Green pool now blue after shock, what now?

[kluczenk]

Hi all, this is my second post to the forum and I look forward to learning a lot from everyone and contributing myself in the future. Here's my setup:

Inground freeform white plaster pool (~36x24, 33,000 gallon, 2 lights, slide, diving rock, installed April 2002)
A&A Manufacturing Quik Dek-chlor in-deck chlorinating system
Paramount in-floor cleaning system (Sta-rite 1.5HP pump)
Sta-rite 300 filter (attached to a 1.6HP pump)
Nature2 system (though I didn't get a new cartridge so it's empty)
Raypak RP2100 heater

The pool was VERY (neon) green yesterday so I got a bunch of shock from a local pool wholesaler and added 18 one pound packages of the product (68% calcium hypochlorate) and ran the pump overnight. This morning the pool looks very blue and cloudy though a bit clearer than when green. I have now added about 7oz of their super clarifier (1oz per 5000gal) and am waiting to see what happens. I'm an engineer at heart and don't like the idea of guess and check so I figured I would come here.

Also, the water here is quite hard as we are on well but I do not know what the pool was originally filled with. Lots of rain here near Chicago this year.

I am using test strips for checking chemistry and got:

pH - 7.2-7.8
FC - 10
Alk - 180-240
Stabilizer - 100

Please help! Any education is welcomed in addition to an answer on how to clear up the pool and keep it clear. Thanks!

[aylad]

I started to address some of this in your other thread about the chlorinator, and what you have posted here sort of confirms my suspicions. Your stabilizer is way too high from use of the trichlor feeder, and is the root of your algae problems. Another major problem that you have is that you're testing with strips, which are notoriously inaccurate, at best. For example, you're giving a pH reading of 7.2-7.8. That's the whole spectrum of "normal" pH readings, but you really need to narrow it down to one reading to be able to accurately adjust it. Also, while your strips measure stabilzier of 100, it can very well be way higher than 100, which will cause you a multitude of problems. If you'll look at the chart below, you'll see that as your stabilizer level increases, so must your chlorine.

Stabilizer . . . . . . Min. FC . . . . Max FC . . . 'Shock' FC
=> 0 ppm . . . . . . . 1 ppm . . . . . 3 ppm . . . . 10 ppm
=> 10 - 20 ppm . . . . 2 ppm . . . . . 5 ppm . . . . 12 ppm
=> 30 - 50 ppm . . . . 3 ppm . . . . . 6 ppm . . . . 15 ppm
=> 60 - 90 ppm . . . . 5 ppm . . . . . 10 ppm . . .. 20 ppm
=> 100 - 200 ppm . . . 8 ppm . . . . . 15 ppm . . .. 25 ppm

So with a stabilizer level higher than 100, you must shock it up to 25+ ppm and hold it there to completely clear an algae bloom, but then must never let the chlorine go below 8 ppm or you're inviting another one! Also, if 10 is as high as you're chlorinating to now, you probalby haven't completely cleared your current bloom, which will make it reappear that much faster once your chlorine falls again. You need to get your chlorine up to 25 ppm and hold it there by testing and adding more chlorine 2-3 times daily, or as often as you can. You need to keep it at 25 until the water clears, you have no combined chlorine, and you're not losing any chlorine when testing at night after the sun is off the pool and again in the morning before the sun is on the pool. After that, then you can let it drift back down. You didn't give a calcium hardness reading, but that also could contribute to cloudy water issues and potential scaling, if your other levels are not inline--but you have no real way of knowing unless you're using drop-based testing.

So...as far as clearing up the "cloudy" right now, keep your filter running 24/7, because the chlorine kills the algae, but the filter is what removes it from the pool. Also, get the chlorine back up to 25 and hold it there as I described above. I highly suggest you buy a drop-based test kit (we recommend the Taylor K-2006, but at least the WalMart 6-way is better than nothing) and do your own testing. I don'[t know how feasible partial drain/refill is for you, but I very highly recommend that you drain and refill at least 1/2 of your water in order to drop that stabilizer level down and get it more manageable. IN any event, I wouldn't use the pucks anymore at this point. Also, depending on what your calcium level is you may not need to increase your calcium anymore, so I would suggest that you switch to just plain, unscented, generic bleach for chlorination.

Janet

[kluczenk]

Thanks so much again Janet. So based on your response it sounds like there is no way to chemically alter the pool to reduce the stabilizer and keep my required FC levels at a reasonable amount. My only solution would be to drain and refill part of the pool? Is that accurate? What about rainwater and evaporation over time, will that slowly reduce the stabilizer levels?

I'll stop with the calcium-based chlorine treatment and switch over to plain bleach. The water here is hard and if that was used to fill the pool originally there is probably quite a bit of hardness.

What about the alkalinity being so high? Is that a major problem and what can I do to resolve it?

Hopefully I can keep learning a nugget or two of info from each post till I'm self sufficient. As knowledge is power I'll start with getting accurate readings of the chemicals.

[aylad]

There are only two ways to drop the stabilizer level--one is to turn it into a green, swampy mess and let the bacteria consume it (I'm guessing you don't want to go that route! ) and the other is to drain and refill water. The only other thing you can do is to up your minimum chlorine to compensate for the CYA being so high. If your CYA is truly at 100, then it just means that when you shock, you go to 25 ppm and that you never let your chlorine come down below 8 at any time. However, usually when CYA measures at 100, then it's usually over, sometimes by 2 or 3 times. In that case, there's not really a way to measure how high your chlorine has to be, so you're going to end up fighting the algae all summer. Over time, splashout and refill will help lower it, but very, very slowly. Evaporation doesn't help--as the water evaporates, it just concentrates the CYA in the water and dilutes it again when you add new water.

Your alkalinity is high, and can create scaling conditions when your calcium is high, as well. The process to ratchet the alk down without completely throwing off your pH is outlined in the "alkalinity and calcium" forum. It's titled "how to lower your alkalinity" and is stickied at the top of the forum.

Take some time and read through the forums, especially the stickied ones written by the mods and Pooldoc, the owner of this site. There's a whole lot of information around here, and at first it can seem overwhelming, but caring for your pool is so much easier and less expensive than people think it is--WHEN you understand the effects on your pool of the things that you put in it.

Janet

[kluczenk]

Sounds good, I'll start reading around a bit more on the stickied items. One other question as I think I at least have a direction for the time being. Now that the water is a bluish color but still seems cloudy what can I do to get things back to a clear/blue rather than a milky/blue? I'll continue running the filter and keep the chlorine high by adding plain bleach. I have some water softener/mineral additive, should I add that?

[aylad]

No additives, just good filtration and adequate chlorine levels. It takes longer than a day to develop the kind of algae bloom that you had (and I'm not convinced you've completely killed it yet--cloudy water is often THE early announcement of an algae problem) and it's going to take longer than a day to clear it up. Bump the chlorine up to 25 ppm and hold it there as I described in the other post, and keep the filter clean and running. Oh--there IS one more additive that we do recommend very often--POPP (pool owner patience and persistence). That one is usually the key to everything!!

Janet