Using Bleach in the Pool

[Schooled by Pool]

As of last night the PH is at 7.6, Chlorine 3.0, the CYA test I was not able to administer, because the test kit I inherited is missing that componnet right now. I used the test strip, which agreed with the test kit #s, and gave me a "very high" stabilizer reading or 150.

I am told the pool is 25,000 gallons, the filter is a Hayward sand filter S220T, with a Hayward super pump 1.0 HP.

Pool is cloudy. Seems to have lots of dead algae in it, which moves/billows up when touched and is no longer clingning to the walls or floor. I suppose I will have to vacuum to waste again tomorrow and see what happens.

[aylad]

If you see the filter pressure rising, then the filter is doing its job in filtering out the dead algae. Remember, chlorine kills it, then the filter (or vac'ing to waste) removes it. However, you won't know if you've killed it all off until you can test chlorine after the sun is off the pool, and the next morning before the sun is on the pool, and lose less than 1 ppm of chlorine in the process. However, to do that, you are going to need drop-based testing--strips simply are not accurate or reliable enough to use for this purpose. Also, strips do a very, very poor job of measuring CYA--they can usually tell you if there is, or is not, CYA in the pool, but you need an accurate CYA level before I can begin to tell you where your chlorine level needs to be for shocking purposes,. The Best Guess table that Carl referenced above will explain that more fully, but in order to access it you need to log out to the main forum page, to go the "Using chlorine and chlorinating chemicals" subforum, then open the second sticky for the Best Guess Chart.

[Schooled by Pool]

I have drops and use them for the chlorine, ph, etc. But not CYA, because the test kit is missing a piece. Also, it is probably not the best kit (pool time), and it is probably old. I will replace on Monday. In the mean time, I will test again tonight, which will be 24 hrs after last test. I am grateful for your help. Thank you.

[Schooled by Pool]

I will also test in the morning, and compare to the evening test. Thank you.

[aylad]

If you don't lose any chlorine, then you just need to filter out the dead algae. However, if your guesstimate of a CYA at 150 is anywhere close to accurate, it won't be long before you do have algae growing--in a pool with CYA over 100, you need to be keeping your chlorine at a minimum of 8 ppm--normal operating range for you would be 8-15 ppm, with a shock level of 25 ppm. In a 25K gallon pool, each half-gallon of 6% bleach will raise your chlorine level by 1.2 ppm, just to give you an idea....if your chlorine is now at 3 ppm, then to get to 8 ppm you would need to add 2.1 gallons of 6% bleach.

That's why your CYA level is so critical--it determines how high you have to keep the chlorine in order to keep the pool clear and clean.

[Schooled by Pool]

Well, I tested it tonight and the chlorine was down to 2 the ph was down to 7.4 (according to the drops) and the stabilizer on the test strip dropped to the appx 100 reading on the strip. This is 24 hrs after I put 3 gallons of bleach in the pool (6%). For that matter, I put 3 gallons in the night before too. Should I wait to test in the morning to see where I am at or add more bleach just to be safe?

[aylad]

The idea behind testing to see if you have a chlorine demand is that chlorine is consumed by two things: sunlight and pool goo. You can't really judge by looking at a 24 hour chlorine consumption whether you still have algae, because you don't know how much of the chlorine was consumed by the sun and how much by the goo. That's why you need to test at sundown after the sun is off the pool and again in the morning before the sun hits the pool if you're trying to establish whether your algae is all dead. You are always going to lose some chlorine during the day, due to the sun.

With a CYA at 100, you still need to keep your chlorine at a minimum of 8 ppm, otherwise you're inviting algae to start. You'll need to look at your results taken at night and in the morning to determine whether you still have an algae problem or just dead algae that needs to be filtered out.

If your chlorine is at 2, you need to add more bleach to get up to at least 8 ppm--but if you determine that you still have overnight chlorine consumption, then you need to shock it up to 25 ppm.

[Watermom]

Maybe Janet has already mentioned this to you in your thread and I just missed it when I scanned through it but you need to buy a good kit. Especially if your CYA is over 100 like you think it is, you'll have to run higher chlorine levels than the kits you'll be able to buy locally will be able to test. You need to buy the Taylor K-2006 or 2006C kit which you can find in Janet's (Aylad) signature block in post #2 above. It can register chlorine levels up to around 50ppm I think as opposed to around 5 like most kits.

[Schooled by Pool]

@ aylad, the test this morning showed chlorine between 1 & 2. LAst night was 2, but the lighting was different, in the room, so maybe that affected the change in the reading? Ph remains at 7.4 and the CYA remains above 100, at approx 120.

Water in the pool remains cloudy.

@Watermon, I am going to buy at Taylor Kit. I tried to find something locally when I came back into town, as a stopgap, but was shut out.

[Schooled by Pool]

Tested tonight (had to go away for the w/e). It was 2 for chlorine. 7.4 for ph and the CYA was over a hundred. I had to use an old tube for the CYA test and the reading #s only went up to 100. I am guessing it was over 120 based on the spacing of the lines, but it is a guess. I will test again in the morning.

I have 9 gallons of 6% bleach waiting to go in the pool if necessary and can get more. The pool is slowly, very slowly, clearing (1.5 weeks after initial shock treatments), but is still cloudy, especially in deep end. No new algae has popped up. I can still see dead algae on the bottom.