How much water do I need to drain to lower Calcium Hardness?

[doug527]

My CH is 350 400, I have roughly 19.5K gal. pool….How much do I need to drain to get CH to 200 or so?
My water coming out of hose is 100 ppm

Thanks

 

[Texas Splash]

Simple math via PoolMath, replace 50% water to cut it in half. So a CH of 400 w/ a 50% water exchange should get you to about 200.

 

[Texas Splash]

Keep in mind you are adding water with some calcium back in, so that may sway the result slightly upwards. Are you using a speedstir for your CH tests?

 

[mknauss]

A CH of 350 is great. Thats what mine starts at. Easily managed to 800+.

 

[doug527]

Im using a Taylor, strip and occasional water test from P&P. The reason I a want to lower is pool is new as of 5/2019. My finish is Stonescapes aqua blue, small pebble. I have places roughly palm sized that began to lighten in color and make stones less visible, as if stones are being buried….Stonescapes blamed my CH and said spots are calcium deposits…Ares Im speaking of are smoother than pool finish, not rough like a deposit would cause. I think it's BS myself but I want to get it down before I call the contractor to come look….Remind you these spots started first couple months and originally was told it was an effect called hydrating which no one has heard of….I think it poor craftsman ship myself..Below the line in first pic, second pic shows problem in circle but that areas around circle are effected also. This is on the steps where problem began

 

[mknauss]

CSI is what matters for scale formation. See CSI and LSI - Further Reading

 

[jseyfert3]

Simple math via PoolMath, replace 50% water to cut it in half. So a CH of 400 w/ a 50% water exchange should get you to about 200.

67% actually, per PoolMath. He stated his fill water is 100 ppm CH, and PoolMath lets you enter the fill CH to get the % replacement.