Partial draining of pool

[adamt]

So I need to drain 18% of my pool (3400 gallons) because my CH is too high.

How do I know when I've drained enough of the water? Or not enough? Right now, I'm just guessing that by the time it reaches the second step, it's good.

Any better way of telling?

Thanks

 

[bdavis466]

How high is your CH?

That really isn't that much water to drain and your CH will likely be right back where it was in no time at all.

 

[adamt]

It's at 425. I'm trying to get down to 350 and the pool calculator told me to replace 18%.

 

[bdavis466]

There is no need to drain your pool right now.

When you enter all of your testing numbers into Pool Math, scroll down to the bottom of the screen where you will see a CSI number. The calcite saturation index is a numerical value that will indicate how aggressive or oversaturated your water is in regards to calcium carbonate (the main ingredient in CH).

You should aim for a value of -0.1 to -0.3. So long as you keep your water in this range, scale will not be able to form and there isn't any risk of your water being too aggressive and damaging your plaster.

Several people have CH levels well above 1000 ppm and manage it just fine, myself included. Usually you would just compensate with a lower pH/TA.

 

[scomea]

Have you tested the CH of your pool fill water? My fill water in North Texas has 100 ppm of CH of which I was suprised. (Before TFP, I did a partial drain and refill without checking my fill water CH and like bdavis said, CH climbed up rather quickly. My CH is 425 now and with pool fill water being 100, to reduce to 350, PM says to drain 23%. If my pool fill CH was 0, then it would require only 18% water replacement.)