Is DE in a sand filter only a short term thing?

[Brett S]

So I recently had a bit of an algae issue and needed to SLAM my pool. During the SLAM the pool wound up blue and cloudy and I decided to add some DE to my sand filter to help the filter clear up the water. I bought some of the Chlorox DE media from Lowes and discovered that there are instructions on the box for using the DE media as a “sand filter booster.” In those instructions they suggest adding the DE media until the pressure is increased by 1lb, but then they say to back flush the sand filter and remove the DE media after 24 hours.

Is there any problem with leaving the DE media in the sand filter indefinitely? (At least until the pressure increases to 20% over normal and I would need to backflush anyway). I don’t believe that the TFP post on using DE media in a sand filter suggests that this would just be a short term thing.

 

[mknauss]

You can leave it until your filter pressure rises by the 20%. Typically that does not take long if you are clearing dead algae.

The DE just makes your sand filter 'dirty quicker'. A dirty sand filter 'filters' better than a clean one.

 

[Brett S]

Luckily the fact that the filter is oversized for my pool and the fact that the algae problem was caught before it got really bad has allowed my filter to eat all the dead algae with only a nearly imperceptible rise in pressure. I added the DE yesterday afternoon and the water this morning is the clearest I have ever seen my pool, so it definitely seems to be working.

Unfortunately I lost 3ppm of FC last night, so I haven’t passed the OCLT yet, but I’m hoping that will happen tonight.

This was the state of the pool when I started the SLAM on Friday. It wasn’t too terrible, but there was definitely a cloudy greenish tinge to the water.

 

[Brett S]

And here are a couple more pics. This was yesterday morning before I added the DE. It was blue again, but still a little cloudy



And here it is this morning. I’m not sure it can get any clearer. It’s a pretty overcast day today, but I feel like it would qualify as sparkly if the sun was out.

 

[mknauss]

Looks good. With a 3ppm FC loss over night it was still cleaning up something. I would give it a couple days at SLAM level.

 

[jtpipkin]

I've started keeping DE in my sand filter since I'd started a month or so ago. One word of caution, as Marty noted above, when there is something that needs to be cleared, keep an eye on your gauge. It will jump well over 20% quickly if there is something that needs to be caught... It will mean a pretty significant exchange of water too since that's the only way to drop the pressure again.

 

[spanman]

You can leave it until your filter pressure rises by the 20%...

Will back washing the sand filter remove the added DE? In other words, will new DE need to be added after each back wash?

 

[Brett S]

Will back washing the sand filter remove the added DE? In other words, will new DE need to be added after each back wash?

Yes, backwashing will remove it and new DE will need to be added. But that said, I got a 24 pound package of DE for about $23 from Lowes and only needed 3/4 of a cup for my 16” sand filter. I think this is pretty much a lifetime supply using only 3/4 of a cup at a time.