More white flakes appearing

Total hardness and calcium hardness in pool water.
Scale, calcium buildup, hard water and scaling problems.
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Joined: Wed 08 Aug, 2007 11:22

More white flakes appearing

Postby HBLabs » Wed 08 Aug, 2007 12:31

I'm a newbie, and maybe that's my problem, but here goes:

We are first-time pool owners. We have a 40,000 gallon pool. Originally the pool was chlorine, which we converted to saltwater about 3 months ago. The two weeks was great, but then we started seeing white flakes in the spa. We thought it was from the solar heater and somehow by converting the pool, it had changed the chemistry and we were getting calcium flakes. I also noticed a white line become more apparent on the rocks where the waterline is. I'm thinking that is scale. It's become thicker and I can't even scrub it off with a metal brush.

We also were having a hard time keeping the chlorine level where it needed to be. We were shocking the pool each week and when we would bring the water in to be tested by Leslie's, it would read as though we had no chlorine in it.

We are now using a pool company that checks the chemical levels in our pool each week. This morning they said the alkalinity was up, so they added acid. Is there something specific to my problem that I should have them check for each week? They don't know what to make of the flakes.

We have 2 labs that love to be in the water every chance they get. We were told this is the reason why we don't have chlorine in the pool. I guess their fur soaks it all up. I turned up the level on our salt monitor to 3200 and I think we've taken care of that. When they go in the pool that day, we run the system until we go to bed that night or we run it all night depending on how long they were in the pool.

The pool company recommends that we drain the pool to get rid of the flakes, but because we live out here in Vegas, we can't do that for at least another month or two. Is there anything else we can try in the meantime or is that our only option? 40,000 gallons is a lot to drain and fill up, so I just want to make sure I have researched all our options. In the meantime, we're just getting more and more flakes. My husband doesn't want to swim in it not knowing if it would be harmful if swallowed - he swims for exercise.

Sorry for the long post, but figured it best to know all the factors that may be the cause of our problems. Any help is greatly appreciated!


white flakes

Postby littlepuppy » Sun 30 Dec, 2007 19:36

we are having the exact same problem, did you happen to find a solution??
chem geek
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Postby chem geek » Sun 30 Dec, 2007 21:11

The flakes are probably calcium deposits forming on the cathode in the SWG (the plate where hydrogen gas is formed) as the area near the plate becomes very alkaline (the pH rises) so tends to form calcium carbonate deposits. The SWG reverses polarity periodically and this then removes these deposits, but they end up looking like flakes coming out of the returns.

The best way to solve this problem is to prevent the formation of the flakes in the first place. That means running your pool with a slightly negative saturation index. That means either a lower Total Alkalinity (TA), Calcium Hardness (CH) or pH. However, since the hydrogen gas bubbles from the SWG aerate the pool water, this will make the pH of the pool tend to rise over time and the way to reduce that problem is to reduce the TA so I would say you should significantly reduce the TA to solve both problems (flakes and rising pH) at once.

You can lower the pool's TA level by following the procedure in this post. You should also consider raising the Cyanuric Acid (CYA) level to 60-80 ppm but make sure you set your Free Chlorine (FC) level to at least 4.5% of the CYA level so around 3-4 ppm. The higher CYA level should let you lower your SWG output as less chlorine will get broken down by the UV rays of sunlight. A lower SWG output means less aeration which means less of a tendency for pH to rise. You should also target a pH of around 7.7 instead of 7.5 unless you find it easy to keep the pH that low. If you have the CYA at 60-80, then your TA target should be at least 80 ppm if not 70 ppm. Your Calcium Hardness (CH) should be around 300 ppm. This will give you a saturation index of around -0.2 to -0.3 which should help. If necessary, you could go even lower in TA, but I don't think that will be necessary.


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