Need advice regarding cartridge filter...

[otisdog]

I've spent the last three years (yes, that's THREE) rebuilding my existing pool that was originally built in the mid 50's.

Lots of problems, lots of solutions, lots of money. The person who is setting up the electrical/control side of the equipment is a Pentair factory rep. He says that to take advantage of my variable speed pump(s), that I need to go with the "Quad" cartridge filter. He says that a non-cartridge filter has 12 to 15 more 90 degree bend in the interior of the filter.

The additional 1080 to 1350 degrees of bends in the filter puts more resistance on the pump, making the speed it has to run higher, cancelling the benefits of the variable speed. The town I live in requires that the filter be hard plumbed to the sewer line with a p-trap.

Someone told me that the quad filter can be backwashed, but that the plumbing for it is "backwards." Thoughts?

[PoolDoc]

Your Pentair rep is full of it. I'll let you work out for yourself what he's full of.

Pressure drops across various filter types (sand, cartridge, DE) are comparable.

Cartridge filters cannot be backwashed; they can only be washed manually after extraction.

I hope your buddy knows more about controls and wiring than he does about plumbing!

[otisdog]

I quote from the Pentair Quad D.E. brochure..."And cleaning couldn't be easier. In fact, you have three options...backwash and recharge like a traditional D.E. filter, remove and rinse off the cartridges, or simply remove the lid, leave the cartridges in place, open the drain plug and rinse."

[mas985]

A cartridge filter has the lowest head loss of any type of filter. The main reason is that it does not have a backwash valve which tends to have a lot of head loss. You can look it up in the manuals yourself. But here is a table I put together that compares the head loss through several filters +backwash valves:

https://dxodqa.bn1304.livefilestore.com/y2pY-hTapufMC1yrHcczMTXECzbk8ujb-agguxZ9Ecoav-usB7003_zT_2PRRsL9323I7AJgV9beY8mgGyQxG-I9QolH2YecBOrHWRNn3BL4jo/FilterTypes.jpg?psid=1

[PoolDoc]

From PacFab engineering bulletins I received in the early 90's:

https://lh4.googleusercontent.com/-W4w3CiubD3M/U4YmuaEE7sI/AAAAAAAAHF0/gBPO55CHPNE/s836/cartridge%2520filters.jpg

https://lh3.googleusercontent.com/-NetZGRkCzTA/U4YmvkdeXGI/AAAAAAAAHGE/EI25fPntXZU/s815/tr-filters.jpg

https://lh6.googleusercontent.com/-4Qk9YgcNcfQ/U4YmuW_O_wI/AAAAAAAAHF4/EIoxZO6ea_4/s824/DE%2520filters.jpg

https://lh5.googleusercontent.com/-X6hTOth_Kak/U4YmvmCUtZI/AAAAAAAAHGI/kC4kj5ZIBwE/s827/multiport%2520valves.jpg

When I was running flows over 60 GPM, I always switched to the PacFab Full Flo valve, now called the "High Flow Valve":
http://www.pentairpool.com/products/valves-hi-flow-valve-68.htm

Over a 100 GPM, I made backwash valve chains, using an H-ladder and 4 full port ball valves.

It's also worth noting that neither sand nor DE filters have a failure mode that approximates cartridge pleat collapse, illustrated on a System3 cartridge:

https://lh3.googleusercontent.com/-M_DScE6G5-g/UxZfjfrbkqI/AAAAAAAAGXk/Dxce8GBWqOg/s800/IMGP0725.jpg

(This cartridge also shows the effects of cleaning with a low power electric pressure washer. The pleat collapse results from high pressure drop across the cartridge that results when the filter clogs with algae or dirt. The 'fuzzy' fibers are a result of the pressure washing.)

Once that failure mode has been achieved -- and I've seen it on EVERY modern "high capacity" cartridge that's been used even briefly on dirty pool water -- the cartridge cannot be restored, and pressure drops are far greater than with the new, un-collapsed, cartridge.

[mas985]

The cartridges I was quoting were the Hayward SwimClear and the Pentair Clean & Clear plus. You can see the curves here:

http://www.hayward-pool.com/pdf/manuals/SwimClear-Cxx25-C7000.pdf
http://www.pentairpool.com/pdfs/CleanandClearOM.pdf

But this cartridge has even lower head loss:
http://www.pentairpool.com/pdfs/cleanclearrpOM.pdf

But you are right, there are some lines that are worse. I would never recommend those since they are usually pretty small.

As for cleaning a cartridge, I would never use a pressure washer. I use a small nozzle on the end of the hose which doesn't damage the fabric. That is probably one of the reasons why my cartridges have lasted so long (> 8 years).

[PoolDoc]

I think it's pretty clear that there are some serious weaknesses in specific models of filters within each filter group . . . and that information about these problems is hard for new pool buyers to acquire. It's something I'd like to work on, hopefully with your help.

Sorting out the whole problem with configuring and servicing electronic controls is out of my reach, at least for now. But I think we could do something useful with filters and pumps, that would help people make better decisions, and have better experiences with their pools.

[Pappy]

I quote from the Pentair Quad D.E. brochure..."And cleaning couldn't be easier. In fact, you have three options...backwash and recharge like a traditional D.E. filter, remove and rinse off the cartridges, or simply remove the lid, leave the cartridges in place, open the drain plug and rinse."

D.E. filter does not equal CARTRIDGE filter. Is this what your guy is suggesting?
http://www.pentairpool.com/products/filters-de-quad-de-cartridge-style-filters-139.htm

[Pappy]

The Pentair brochure seems a little misleading to me. I do see that it says a cartridge type filter, and in this case the "cartridge" is a removable D.E. membrane, but generally speaking a cartridge filter is a paper or cloth filter element. That is what I was trying to clarify. I very strongly suspect you'll NEVER pay for the difference in price of that filter and a good sand filter through the savings on electrical power.

[mas985]

Oh, Mark...? You've had a cartridge filter for 8+ years? You must have been a pioneer of sorts!
Not really. They were pretty common in our area when I installed it and with the drought restriction we now have, I am glad I have one.