Question regarding D.E. as supplement

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L

Linkterfur

0
Feb 26, 2012
59
Stowe, VT
I wish to use some D.E. powder to supplement my sand filters. I have a couple of questions for ya'll.

1) Since I have two sand filters for the pool, does that mean I'll need to use twice as much to get the PSI to raise by 1? I ask this because usually the first filter in line gets dirty a lot sooner than the second. I'm worried that it's not going to distribute evenly and the first filter will raise by 1 and nothing on the second filter.

2) When should I stop using D.E.? I've read that you should replace it after every backwash, but will there be a point at which it's no longer as beneficial?

Thanks in advance, and sorry if this is not where I should have posted this
 
With two filters in series (one after the other) it makes sense that the first one would get dirtier. When you add DE, unless you can somehow direct it to the second filter only, then it will get caught in the first one and not make it to the second one. It doesn't make sense to have the first filter filtering smaller particles than the second one the second one will never have anything to filter and just ends up providing flow restriction/head loss.

If I were you I might switch the sand in the second filter to zeobrite or a similar substitute that claims to provide better filtration than sand.
 
I would suggest DE (if you want to use it) in the second filter only.....for the reasons carlscan26 indicates.

More and more, the forum is seeing problems with zeobrite. It's all anecdotal, but I have read enough I wouldn't use it in my pool. I have a sand filter that works fine without DE....just sand.
 
I agree that w/ two filters in series, one would want the finest filtration on the second unit. I'm not sure how that would work in practice, as to the method of loading it. Perhaps the first filter could be set to bypass, and then a couple of handsfull of DE could be added to the second filter.
DE fills in the spaces within the sand grains, to get filtration within the filter media, as it were. You only want to coat it enough to help trap finer particles, but not to clog up the filter w/ just DE, so you don't want to add more than a PSI or so of pressure to the filter.
 
carlscan26 said:
With two filters in series (one after the other) it makes sense that the first one would get dirtier. When you add DE, unless you can somehow direct it to the second filter only, then it will get caught in the first one and not make it to the second one. It doesn't make sense to have the first filter filtering smaller particles than the second one the second one will never have anything to filter and just ends up providing flow restriction/head loss.

If I were you I might switch the sand in the second filter to zeobrite or a similar substitute that claims to provide better filtration than sand.
Click to expand...

well... I wouldn't say that they are piped in series, or maybe I'm missunderstanding you as I'm comparing it to electricity. The water that flows through filter #1 does not flow through filter #2. I'll see if I have a picture I can upload so this can be confirmed.

I've heard that zeobrite only needs half the amount of sand that is necessary for a sand filter, yet is a finer filter. I don't plan on using it anytime soon, but you still need to meet the freeboard so you still use the same amount anyway, right?
 
photo.jpg




Sand Filter #1
photo-1.jpg





Sand Filter #2
photo-2.jpg


The 4" pipe is leads in from the pump, you can't really see it, but the green circle with "3" on it in the first picture on the very right is where the pump is.
 

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OK yes that looks like they are in parallel.

What does the pipe reduce to from the 4"?

Which set of exit lines from the filters are the returns and which are the backflush lines? Are the check valves on the output (return) side of the filters or are those on the backflush lines?

I'm curious why the first filter would get dirtier than the second one...it seems like the system should balance. It would be interesting to put flow meters on the return side of each of the filters to see if there is a difference between them.
 
I would figure that if one filter gets dirtier, it would only be temporary, and as it began to 'dirty-up', the other filter would take up more of the flow. Water, like electricity, will take the path of least resistance, so if one filter presents less of a restriction, it will flow more. In this regard, given equal media loads and equal piping loss, they should, at worst, oscillate with the least dirty filter flowing the most until it catches up in dirt-load.
 
carlscan26 said:
OK yes that looks like they are in parallel.

What does the pipe reduce to from the 4"?

Which set of exit lines from the filters are the returns and which are the backflush lines? Are the check valves on the output (return) side of the filters or are those on the backflush lines?

I'm curious why the first filter would get dirtier than the second one...it seems like the system should balance. It would be interesting to put flow meters on the return side of each of the filters to see if there is a difference between them.
Click to expand...

I believe they reduce down to 2", though it could be 1 1/2".

The "exit" line that is left of the multiport valve is the return, which flows into the heat exchanger, and the line on the right with the "sightglass" (which is not all that great) is the waste line. The line with the check valves is the waste line, the waste line is shared with the plumbing of the hot tub, which is way to the left. If I could convince them to buy 2 flow meters I would, that doesn't seem likely though.

I've only backwashed filter #2 (on the left) once in the last 3 months. But filter #1 about once a month.
 
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