the truth on DE filters

[Durk]

I bought a bag of Perlite (Brand name Aqua Perl) to try. It's slightly cheaper than DE per dose so I figured why not. Three years later, I'm still using it. I'm pretty dialed in on pool maintenance now, thanks to this forum, and I only backwash at close-of-season. I can't see any difference in performance to DE. That said, I have no idea how it would perform permanently, as I discard it after 6 months of use. I'll probably buy another bag in 2012; I should have one dose left out of the 12lb bag (gives 24 DE scoops--I use 6 at start-up).

Volcanic in origin, Aqua Perl is 100% crystalline silica free.

....in case somebody asks.

http://www.worldminerals.com/docs/aquaperl.pdf

 

[wetwilly]

Consider also that DE filters have grids that eventually wear out and they are not inexpensive. I'm not sure how long they're supposed to last.
I replaced one set after about 7 years. The grids get holes in them and leak DE. I got by for a while patching the holes with silicone but
eventually just replaced them.

 

[duraleigh]

My friend, Brice, is a filtration engineer with Pentair and, of course, they sell all three types. A comment he made has stuck with me over time. Ranked in order, DE filters filter the finest but cartridges are not so much in the middle as being much closer to sand. In other words, DE's filtration capability is much better than cartridges and cartridges are not that much better than sand.

HERE'S MY REAL POINT IN THE POST, HOWEVER..........

Proper water chemistry trumps everything. Living algae in a pool cannot be removed by filtration...period. All three types of filters are perfectly adequate for our needs and it is almost an exercise in futility to think you can get a filter that will allow you to be less diligent in maintaining a proper water balance.

water-clarity-and-showin-off-just-a-little-t23969.html?hilit=water clarity

 

[PanamEric]

Wow...thanks for all the input.

This forum is really great. Wish I had found it years ago.
That is a lot of information...

So to sum it up Cartridge VS DE.
Carts don't backwash but instead the cartridges are hosed down maybe every 6months if sized properly (thinking 400 to 500sf for my 25k). They eventually need be replaced but most likely not before 5 years and perhaps a few years longer?
DE on the other hand needs backwashing which flushes the medium but (again) if sized right (thinking 48 to 60sf) this only needs to be done maybe every 6months or so. Grids need to be replaced similarly to cartridges at comparable frequency.
The major difference is in the filtration size which is around 5microns for DE and 10-15 for carts.

Carts can be coated with DE (or perlite) to improve the mechanical filtration to around DE but will get close to that on their own as they load with dirt.
In order to eliminate the water loss from backwash DE needs to be coupled with a retention tank (~$300)
Purchase costs for both DE grids and Carts seem to be comparable?
Replacement Cartridges possibly a bit cheaper than replacement DE grids but still a few hundreds in both cases (for ~400sf cart ~60sf DE size).
Am I getting this right so far?

So that brings me to 2 last questions:
1-hydro is very expensive here and I would like to run as short as possible cycles to keep the water clean. I have a flow between 120-150gpm timed with a 5gl bucket (no flowmeter).
Can I achieve clean water with short (8hrs) cycles if I aim around 400sf cartridge? There are all kinds of claims on manufacturers web sites but I don't hold too much faith in them. Especially that for a few of them their numbers don't add up. (if you multiply the surface in sf by the listed gpm you often get different results than listed).
2- the original installation on my 2"pump was reduced to 1-1/2" (which I found somewhat silly). I have separate lines for skimmer and drain which I connected to a 2"T when I had to replumb for the new pump so now I am coming in 2" but the exit is still 1.5" as there is only one jet. I am thinking of correcting to 2" by adding a second 1.5" line returning to the pool. Is this making sense, (will I improve the flow by reducing restriction) or am I breaking my head for nothing?
Thank you for all the contributions. This was really helpful so far.
Eric

 

[PanamEric]

In reply to Dave,

My whole point in this exercise was to eliminate the backwash cycle of my sand filter.

I only have lived here for half a summer season but in that half season I found myself twice in a position where I had to backwash due to greatly reduced flow (barely noticeable jet) and water level was low. I only had bare minimum water for essentials so could not do the backwash because it would have brought me below the skimmer. First time I brought in a tanker ($300) second time I just let it go and got lucky with a good rain fall the following week.
Mind you this was before I found TFP and my maintenance was not quite up to par and also I have only recently identified some issues with my filter (missing 150lbs of sand)...
Is it possible that I could need to backwash as infrequently as DE or cartridge with 600lbs of fresh sand in my sand filter?
Because if a properly loaded filter gives me similar run times than carts or DE then I don't need to change anything. I can surely work out a backwash every 6 months.
At worst I could buy a 400g tank (~$150) and backwash in there, let the sediment settle at the bottom and re-dump in the pool...
Thanks
Eric