Calcium Hardness

skyfly27

Member
Apr 5, 2021
19
Springfield Missouri
Pool Size
18000
Surface
Plaster
Can someone tell me why calcium hardness is important for a gunite pool? I measured mine at 150. The pool math calculator says I need to add 25 lbs of calcium chloride. Just wondering why this is necessary?
 

Texas Splash

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Jun 22, 2014
31,434
Texas, San Antonio/Marion, South-Central Area
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When the CH level gets too low in a a plaster pool, the water is starved for calcium and looks for a place to grab it - the pool shell. Over time that can result in plaster etching and damage. For that reason, it's important to have the minimum amount required. By contrast, if you had too much calcium and it over-saturates the water, it looks for a place to stick - scale.

 

skyfly27

Member
Apr 5, 2021
19
Springfield Missouri
Pool Size
18000
Surface
Plaster
When the CH level gets too low in a a plaster pool, the water is starved for calcium and looks for a place to grab it - the pool shell. Over time that can result in plaster etching and damage. For that reason, it's important to have the minimum amount required. By contrast, if you had too much calcium and it over-saturates the water, it looks for a place to stick - scale.

Thank you! Is there a more specific range? I am seeing 350-550
 

Texas Splash

Mod Squad
TFP Expert
LifeTime Supporter
Jun 22, 2014
31,434
Texas, San Antonio/Marion, South-Central Area
Pool Size
17888
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
CircuPool RJ-45 Plus
350-550 is about it, The range for CH gives owners plenty of flexibility to keep the plaster safe while preventing scale. Keep in mind a lot has to do the 3 other factors: water temp, TA, and pH ... pH having the biggest influence. But if you keep all your numbers within those recommended ranges, you'll be fine. Plus, the PoolMath APP will let you know if any area should be addressed, so if you have a questions if that happens just let us know.
 
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