Baking soda and calcium joined forces against me

[m100psi]

Hi all,

I have some new stains on the floor of the deep end of my pebble-tec pool. I thought they were created just because I waited a couple minutes before sweeping away the baking soda I had added before adding calcium chloride. But reading through other threads, I wonder now if I added the calcium before sweeping the baking soda, thinking I'd sweep them both at the same time. In any case, the marks are definitely only where the baking soda had collected before sweeping.

Are these stains calcium scaling? Is there any way to remove them without draining the pool? If I do need to drain the pool to remove them, how much should I dilute 31% MA in the solution I use to scrub them off?

Thanks,
Matt

 

[JoyfulNoise]

Unless your fill water is very soft (less than 50ppm CH) then there really isn’t a good reason to add calcium to your pool water. Most areas in the Western USA have hard water and so the pool water CH will rise over time.

But yes, adding calcium chloride and sodium bicarbonate together or within a day of one another is a bad idea. Both can rapidly sink towards the bottom of the pool and create scaling.

I advise you wait before doing anything drastic. If you keep you CSI negative (around -0.3 to -0.1) for a while the stains may slowly dissolve away. Acid etching plaster is a recipe for disaster and that would certain damage your plaster and make it look worse than the few stains you are seeing now.

 

[pjt]

the baking soda I had added

What's your TA?

In 12 years of pool ownership, I've never once needed to add baking soda.

 

[m100psi]

Unless your fill water is very soft (less than 50ppm CH) then there really isn’t a good reason to add calcium to your pool water. Most areas in the Western USA have hard water and so the pool water CH will rise over time.

But yes, adding calcium chloride and sodium bicarbonate together or within a day of one another is a bad idea. Both can rapidly sink towards the bottom of the pool and create scaling.

I advise you wait before doing anything drastic. If you keep you CSI negative (around -0.3 to -0.1) for a while the stains may slowly dissolve away. Acid etching plaster is a recipe for disaster and that would certain damage your plaster and make it look worse than the few stains you are seeing now.

Yes, I live in CA but the fill water in my city is very soft and I have to add calcium every few months to keep the hardness value up. I'll follow your advice and just keep the CSI slightly negative for now, which it generally is anyway.

Hopefully others see this and don't do what I did. If the pool school literature doesn't yet mention anything about adding baking soda and calcium on the same day, it would be a worthwhile addition. I saw you mentioned in another post CaCl2 should be dissolved in a bucket, then the solution poured in by a return. I'll definitely use that method going forward.

Thanks,
Matt

 

[m100psi]

What's your TA?

In 12 years of pool ownership, I've never once needed to add baking soda.

That's surprising, but I guess every pool is different. My TA decreases slowly over time. It was 50 when I added baking soda to get it back up to the middle of the ideal range.

Matt

 

[ajw22]

That's surprising, but I guess every pool is different. My TA decreases slowly over time. It was 50 when I added baking soda to get it back up to the middle of the ideal range.

Matt

A TA of 50 is fine. The middle of the ideal range is not more ideal then anywhere in the range.

A lower TA is better with a SWG. It keeps the CSI down and prevents scaling in the cell.

Let your TA find its equilibrium with the pH in your pool and don’t tinker with it.

TA - Further Reading

www.troublefreepool.com

 

[JoyfulNoise]

Something doesn’t add up here -

1. Your CH is decreasing all the time and you have to add it every few months even though you add municipal water which has calcium hardness in it;

2. Your TA is falling all the time even though you are not using any acidic forms of chlorine (you use an SWG which has no affect on TA).

Does your pool have a leak? Does it rain a lot where you are or do you use rain water to refill the pool? What is the TA and CH of your fill water?

The CH in your pool should never decrease on its own unless you have massive amounts of splash out. TA doesn’t decrease unless you add some form of acid regularly and the fill water is low enough in TA that it can’t keep up with acid additions.

 

[mknauss]

but the fill water in my city is very soft

Folsom Lake water. Appears to have a CH of around 40 ppm. But as Matt said, unless you are draining the pool often or have a leak, the CH should rise over time.

 

[Cena_sea]

I have a similar CH for fill and the calcium has also been dropping from initial plaster--have never added any calcium. I had a hard time being accurate with the test because it seemed to stay purplish no matter how many drops I put in, but I read somewhere on here to put in 1-2 extra blue drops and that has helped me a lot with seeing the color turn blue.

Edit: I didn't do start up so not sure what was added initially. Also I bought some calcium but now I'm thinking I should wait before putting any in.