green pool with high chorline

[TominTx]

I have a green pool problem that I am trying to beat. The pool is 20 by 40 with a 12 deep end 3 feet shallow end I used an htc test kit and it showed the Caroline in the orange area but there is a ton of algae present. So I took a water sample to leslies Pool supply and here are the numbers
Fac 5
Tac 5
Ch 200
Cya 100
Ta 90
Ph 8.0
Tds 1000
Pho 300

Please help with suggestions. Tom

[Watermom]

Hi and welcome! The most likely problem to me is the high CYA reading. Since test kits can't differentiate past 100, it could very well be much higher than that. When you have a high cya reading, you have to run higher than normal chlorine readings to keep algae at bay. Most people don't realize this and even though they are keeping their chlorine levels at the same level they always have, they start having algae problems.

I'm going to offer two options.
#1. You can keep the high CYA levels but you'll have to run extra high chlorine levels as a result. (See the "Best Guess" table in my signature below.) To clear up an algae bloom in a pool with a CYA of 100+ would require maintaining a shock level of 25ppm. And, then when the algae bloom is finally cleared up, you'll need to keep your chlorine level between 8-15 all the time or else the algae will come right back.

OR

#2. You can do a partial drain and refill to try and lower the CYA. Depending on how high the CYA actually is, it can sometimes take a couple of partial drains and refills to get it to a more manageable level. Do NOT totally drain your pool however. Doing so can cause it to pop out of the ground, especially if you live someplace with a high water table. You can probably safely drain half, but you want to make sure your shallow end still has plenty of water in it.

Decide which of those two options you want to do and then somebody here can give you further advice. Your pH is too high at 8.0. You'll need to use some muriatic acid to lower it down but we can help you with that after you decide on 1 or 2 above. Don't worry about the TDS or Phosphates.

By the way, I assume this is a gunite pool? Can you also give us the volume?

Lastly and most important, you need to get a good test kit, especially if you decide not to do a partial drain and refill. You're going to need a kit that can measure high chlorine levels. The only one we recommend is the Taylor K-2006 or 2006C which is the same kit with just larger quantities of some of the most used reagents. You can order it from Amazon from the link in my signature line below, And, the Pool Forum makes a little money on the sale which helps us to be able to stay online.

[PoolDoc]

Two things: lower your pH, and raise your chlorine. You also need to run your pump and filter 24/7 till you've got everything cleaned up.

You need to do both, but unless you have access to dealer testing with a pH meter, you can't get an accurate pH reading once you lower your pH.

So, go to Lowes or Home Depot and get a gallon of muriatic acid. Use gloves and glasses, and avoid the fumes, but add about 2 quarts (1/2 gallon) to your pool, tonight if possible. Wait 2 hours (or till the AM) and retest. If your pH is not below 7.6, add the rest.

Once you've got the pH below 7.6, you can start raising your chlorine. Add 12 gallons (no typo -- I mean "12") of 6% household bleach to your pool. You can pour it into the deep end, but make SURE your pump is running.

Do NOT try to fix anything else - TA, CH, phos.

Read the BBB method and Best Guess pages as you have time. Repost, as you get test results or things change.

Good luck!

Ben

PS: Lisa (Watermom) was posting as I was writing. What she's telling you is also correct, but it's a little longer term view than I'm taking. I assumed you'd want to clear up the water first and then address the high CYA. But, you can make that choice now, if you like. However, it will take high chlorine to remove the algae when you have high CYA. The "Best Guess" pages explains why this isn't necessarily a bad thing.

[CarlD]

Pour the Muriatic Acid SLOWLY into the return stream and be careful not to breathe the fumes. That way the acid will be diluted quickly and won't sink and damage your liner.

Carl

[madwil]

+1 to what Carl said- I've been playing with chemicals for almost 40 years, and yesterday sloshed the MA a little; didn't spill, but the fumes were pretty potent!

[CarlD]

I inadvertently sniffed a bottle not knowing it was MA a few months ago...it was a rough few minutes and I was lucky for having been incredibly dumb! REALLY dumb. NEVER do that!

Carl

[TominTx]

Thank you all so much for your advice. I went to Home Depot and poured in the muratic acid into the return stream at the deep end.

Is there a way to know how high the cya levels really are? I am afraid that if they are really high it will cost a fortune in bleach, but on the other hand it costs $400 to drain and to fill it up again. I will order the test kit from your signature.

I have taken before pictures and will post the after ones when I get this cleared up.

Tom

[madwil]

it's not real accurate, but you can do a "shotglass" test with CYA...
1 shot pool water
1 shot distilled water (tap would probably be ok, since there shouldn't be any CYA in your tapwater)
then do the CYA test and multiply by 2 (if you still read 100, you'd have to dilute more- it could be over 200!)

[CarlD]

Distilled water is really important for the shot glass method when you are testing chlorine, as tap water frequently has chlorine in it.

While it's probably better for the CYA test, I think madwil is probably right that tap water should be OK, if you don't have distilled.

(BTW, Steam Distilled water is available at most supermarkets and drug chains)

Carl