How Do You Lower CYA?

[cheshamjim]

Here are my test results for my very first test with my just-received RS234 test kit:

FC = 11
CC = 0
pH = 7.2
Alk = 140
Cal = not tested
CYA = >100 (fills 1st inch of view tube, then dot disappears)

My CYA reading dictates that my chlorine content should be maintained between 8 and 15 ppm acccording to the Best Guess Table. I'd like to lower my CYA so that I wouldn't have to maintain such high levels.

I've stopped using stabilized products (dichloro and trichloro) and hopefully this stems the advance. But how do I get it to go down?

-Jim

[JohnT]

Drain water and replace, unfortunately

[Sherra]

I'd do a 50% drain & refill then re-test your CYA...if it's still higher than you want it, then do another 50% drain & refill. A 50% drain/refill should lower your CYA by 50%.

[cheshamjim]

Thanks, all. I was afraid this is the answer I'd get.

It seems that with my installation, I can only get by with a 30% drain at any one time. Think I'll wait until its time to close the pool.

-Jim

[Sherra]

One option is to get a really big plastic tarp (wide enough & long enough to cover your pool plus about 10 feet added to each measurement...just the cheap roll you can get at any home improvement place for a few bucks) and use that as a membrane between the two layers of water (the pool water beneath and the fresh water on top). You can theoretically do a 100% drain/refill that way without any damage to your liner. It's been discusses several times on the board. I don't know if anyone's actually DONE it on the group, but I remember seeing that someone had SEEN it done.

[cheshamjim]

Sherra, what an intriguing idea!

As I first envisioned this, one would introduce fresh water onto the membrane (tarp) which has been spread over the pool. As the water accumulates on the top side of the tarp it would sink and gradually displace the old pool water while complying with the sides and bottom of the pool.

Can this be? I am not a physicist or an engineer, but both the old and the new water would be essentially equal in mass, so it wouldn't seem that one could easily displace the other. Perhaps the old water is pumped out at close to the same rate fresh water is introduced to the tarp.

If this all worked out, how in the world would one remove the tarp once the pool is refilled? Have I correctly understood what you were suggesting?

If there is a tried and true procedure, I'd appreciate reading about it.

-Jim

[reneep]

Great Idea. I am sure it will work as over the winter when I cover my pool and we get a rain it displaces the pool water. When I siphon off the rain water, I have to add water back to the pool. Just cover with cheap plastic, fill then cut holes in it and pull it out by section... new water in pool to replace old ???

I am in the same boat and have been draining about 4 inches, refilling, letting the pump run to circulate and repeat. This seems much more effective.

[Watermom]

Fill with fresh water on top of the plastic sheet and pump out the old water from the bottom of the pool.

[let_her_flicker]

Another option is to run a high cya pool. You do not have to drain. Just make sure you have Ben's kit and keep the cl at the appropriate level. It should not be an issue. In fact, it may be easier as the cl will be used up at a slower rate because of the high CYA. Check your cya every two weeks and adjust accordingly.

If you are chlorinating with liquid bleach, you cya will go down. If you are using stablized tablets, it will increase. Just because you cya is high doesn't mean drastic measures. Let it go down naturally and you don't have to waste water.

Back on the old forum, this was discussed and sometimes advocated as a way to operate your pool. To do this you will need Ben's kit. I hope this helps.

[cheshamjim]

let_her_flicker, I like your suggestion. You say that as long as I don't use the stabilized tablets, the CYA will go down naturally. As of two weeks ago, the only sanitizer I have used is bleach (Chlorox from a Sam's Club).

I think that the fact I have used the tablets and powdered "shock" since my pool was first opened 4 seasons ago has caused my CYA problem.

As long as I know the CYA will go down on its own without these "stabilized" products I can wait. Patience, after all, is a virtue when trying get pool water right.

Thanks for your help.

-Jim