.paradise]

Good evening - hi everyone! This is our first season with a 20,000 gallon vinyl pool in New England. Luckily we opened it to clear water. We have a CYA of 70 so we've been targetting really high chlorine levels of at least 8. This has meant pouring a gallon of chlorine in every day or two in this first week since opening. We are also hopefully converting to a saltwater generator in the next 1-2 weeks.

Question - should we drain and refill some of our water with fresh water to lower the CYA so we can use less chlorine? And/or would that be helpful to do prior to converting to saltwater?

Thanks in advance!

 

[Flying Tivo]

What test kit do you have? Can you post a full set of results from you testing?
Some links to get you started.
Pool Care Basics
FC/CYA Levels
Test Kits Compared

 

[neil.paradise]

TF-Pro test kit. We have an inground pool also.

PH: 7.5
FC: 6.5
CC: 0.5
TA: 50
CYA: 70

Thanks! The intro materials are helpful also as we learn and get our feet under us.

 

[ajw22]

If you are getting a SWG in a few weeks then leave your CYA as is. CYA 70 is perfect for a SWG.

In addition, lowering your CYA will not have you using less liquid chlorine. In fact it may have you adding more. With less CYA your daily FC loss from the sun will be higher.

Your pool will lose 2-4 ppm of FC per day regardless of CYA level. And the lower the CYA the more you will lose.

 

[Jimrahbe]

Neil,

In theory, you will not reduce your chlorine demand by lowering your CYA.. The only increase in chlorine is when you have to initially get it up to your initial FC target range.. After that, all you should have to do is replace what the pool uses each day...

If you are adding a gallon of 10% Liquid Chlorine every two days, that is about 2.5 ppm a day, so sounds about right to me..

A CYA of 70, or 60 in your location, would be perfect for a SWCG.

I suggest that you run an Overnight Chlorine Loss Test (OCLT), just to confirm that you do not have algae, even if you can't see it yet.

Overnight Chlorine Loss Test

Thanks,

Jim R.

 

[neil.paradise]

Thanks so much for the insight! Sounds like we didn't fully understand the CYA/chlorine relationship, but are not in a bad place at the moment.