White Flakes From Pool Return Clogging SWG?

by Elle

White Flakes From Pool Return Clogging SWG?

by Elle
(Modesto CA)

I have a aqua rite salt water generator. My pool is about 13,000 gallons with a raised spa. I have included as much info as possible. I don't know my calcium hardness but I can tell you that our water is very hard. I live in the Central Valley of California. Here is my situation:

6-13-14. Everything with SWG was working fine. Salt level was 3000
6-14-14 Had a pool service remove buildup from our tile line in both the pool and raised spa. This created a lot of cloudiness/debris for a couple days.
6-19-14 Same guy came out and cleaned the filter and cell.
6-19-14 to 7-3-14 Noticed a lot of white flakes coming out of pool returns.
7-5-14 Salt down to 2600 flashing low salt and check cell
7-5-14 I opened up the cell, a good amount of junk in there. Cleaned it and when I started up SWG again reading went back to 3000.
7-6-14 I turned my filter on manually and a TON of white flakes came out of pool return when the SWG started generating. Salt heading back down to 2800 even after I added about a third of a 40 lb. bag.

So... at first I thought the pool service guy did not clean the cell (but I've known him a while and he is a stand up guy so that didn't make sense.) I
My next suspicion is that all the calcium hardness that was scraped off my tile is now "swimming"around the pool and settling in the cell when the system shuts off. It seems to build quickly and make my cell go into shut down mode once it is sufficiently gunked up.

Has anyone had this happen? Am I on the right/wrong track? What is the solution?

My numbers yesterday were:
FC 4.0
TA 90
PH 7.8
CYA 110

Today my PH is down to 7.6 and FC is at 5.0.

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Thanks for the question Elle

I'm going to try to break this down as best I can. First is your pH. It's a bit too high at 7.8. You want to try to keep it at 7.4 - 7.6. This will be more difficult with a CL generator as they tend to increase the pH at a slightly faster rate.

The white flakes that you're dealing with is more certainly the calcium carbonate after the cleaning. If your CL cell is reverse polarity then one side is being cleaned while the other side is producing CL. The flakes are then coming off into the water. Living in CA with hard water is something you can't get around unless you have pool water trucked in. Be sure you're not using granular chlorine (calcium hypo). This will not only raise the pH but add hardness to the water.

Next is your CYA. It's a bit high at 110ppm. Normal range is 30 - 50ppm. There's no way to reduce that but to do a partial/full drain and refill. You're running the risk of having a green pool with a CYA that high. But on the bright side you can have a slightly higher CYA with a salt pool when you allow the TA to come down to 70ppm and keep the CL between 4 - 5ppm.

You might want to consider adding borax to 50 ppm to your water. This acts as a secondary pH buffer and has been found useful with CL cells. It's 113 oz. of borax to raise the level 10ppm per 10k gallons. This is nothing more than 20 Mule Team Borax than can be found in the grocery store. The reason it's good with CL cells is because of the out-gassing that precipitates the pH rise with a CL cell.

You'll need to have muriatic acid on hand as adding borax does raise the pH in the pool but the borates remain as a buffer. If you choose to do this remember to make small adjustments rather than on large one. It's 20 oz. of acid to lower the pH 0.2 per 10k gallons. Remember that when you add the acid it will hit both the TA and pH. The CL cell will naturally increase the pH.

So to sum it up I'd reduce the TA to 60 - 70ppm. Normal range is 80 - 100ppm but a salt pool can get away with a slightly lower TA. Keep the pH 7.4 - 7.6 and no higher. Add enough borax to bring the level up to 50ppm, keep the CL generator clean and FILTER and BACKWASH when needed.

I hope this has answered your question to your satisfaction.