Algae in pool

[newdude]

Hey ohaya!! Always ask if you’re unsure. If you can do it pleasantly like you’ve done, well that’s even better. We’d much rather square away a plan in theory than have to fix a new problem. Both for your sake and ours.

so you can do many patrial drains, but they lose efficiency greatly so the excess water costs become a factor. If you drain once, Your 200 CYA is 0. If you drain 10% ten times you still have a CYA of 69. Which will require *7* more 10% drains to reach a CYA of 33. 33 will round up to 40 and probably still be a hair high after 170% water exchange in bits.

 

[ohaya]

Hi Rancho,

Our pool is not exactly rectangular (it's shaped like a peanut ) - but approx. dimensions are 22x42=924 sq ft.

So 1' drop would be about 6911 gallons

Pool is 28000 gallons, so that would be about 25%?

I can do it in early evening, then maybe fill it that night?

Then measure the CYA when it is full again?

 

[newdude]

25% is good. And it will lower your CYA by 25% to 150. The next 25% drain will only lower the 150 by 25% to 112. Each time it gets less productive. It works but takes more tries to get to the same result. Sometimes many more tries. Which can be a good thing when you are worried about your shell, but it takes a lot of work.

consider a water exchange instead of a drain. In a nutshell, You let science help and drain the colder heavier water at the bottom while you add warmer water to the top. Or vice versa depending on your local conditions. If done evenly the pool level stays the same (or close enough) the whole time. Read here : #3.5

Draining - Further Reading

www.troublefreepool.com

 

[Rancho Cost-a-Lotta]

There's a pool volume calculator on the Old Pool Math page. Entering your OVAL width and length at a depth of one foot shows 6,100 gallons. As a rectangle, it shows 6,900 gallons. It's likely between there somewhere. As @Newdude indicated, partial exchanges are highly inefficient, so drain as much as you feel comfortable with each time.

You can test after the partial drains, but with a diluted sample and a CYA of 200ish, you probably won't be able to interpret much of a change on the sample.

 

[Rancho Cost-a-Lotta]

One thing to keep in mind...as you drain below steps and ledges, your surface area decreases. Take that into consideration as you move forward.

 

[ohaya]

Thanks. I know this might not make sense, buy what I am fighting here is our pool guy says ignore the cya and if the FC is good then should not have algae and my wife believes him and doesn't want drain.

 

[newdude]

The more CYA you have, the more it ‘protects’ the available chlorine in the pool. So the FC is there but unable to do its job. Like you’ve seen with your own eyes. The pool store / guy keeps adding stabilized chlorine which makes the CYA even higher and eventually calls it ‘chlorine lock’ and tells you that draining is your only option. They sell you the initial balance chems for the fresh water and start jacking them up all over again. It’s a vicious cycle but enough time goes by that the pool owner thinks the system worked for 2 or so years so they keep at it.