Calcium Hardness...What exactly is it?

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gobble9

Member
Mar 20, 2024
10
New Jersey
Hi TFP!

I have been following this forum for months since we opened our 34,000 plaster pool with spa, SWG. Amazing resource. I am very hands on, Ive learned a lot and look forward to learning more.

I do frequent the local pool store for a quick water test. And I am aware of these pool stores and their tests giving me their "numbers" and spectrums. I aim for the TFP numbers to achieve.

I noticed my Calcium Hardness number in the mid 300s last few tests. Pool store is telling me it's too high, need to sequester and/or drain water. Pool store wants the number between 100 and 200.

TFP numbers are telling me "ideal" Calcium to be at 350-500.

Between the two, it seems like a large disparity. Who is right?

What are the effects on plaster pool and equipment if Calcium is too high?
What are the effects on plaster pool and equipment if Calcium is too low?

Thanks - Christopher
 
They like to pull numbers out of the air, highlight them in total isolation and then swear they’re “too high” or “too low” … the correct follow up question is -

Too high or too low FOR WHAT REASON?

If you were to ask them that, you’d likely get some word-salad response about calcium, plaster, etching, porosity, corrosion, blah, blah, blah.

The articles linked to above lay out the principles involved - SATURATION BALANCE. Saturation balance involves many different water chemistry values (pH, TA, CH, salinity, temperature) and thus can be affected by one or all of those values. You are aiming for water that is BALANCED or very slightly UNDERSATURATED with calcium carbonate when dealing with a plaster pool surface. That water condition can be achieved by many different combinations of pH/TA/CH. As long as you manage the saturation balance of the water, the individual values don’t matter as much. Their combination is what is important.
 
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