Understanding Calcium Hardness CH

[MHumphrey]

What exactly is the significance of Calcium Hardness (CH)? I understand it can manifest itself in either leaching calcium from a plaster pool (which i have) or leaving calcium deposits, but i'm not sure what affects it. Every time I do the CH test, it is the same - 450 or 475. I've been living in this house for about 9 months, and the pool was completely re-surfaced about a year ago. I've had to add in plenty of water (due to evaporation, and lettings some out for tile repair) over the past 9 months. Yet the results of the test are always the same.

Mostly, the number is not in the range that the "Pool Math" says it should be. Do I need to be concerned about it?

Thanks

 

[jblizzle]

The only way for the CH to go down is by removing water (not from evaporation) and adding water that has lower CH. In fact when the water evaporates it leaves the CH in the pool and then when you refill, you are adding more CH ... so usually the CH climbs due to evaporation unless you get a lot of rain and have to dump water which would lower the CH.

You CH is not terribly high and if you keep your pH in line < 7.8 you should be fine.

 

[Divin Dave]

Hi,
calcium in important in a plaster pool. Several things could happen if the chemistry gets out of whack.

If you have too much calcium in the water and your pH gets out of hand, the calcium can precipitate out of the water and attach itself to the plaster resulting in calcium scaling

on the flip side, if your calcium is too low, the water will leach calcium out of the plaster resulting in weakening the plaster and possibly pitting it.

your CH is not terrribly high, its easily manageable.

In all cases, pH plays a large role in whether or not the CH precipitates or leaches from the plaster. You need to be very diligent with keeping your pH within range. When you do not keep your pH within recommended levels, is when you realize problems with CH.