Calcium Carbonate Flakes?

[tkalla2000]

I have a SWG pool that gets small white flakes in the bottom of the attached spa. Most of the return water is sent to the spa and I only notice the flakes comming out when the generator is gererating. The SI was out of wack at first but I have got the chemistry correct and still have the white flakes.

FC = 5.0

PH = 7.6

CH = 350

TA = 90

CYA = 80

TEMP = 92

[chem geek]

The pH at the hydrogen generation plate is high so calcium carbonate flaking is still possible. You could lower the TA to around 75 ppm and you could also use 50 ppm Borates in the pool which acts as a pH buffer (it's also a mild algaecide). You can read more about adding borates here.

[quantumchromodynamics]

Start keeping your pH at about 7.3. This will cause your alkalinity to start to drop to the 75 that Richard mentioned. You can also add a stain and scale control chemical to help prevent the scale.

1) How did your calcium hardness get so high?

2) Is your heater before the salt cell?

3) Does the flaking increase when the heater is on?

[tkalla2000]

The Cell is before the heater, and the CH = is about 350 at the water fill.

Thank you Chem Geek, I will try to lower the TA a little more. I have herd Borates are bad for dogs and this guy has a dog that is around the pool allot. I don't know if the dog drinks from the pool, but I would not want to chance Borates if it could make his dog sick.

[chem geek]

You are right that if the dog drinks cups of water from the pool every day, then 50 ppm Borates gets closer to the first symptoms limit for male dogs which can result in smaller testicles (the highest No Observed Advere Effect Level, NOAEL, which is 8.8 mg/kg of body weight so for a 10 kg dog this is 1.76 liters).

[quantumchromodynamics]

I recommend that you begin to take the necessary steps to reduce your calcium levels to below 270 ppm. The easiest step would be to use softened water as fill from now on.

Having your salt cell before the heater is not a good idea. The chlorine going through the metal heat exchanger will corrode the metal. If possible, you should run them in parallel to avoid conflict.

There is also a small risk of hydrogen accumulating in the heater and causing problems. The salt cell generates hydrogen gas that usually harmlessly comes out of your returns and into the atmosphere. It is best to avoid any pockets where hydrogen could accumulate. Especially anywhere that contains fire, like a heater.

[tkalla2000]

Thank you all for the help. I will try to get the calcium lower and let you know if it worked.

[tkalla2000]

Got the CH down to about 250ppm, TA creeps up to about 120 from 80 every week. The flakes are still forming. I think the water temp is to high. The pools in my area are running about 86F at night and up to 97 during the day. If I drastically lower the TA to around 30 will this be hard on the plaster or equipment? I have tried to keep the TA at 80 but it still rises to 120 after 7 days, and the PH gets to 8.0.

[quantumchromodynamics]

You have to test the pH and alkalinity every day and keep them in line. You cannot allow them to go so high. Add acid every day if you have to.

You can't lower the alkalinity to 30; you have to keep the Saturation index from going negative or you will destroy your plaster.

Try to keep your S.I at zero. You probably have a lot of calcium carbonate scale that will neutralize any acid that you add for a while. Keep adding the acid until your pH stabilizes.

Can you test your fill water and post the numbers? How much fill water do you add every week?

[billp]

I have a SWG pool that gets small white flakes in the bottom of the attached spa. Most of the return water is sent to the spa... The Cell is before the heater...

The cell should be installed after the heater. If you have sufficient flow to operate both the heater and the cell they can be installed in parallel. The typical circulation pattern is to have most of the water return to the pool with a small amount returning to the spa to keep it fresh. (When most water returns to the spa you typically, but not always, have poor pool circulation.) If the cell is installed before the pool-spa diverter valve you will typically get white flakes in the spa. Most systems are now "self-cleaning" which means the polarity switches every so often to kick calcium deposits off the plates. These flakes go wherever the water goes. In my high hardness area most pools have moderate to high calcium which means there are white flakes appearing. The way to keep them out of the spa is to have the spa bypass line tee off before the cell. The flakes all go to the pool where they get vacuumed out. Sometimes they land on steps too. If you can follow the other advice and keep calcium low that is best, but if not some replumbing may be needed.