Calcium Hardness dropping constantly

NParker · May 6, 2015

Hello everyone!
I am a lead lifeguard at a pool I work at and I am having problems with our hot tub. We are adding in lots of calcium chloride to raise the calcium hardness and it is not doing anything. Our target is to get the CH up to 600 ppm and we have only been able to get it up to a 150 at most. We added 700 lbs. of CC to the spa throughout the month of April and it consistently drops. The spa chemicals other than that are pretty stable.
Chlorine: 2.0-4.0
pH: 7.4-.7.6
ALK: 80
The spa is an indoor spa that autofills; vinyl lined. The spa holds 3,675 gallons of water.
Does anyone have an idea of what the issue might be? I would be very grateful.

jblizzle · May 6, 2015

Welcome to TFP!!

Why would you want the CH that high? That is likely to only lead to further problems.

The only way for the CH to drop is by replacing water with a lower CH content. Are you sure the spa is not leaking and being refilled by the auto-fill?

umpalumpajay · May 6, 2015

From everything i've read on this site, CH isn't necessary in a vinyl lined pool. is there a reason you're aiming that high?
CH - Calcium Hardness
From Pool School:
"Calcium hardness indicates the amount of calcium in the water. Over time, water with low calcium levels will tend to dissolve calcium out of plaster, pebble, tile, stone, concrete, and to some extent fiberglass surfaces. You can prevent this from happening by keeping the water saturated with calcium. In a vinyl liner pool there is no need for calcium, though high levels can still cause problems. A plaster pool should have CH levels between 250 and 350 if possible. Calcium helps fiberglass pools resist staining and cobalt spotting. If you have a spa you might want to keep CH at at least 100 to 150 to reduce foaming."

duraleigh · May 6, 2015

Welcome to the forum. :wave:

Repeating what has been said, You don't need CH high at all.

The source of your issue is likely the autofill is satisfying a leak or a heck of a lot of splashout. What is the CH of your fill water?

YippeeSkippy · May 6, 2015

Very soft water here, about 40ppm CH

Can you turn the autofill off and watch for a drop in water level to determine if there is a leak?

NParker · May 7, 2015

The autofill water CH is at a 20. To answer every one else's question, because our boss from Atlanta HQ told us to raise it to that level. I did turn off the auto fill and the spa water is dropping fast around an inch every 5 minutes so I do believe that there is a leak somewhere in a pipe that I cannot get to.

jblizzle · May 7, 2015

There you go. That is quite the leak and that is why you can not raise the CH (to the ridiculous level your boss is asking for).