DE in a sand filter???

[CarlD]

If your pool is clear, your FC and CC are fine, you don't keep having drastic chlorine drops, then the detritus in your filter is past rotting and you needn't worry about it.
Backwash when the pressure goes up. If it's once a week or once a month, so be it.

However, if you DO get an infested sand filter (very rare, but I know someone who had one) it's cheaper and easier to just replace the sand. At $5 for 50 # it's not pricey.

[The Raddish]

Here's a question. My new Pentair Dynamo 3/4 Hp two speed pump is being delivered today. I plan on running the pump on the low speed setting for about 12 hours a day (turning off at night), and only using the high speed setting for vacuuming, running the fountain when we have guests, and during high bather load.

So, if/when I add DE to the filter, do I add to 1lb increase on the low setting, or the high setting? I'm assuming that I add to a 1lb increase on the low setting, but wouldn't that equate to more than 1lb when it is on high?

[CarlD]

Absolutely add the DE when running on high. Do not do it on low. The pressure may well be too high if you add it on low.

I have a two speed and use the DE and always add it when the filter's on high--it's easy because I backwash on high and I add the DE right after I backwash.

[The Raddish]

Thanks Carl. That's the answer I was expecting.

[AndieP]

I went to Lowes today to get some DE for our filter and all they had was a 25pound bag....it was cheap $13... but now I'm wondering how well it keeps. Will it keep through the winter until next summer since I'm sure I won't use even 1/4 of it the rest of this summer? How should it be stored? Should I take it back and keep searching for a small size?

[drband]

Should keep indefinitely... just keep it dry so it won't clump up.

[gerri]

DE is actually little microscopic skeletons so it's good basically forever.

[brent.roberts]

If your pool is clear, your FC and CC are fine, you don't keep having drastic chlorine drops, then the detritus in your filter is past rotting and you needn't worry about it.
Backwash when the pressure goes up. If it's once a week or once a month, so be it.

However, if you DO get an infested sand filter (very rare, but I know someone who had one) it's cheaper and easier to just replace the sand. At $5 for 50 # it's not pricey.

Carl
I'm not sure the idea that the stuff in the filter is past rotting is valid. Last summer I got a new DE filter. The dealer did not supply the multiport valve so I could not backwash. The instructions, as usual said to backwash after noting a pressure rise. After 2 month my pressure only went up 1 1/2 lbs so according to the bood, it didn't need a backwash. But I decided to open it up and hose it off anyway.

I was astonished at the amount of cr@p on the DE. The smell was horrendous. The pool water still showed negligable CC and the FC was held pretty steady at about 5 PPM so it looked OK externally.
But inside YEAUKKKKK.

Next cycle I opened it up again after 1 month. Virutually the same mess. The chlorine does not really break down the stuff in the filter the way I expected it to. Now I clean the filter every two weeks. The blankety blank dealer still has not send the backwash vales so I still do it the hard way. But I won't every leave it for a month or two.

Try taking a 5 gallon pail and catch some of the backwash water about a minute after the flow is reversed. Pretty disgusting.

[waterbear]

Carl
I'm not sure the idea that the stuff in the filter is past rotting is valid. Last summer I got a new DE filter. The dealer did not supply the multiport valve so I could not backwash. The instructions, as usual said to backwash after noting a pressure rise. After 2 month my pressure only went up 1 1/2 lbs so according to the bood, it didn't need a backwash. But I decided to open it up and hose it off anyway.

I was astonished at the amount of cr@p on the DE. The smell was horrendous. The pool water still showed negligable CC and the FC was held pretty steady at about 5 PPM so it looked OK externally.
But inside YEAUKKKKK.

Next cycle I opened it up again after 1 month. Virutually the same mess. The chlorine does not really break down the stuff in the filter the way I expected it to. Now I clean the filter every two weeks. The blankety blank dealer still has not send the backwash vales so I still do it the hard way. But I won't every leave it for a month or two.

Try taking a 5 gallon pail and catch some of the backwash water about a minute after the flow is reversed. Pretty disgusting.

You are actually better off breaking the filter down instead of backwashing it. I have posted my reasoning for it in other threads so I will not go thru it again but in a nutshell you really don't know how much DE is washed out so you really don't know how much DE to add. Also, backwashing forces dirty water backwards through the grids. You know that if you run a DE filter, even for a short time, without DE the grids can get clogged. IMHO, the same can happen when the water goes through them backwards.