Green Salt Water Pool

by Angela

Just wanted to be sure I'm understanding right. So treat it like a regular pool till it's clear again? I have to clean my salt cell about 1 time a week with vinegar to keep it working cause it's well water, not sure if that has anything to do with it.

It has been over 100 degrees for over 30 days & I just can't seem to keep the pool chlorinated...which caused my green!

So just use regular chemicals to get it back clear or no?

Thanks for the question Angela

Yes you can use regular chemicals to get the pool back to normal. You would shock the pool as you would a normal chlorine pool, but you'll need to first turn the salt cell off.

I'd like to have your complete chemical readings:

Chlorine, CYA (cyanuric acid/stabilizer), pH, Alkalinity, Calcium Hardness, and Metals (iron and copper).
It makes troubleshooting much easier and the process of clearing up your pool will go much faster.

You can get this done at your local pool store.

I'd encourage you to get a Taylor FAS-DPD K-2006 pool test kit.

Pool Water Testing

Water Testing Kit

Without these numbers I'm just guessing at what the problem is. You have well water which means the metals could be high.

If the pool can't keep chlorine there's a possibility that you have either too high or low cyanuric acid (CYA/stabilizer) or possibly high pH but I can't know for sure without the actual readings.

Get back to me with the chemical numbers and I'm sure I can help.


Comment By Angela
Date: August 7, 2011

Thank you for getting back to me. I took a water sample to the pool store...chlorine 0.00, PH 8.02, Calcium hardness 215, ALK 149, CYA 8.

They said to "slug" it, pour in 2 cups Muriatic acid let sit with pump off overnight. Next day...turn pump on, pour in another cup of Muriatic acid, let pump run 2 hrs or so.

Then add 1 lb of Chlorinating granules & put chl tabs in skimmer basket....5000 gal above ground pool, sand filter & chl. generator.

They were all out of the phosphate testing stuff, so they could not test for that, I think it might be high because I never get a chlorine reading when I use my test strips at home. I can sometimes smell chlorine, but it never shows on the strips.

I know that if there is too much phosphates in the water, it will not hold the chlorine, so that could be a problem too.
I'm gonna take another sample in Monday when I go to get the CYA (I think he forgot about it & I did too till I was working on it Sat. morning)

I did all of this and the water is not as green, but it's still green. Am I headed in the right direction?

Also, I have to clean my salt cell with vinegar about once a week it seems like, is this normal? Will all these chemicals mess up my chlorine generator?

Thank you again for all your help! My pool store ppl are not very familiar with the salt systems, so I just wanted to be sure that I'm doing the right things to fix it. lol!

Comment By Robert
Date: August 7, 2011

Thanks for the follow up Angela

You're my favorite visitor today. A great follow up and excellent readings. It makes life so much easier for me.

Your chlorine level is too low, which you already know. The pH is a bit high. It should be between 7.6 - 7.8ppm. But for now we'll get it down to 7.2ppm. Chlorine runs better at a slightly lower pH. Alkalinity (total alkalinity/TA) is high at 182.

You'll want to get it between 80 - 100ppm, 120 being the top. Calcium is fine so don't touch that. CYA is 8. It needs to be between 30 - 50ppm and the chlorine between 1.5 - 3.5ppm. This is for normal maintenance, but clearing up a green pool is different.

I don't like calling that the "slug method" but for clarity, it works to lower the alkalinity without much happening to the pH. Both are high and need to come down, but it depends on how you add the acid.

Acid in one spot with the pump off decreases the alkalinity. Acid broadcast around the perimeter of the pool with the pump running decrease the pH.

Swimming Pool pH Levels

Pool pH

Pool Alkalinity

Total Alkalinity

While clearing up the pool you'll want to keep the chlorine generator off.

You can add acid to one spot with the pump off for the alkalinity, but you only need it off for about 3 - 4 hours, then turn if back on. Do this in the evening, then retest the alkalinity and pH in the morning and make another adjustment if needed.

Always wait for 1 full turnover of the water before retesting. This is normally about 8 hours. Very gently sweep the bottom and sides during the slug method. You want to break up any hot spots of acid. Don't disturb the acid too much.

Now you need to shock the pool. You have no CYA so you need to get some in there. Use Dichlor shock. This is a stabilized form of chlorine. For 5000 gallons, 11oz. will raise the chlorine level to 10ppm.

You'll want to use a bit more (maybe 1 lb.) to get it to 12 - 15ppm. Go a little over, it's better than not hitting the 10ppm mark. Shock at night, then retest the chlorine and CYA in the morning. You'll see how much chlorine has been used through the night. Keep filtering 24/7.

Be careful when using Dichlor as it can get out of hand quickly. For every 10ppm of chlorine added with Dichlor, you'll raise the CYA by 9ppm.

For every 10ppm of chlorine added with Trichlor tabs you'll raise the CYA by 6ppm

You CYA might be at 20ppm (or so) at this point. Shock it again with Dichlor and retest the chlorine and CYA after 1 turnover.

When it gets to 30 - 40ppm, stop using Dichlor and switch to regular liquid chlorine. Don't use regular chlorine granules to shock because it has a pH of 12. If you shock with granules the pH will go through the roof and you'll start all over again.

About 3 hours after you shock you can add acid to lower the pH. Be sure to test the pH before making any adjustments. It may have come down already.

The trick in clearing up a green pool is to get the TA and pH in line and keeping the chlorine level above 12ppm for a period of time. That's why you shock in the evening, retest in the morning, then shock again.

If the pool guy told you that having a high phosphate level will render the chlorine less effective, print this post and have him read it out loud to you:

High Phosphates Over 1000 & Cloudy Water

Get a chlorine tab floater. They're about $10. Don't put tabs in the skimmer. They keep dissolving and when the pump turns back on the system will get a high dose of acidic water. The pool will already be getting CYA with the Dichlor.

Use chlorine tabs in a floater to maintain the CYA. Get into the habit of using a float, not the skimmer, for your chlorine tabs.

To clean the salt cell, try a 4:1 mixture of muriatic acid and water. 4 water and 1 acid. You need to let this soak for about 5 minutes, when rinse with clean water.

Ask your pool store if they have a plug for the end of the cell. If not, you can call TMI Salt Pure. This is the company I use. Or your salt cell manufacturer.

Cleaning it once per week seems a bit extreme. I clean the salt cell at the Y only once per month, and this is with 5000 swimmers per month.

For a normal home salt pool, you should only need to clean it about 3 times per swimming season; beginning, middle, and end. In Arizona we had very hard water, between 300 - 400ppm.

This might be the case for you in Texas. If your fill water is hard, you'll find that cleaning the salt cell often is necessary. Get the fill water tested as well to confirm this.

Here are my salt pages:

Salt Water Swimming Pools

Chlorine Generator

And there's lots of good info. on the Q&A page in the salt pool and chlorine generator categories:

Swimming Pool Questions and Answers

Remember to keep the chlorine level above 12ppm. This is the key point. Test and retest morning and night. Take a water sample to your pool store for analysis after every turnover of the water, or as often as you can.

And remember when the CYA get between 30 - 50ppm, stop with the Dichlor and use liquid chlorine.

You'll know when the algae is dead because the pool will turn a grayish/white and the chlorine level will only come down 1 - 2ppm from the evening test to the morning test.

Hope this helps and have a great Summer. Let me know how it turns out for you.


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