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! :eek: ) 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

[kluczenk]

Many thanks. I'll go get some store-bought bleach to keep the chlorine level high and throw in a little POPP for good measure! On a related note I've purchased the Taylor self-test kit. I'm hoping with a little TLC from Poolforum I won't feel like moving out of this house because of my costly pool. I'll keep you posted on progress.

[aylad]

Buying your own test kit will make taking control of your pool SO much easier!!!

Let us know how it's going....

Janet

[kluczenk]

Test kit came and I did my first set of tests! Unfortunately the pool is getting green/cloudy again. I don't want to add any more shock and increase the stabilizer any further but have no idea how much bleach to be adding. I posted in the water treatment/balancing section of the site with the following data:

FC=0
pH=7.6
TA=200
CH=325
CYA=70
Water Balance=.575

I've added a bit of bleach since last week but clearly not enough. How much do I need to be adding to my 33,000 gallon pool to keep it high enough for the stabilizer? You can reply here or my post in the other section.

[kluczenk]

Sorry for the double post, here are the stats from the original message:

Hi all, I've posted previously in the algae section and received great responses. I was able to clear my murky pool but in waiting for my Taylor test kit to arrive it has started to go green on me again. Please take a look at these results and let me know how to proceed:

FC=0
pH=7.6
TA=200
CH=325
CYA=70
Water balance=.575 (using the included wheel)

I have a 33,000 gallon chlorinated plaster pool and due to high levels of stabilizer have been told that I should just use regular bleach to chlorinate the pool or be forced to empty and refill to reduce stabilizers (which won't happen this summer). How much bleach do I need to add to the pool to get my chlorine to a high level and kill off the algea. I don't know whether to go out and buy 3 or 4 bottles of bleach or 20 or 30. I'll obviously continue to run the pumps and will scrub and vacuum the pool as well. Please help to clean the pool back up.

[aylad]

If you'll look at the best guess chart in one of my above posts, it tells you that to shock a pool with a stabilizer (CYA) of 75, you need to raise your chlorine up to 20 ppm and keep it there by testing and adding more 2-3 times daily until the water clears up again. To get to 20 ppm, it will take 11 gallons of 6% bleach. After that, when you're re-testing to add more, each 1/2 gallon of bleach will raise your chlorine by 1 ppm, so you can use that as a guide to figure out how much more to put in each time. Keep the filter running, brush the pool daily. Keep it at 20 ppm 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, just like you did before. However, this time, DO NOT LET THE CHLORINE DRIFT BACK DOWN BELOW 5 PPM. Because your stabilizer is so high, you must keep it higher than 5 ppm to keep from having to repeat this cycle over and over again. This means that you must test the water daily, and add chlorine (bleach) as needed (probably daily, or at least every other day) to maintain your chlorine levels and not let them go to zero again. This is an ongoing process, not a one-time cure.

You want to enjoy your pool, not just spend the summer treating it! :)

Janet

[kluczenk]

Thanks again Janet. I assume you're using acquired knowledge or something like poolcalculator dot-com to come up with the amounts. I just found that a short bit ago and got back from Costco with a whole mess of bleach that I'll add this evening. I'm looking forward to next year and not messing up my CYA so I don't have to maintain such a high chlorine level to keep the algae at bay! Till then it looks like I'll buy stock in the bleach companies and keep adding...

[aylad]

I'm using Bleachcalc--one of the original chem calculators that was developed by MW Smith several years ago.

I think you'll find that even with the high CYA levels, if you don't let the chlorine drop down so low, then it really won't take any more bleach to maintain the higher levels than it would in a low CYA pool, because although you have to reach a higher level, you're also starting at a higher level. It doesn't take any more bleach to go from 0 Cl to 10 than it does to go from 10 Cl to 20. The problem you're seeing is that if you let it go all the way down to 0, then it take a BUNCH of cl to go from 0 to 20!!

I intentionally run my pool at a CYA of 80-90 for that same reason, because I live in a very hot, humid climate, and my pool is in full sun from sunup to sundown. I actually use the same (or maybe even a little less) amount of bleach as those with lower CYA pools, but only have to add it every 2 or 3 days because the stabilizer protects it so well from the sun. But it only works because I keep it consistently above the minimum laid out in the Best Guess Table. It also works for me because my pool stays open and chlorinated year round, so I don't have to deal with the CYA breakdown problem.

There is something else you need to be thinking about, as we get closer to the end of the season, which is the other consequence of too much CYA in the pool......depending on how you treat the water through the winter will have an effect, but basically that CYA will do one of the following:
1)Remain present in the water and you can resume the high Cl routine next year
2) Lower gradually over the winter IF you're not using trichlor and IF you keep it chlorinated enough to keep algae out and IF you either purposely drain some or do many backwashes or
3)If allowed to go green, the algae and accompanying bacteria may break the CYA down so that you actually start the year with a CYA of 0, but one of the byproducts of that breakdown is ammonia, which creates a HUGE chlorine demand upon startup of the pool that takes the same amount or even more of bleach to overcome.

So--it's not magically going to go away, you're still going to have to make a decision about either a partial drain or taking your chances with it breaking down over the winter. Personally, I would take the opportunity with every backwash to dump as much extra water as you can each time--believe it or not, it will slowly start to come down.

Janet