Adding DE to sand filter

[The Raddish]

#update-sticky

NOTE: I've moved this thread to this forum so that there is an easy access to adding DE to Sand filters. It's not a PERFECT thread on "how-to" but it will tell you how. I'm add these instructions at the top of the originating post by The Raddish.
CarlD, Moderator.

Here's how I do it:
1) Backwash your filter. Note the pressure it's running with.
2) mix about 1/3 of a cup of DE into a few gallons of pool water.
3) pour the mix slowly into your skimmer while the pump is running. If it's a 2-speed, use low speed.
4) WAIT about 20 minutes and see if the pressure rises. If it does you want it to rise about 1 lb.
5) If the pressure doesn't rise, or rises less than 1 lb, repeat steps 2), 3) and 4).
6) If the pressure has risen 1 lb, you are done. (frankly if it goes up 2 lbs, I'm OK with that. ) A 1 lb rise is your target.
7) If it goes up 5 lbs or more, backwash and start again, but use less DE.

That's it! Everytime you backwash you have to do this again, but once you know how much DE to use, you'll just add that much.

I hope this helps.

Carl


I keep reading about people adding DE to their sand filters to help with the really small particulates that accumulate into the pool. I've already started using a skimmer sock and that has helped tremendously, but I'm thinking maybe a bit of DE would help even more.

How to do you add it? Do I need to remove the multivalve from the filter (something I DON'T want to do), or can I just add some into the skimmer? If I have to remove the multivalve, I guess I'll just pass on the idea, as plumbing hassles will abound.

[CarlD]

Nah, it's a SNAP!

The ONLY thing you have to remove is the skimmer sock!

Start by recording your pump pressure.
Then add 1/3 cup into the skimmer (of course while the pump is on! ).
Wait 20 minutes and see if your pressure is up one pound.
If not, repeat: add another 1/3 cup and wait another 20 minutes.
When your pressure has increased one pound you are DONE! Just note how much DE you used (probably a cup or less).

When you backwash, you lose the DE and need to add the amount you figured out above--no need to struggle with checking it again and again.

If you put in too much, your filter will clog, suction will drop, and pressure will rise. Just backwash and you are back to square one!

It's as simple as falling off a log. I bought a 10# box late July early August and haven't even finished the FIRST 5# bag in it! So it's cheap, too!

[ScottS]

It's as simple as falling off a log. I bought a 10# box late July early August and haven't even finished the FIRST 5# bag in it! So it's cheap, too!

Carl where do you find such small bags of DE? I called most pool stores in my area and they all sell 20-25lb bags.

[CarlD]

Carl where do you find such small bags of DE? I called most pool stores in my area and they all sell 20-25lb bags.

A local pool dealer has them. Runs about $8-$9 a box so it's more expensive per pound than big boxes, but still cheap.

[The Raddish]

Okay, I have now added two cups of DE to my filter with no pressure change, and I'm not inclined to add more. Also, it appears that the DE is floating around in the pool now instead of in the filter, as I can definitely see much more particulate matter by way of the pool light than there has ever been before.

Will this stuff eventually filter out?

I removed my skimmer sock, and added 1/2 cup (couldn't find a 1/3 cup measuring cup) at a time to the skimmer, slowly. I waited about 30 minutes between each add with NO change in pressure.

Did I do something wrong?

[gordyjamz]

hey raddish, I posted a thread about three weeks ago concerning this. I ran into the same problem. I tried the trick and it didn't work. It caused my water to go cloudy. It seems to work for some, and not work for others. I think it depends on the filter. You should backwash immediatly if you feel its not working. It may take a few backwashes to get all the DE out, but once you do, run the filter 24/7 for a few days and it should clear up.

[KurtV]

Raddish, I'd open up the filter and check the condition of the sand. You may well have some chaneling that is allowing the DE through the sand.

Also, what size pump and filter do you have? What is the normal (freshly backwashed) pressure at the filter?

[The Raddish]

The pump is a brand new (less than a week old) Pentair Dynamo 3/4hp two speed pump. I added the DE while the pump was on the high speed setting, and left the pump on high for the 12 hours or so following the introduction of the DE. Even after the pump was set to low, there still remained a lot of particulate matter that could be seen in the pool light.

During the daytime, the pool water does look crystal clear. The only time I can see any particles in the water is when it flows past the light at night.

The filter is a new (installed in early June) Hayward 220T with new filter sand.

I had just backwashed prior to introducing the DE to the filter. The normal pump pressure is 9.5 psi on the high setting.

[CarlD]

Not sure what is going on...unless you don't have sufficient sand in your filter (must have at least 200#). It sounds like you may have a cracked lateral, or the sand isn't distributed correctly.

In any case, I don't think it's a DE problem but the DE blowing out is merely a symptom of a much deeper problem.

[The Raddish]

Okay, I decided not to backwash and let it go a couple of days to see what would happen, and last night I noticed that my water was clearer than it has ever been. There was virtually no particulate matter to be seen in front of the pool light!!

I guess the DE trick does work, and perhaps I just introduced it to the filter too fast or something. At any rate, next time I backwash I'll go a little slower with the DE and see how much I'll need to get the job done.