Newbie filter question


LifeTime Supporter
Aug 3, 2007
Athens, AL
First let me say that my water is still clear and sparkling because of my test kit....keeping proper chlorine levels in accordance with the chlorine/CYA chart.

I have a Hayward 300# sand filter. I dont have the particulars yet. What is the purpose of backwashing and how do I do this. Also when at the pool store for my first water test (before my test kit) the guy asked about my runs at a constant 20psi and drops to zero when I turn it off. What pressure should it be and when and what is involved with a sand change, if that is necessary.

Thanks In Advance


Mod Squad
TFP Expert
Apr 4, 2007
SW Indiana
Backwashing reverses the flow through the filter to clean the sand. You do it when there is a rise of 8 lbs or so in your pressure reading. Shut the pump off before moving the handle on the filter. Set the filter to backwash, and run the pump for a couple of minutes. Shut the pump off, switch the filter to rinse, and run for a minute or so. Shut the pump off and return to filter. Water will leave the pool through the waste line or backwash hose during backwashing and rinsing.

The normal pressure depends on your particular pool, filter and pump. 20lbs is higher than many pools, but nothing to be concerned about. If I were you, I'd backwash and then see what the pressure is and treat that as your normal pressure.

You'll probably never need to change the sand unless you have too much money and can't think of anything else to spend it on.