Calcium issues with patio and coping

[lburr]

I’ve researched the forums and know the advice is not to add calcium to a vinyl pool, but Im concerned about the brick coping, mortar, and concrete patio surrounding our pool. There are a lot of children swimming this summer and that means a lot of pool water leaves the pool. There is always some grit in the bottom of the pool after a swim day.

Our CH reading is 50. Tap water tested at CH 175 but almost all of our pool water is rainfall; we have to lower the water level due to heavy rain more frequently than we need to top it off with water from the hose. The CSI number is always lower the recommended number.
is there any reason not to add calcium? And if I do, what number CH should I aim for?

recent readings:
FC 3.5
CC .5
pH 7.5
CH 50
TA 60
CYA 30
CSI -1.0
water temp 85 F

Thanks for your input.

 

[mknauss]

You can add calcium if you like. Use Cal Hypo instead of liquid chlorine.

But as far as the pool water affecting the concrete not in direct connection with it, no. Does rain dissolve the brick coping, mortar, and concrete patio? Rain has 0 calcium in it.

 

[JoyfulNoise]

Agree with Marty. In climates/locations where pools are mostly vinyl, water is mostly acidic in nature, and significant rainfall happens, cal hypo is a very logical choice for getting chlorine into your pool. It will help support your CH levels and it’s way easier on your back to add a pound of cal hypo to the water than lug around an 8lbs jug of mostly water.

 

[lburr]

Thank you both for your feedback. I had had the same thought about Cal Hypo and had some left over from our first month with the local pool store. Used it a few times this month but not enough to budge the CH upward. it leads to another question— the Cal Hypo causes a residue on parts of the pool bottom that we find the following morning. It’s located along with the usual grit/debris but it is not something that ever appears with our usual application of liquid chlorine. It is a gray green filmy substance that is cleared up by the Polaris without any issue, but what is it? And is it telling me something about the pool chemistry that I need to understand? The darker blob in the photo is just a leaf.

The Cal Hypo is Pool Life Turboshock and label says it is 78%. Water is perfectly clear above that stuff on the bottom. This photo was from one morning after I applied about 12 oz cal hypo the night before, broadcast over deep end .

 

[mknauss]

When you brush that material, what does it do?

Appears like dead algae. Have you done a Overnight Chlorine Loss Test recently?

 

[lburr]

I don’t recall anything specific about brushing the residue or finding anything slimy in the Polaris net. I checked my log and see I did an OCLT on 7/14 and 15. Between 9 and 10 pm I tested FC and CC(5.5 FC/.5CC), added 12 oz Cal Hypo, retested (9FC/0CC), and tested at 6:30 am the next morning (8.5FC/.5CC).

 

[mknauss]

OK == keep an eye on it.

The cal hypo itself should not leave any residue.

 

[lburr]

Thank you. I have a large supply of bleach stockpiled and only a bit of Cal Hypo left, so it looks like I will stick with the bleach for now and only buy more Cal Hypo when needed. At least it is good to know that is a viable option as the bleach hasn’t been easy to find this season ( hence the large number of gallons in the garage).
Your help is much appreciated.