How Do You Lower CYA?

[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

[waterbear]

It can take a very long time for the CYA to go down on it's own, expecially if you have a cartridge filter. CYA will only go down by dilution under normal circumstances. This means refilling from splashout, backwashing a filter, or draining and refilling. Evaporation will merely concentrate it and it will dilute to where it was before when the evaporated water is replaced. Using bleach or any other non stabilized chlorine will not make it go down. However, using trichlor or dichlor will make it rise since with every use of these products you are adding more CYA!

BTW, most powdered shock is Cal Hypo (calcium hypochlorite) and is non stabilized chlorine. Dichlor is ususally only recommended for shocking spas which get drained and refilled every 3 months. It is ususally used in poos for normal sanitation.

[gordyjamz]

Last year I was running with cya of 60-70, but when opening this year I noticed it was down to 30. This was before I refilled back to normal level, at which point it was down to under 20. I had to actually raise it. I think it goes away when the water sits over the winter. So it may be less hassle to just run with higher cl level this year and see where you stand next spring and adjust accordingly then.