Where to buy DE?

[waterbear]

Pool filter DE is different than food grade or gardening DE.

DE for pools comes in as small as a 10 lb box for around $10 (CURRENT PRICE BTW). I know becaue I used to sell it. Most people don't buy the small ones so many stores do not stock them.

If you have an ace hardware near you check them out if they sell pool chemicals and carry HTH, many bigger Ace do. They should have it in smaller boxes.

You can also order it online from several retailers including Ace. Just google HTH diamtomaceous earth.

As far as how much to add, it is generally between 1/2 to 2 cups (enough to raise the pressure by 1 psi and not more). You just don't want to add more than 1/3-1/2 cup at a time in a slurry through the skimmer when you are trying to see how much YOUR filter needs for the 1 psi pressure rise since it is easy to overshoot.

Since it does not go bad and you will need to add it with each backwash one box will last you that long time so even if you need to buy the bigger box it will get used up in time.