CYA Question....

[court475]

I am about to test our tap water (pool is being installed tomorrow) to see how we need to start off. My question is this, might the tap water have any CYA, or does tap never contain CYA? The test uses 1/3 of the regeant that I have and don't want to do it if it's not necessary. I hope that's not a stupid question!

Thanks,
Courtney
24' x 52" A.G. in S. LA

[chem geek]

I am about to test our tap water (pool is being installed tomorrow) to see how we need to start off. My question is this, might the tap water have any CYA, or does tap never contain CYA? The test uses 1/3 of the regeant that I have and don't want to do it if it's not necessary. I hope that's not a stupid question!

It's not a stupid question. There should be no CYA in your tap water, ever. There is no good reason for any municipal water utility district to add CYA and in fact CYA is dangerous if ingested in large quantities so it's not something that anyone would put into drinking water (and yes, this means you should not drink your pool water, except in an emergency).

The main components to test for your tap water would be alkalinity (which will be completely carbonate alkalinity since there is no CYA) and calcium hardness. pH would be interesting, but that could change by the time your pool gets filled and is probably near neutral anyway so primarily focus on figuring out how much calcium you need to add (as Calcium Chloride) and alkalinity (as sodium bicarbonate aka bicarbonate of soda). Adding these two items to neutral water will result in a pH near 8.0 at which point you'll need to add acid to get down to the pH you want (probably near 7.4-7.5).

If you want to be totally safe (and this is probably overkill) you can add the calcium chloride and sodium bicarbonate in portions as your pool gets filled. However, I noticed that our own pool got filled first and then had chemicals added and didn't have a problem even though technically the plaster and grout was dissolving (albeit slowly) into the water between the time it was getting filled and the extra chemicals were added.

Richard

[court475]

Thanks for your reply! So I assume then that I need to add enough CYA right off to bring it to 20-30ppm?

[CToon]

I would recommend starting out on the lower side. CYA can always be increased easily enough , while its not as easy to lower.

Plus , Its a Catch-22 type of thing going on. High CYA makes it easier to maintain CL levels , but higher levels of CL are needed for HIgh CYA. its anuff to make ya nuts I tell ya.

So try it low , if you find it too hard to maintain proper CL levels , bump it up a notch

[chem geek]

And don't forget to add chlorine right away to the water as you add it to the pool. That was probably assumed given that you were thinking of adding CYA right away, but I just want to make sure I mention it. Many municpal utilities have switched to using monochloramine instead of regular chlorine for disinfection. And yes, that means that one of the first things you may need to do after you fill up the pool is to shock it with lots of chlorine (exposing it to sunlight will also help break down the monochloramine).

Richard