Filter replacement

chorchieAugust 22, 2011

Hi all,

I am hoping someone can shed some light on this for me. I am having a filter replaced and am trying to figure out which would be best given my set-up.

I have an kidney shaped oval in-ground plaster pool, approximately 17,000 gallons with an attached hot tub. Deep end is about 8.5', shallow is about 3.5 feet. One skimmer in the deep end, one drain in the deep end and one drain in the hot tub. I am not sure if the plumbing is 1.5" or 2" but can check that tonight.

I currently have a Pentair 1hp pump, a Pentair SMBW2000 series (36 sq.ft) and a very very old heater.

I know the filter is too small for the pool, so whichever filter I go with, I will go with nothing smaller than a 60. Currently, my filter normally operates (totally clean) at anywhere between 23-27 psi and after normal use jumps to around 30 or so. One shop said this is normal for that filter, but that, along with frequent cleaning, tells me that it is undersized.

A while ago, the filter started leaking from the bottom. We replaced the backwash valve but it continues to leak. I have a home warranty who has agreed to replace the filter.

So the real question is what to go with? I do my own maintenance, and am used to working with DE. I do like how well the DE cleans, but am open to all suggestions. I do hear that the DE is cheaper to operate since the cartridge filters need to be replaced every season or two.

I am considering the following:

Pentair FNS Plus with multiport valve

Pentair FNS Plus with push/pull valve

Pentair SMBW4060

Pentair Quad

Pentair Clean n Clear

Any suggestions would be greatly appreciated!

Thank you,


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I suspect the grid network is what caused your rapid pressure rise, not that it was undersized.

In addition to an annual tear down for cleaning, the grids also need degreasing. I suspect no one told you. The result was the fabric of the grids getting stretched. This cuts a grids usable filter area by more than 1/2, causing the rapid pressure rises and creating the leaking bottom.

A new FNS48 Plus will likely be more than adequate. The 60 would have a tough time backwashing well.

Given the age of the pool and the size of the pump, I would bet you have 1.5" plumbing.

When you change the filter, I would bet that you would see a pressure drop to about 16 PSI. I doubt, with a clean and properly balanced pool, you would need to back wash more than once in 3 months.


    Bookmark   August 22, 2011 at 7:20PM
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Hi Scott,
Thank you for the info. Would you recommend sticking with DE and going with the FNS Plus vs the SMBW? Would you prefer DE over cartridge?

Also if you still prefer the FNS, would you recommend the push valve or multiport?

Lastly, would going to a 60 (and what you said regarding backwash) be problematic? I would hate to undersize it, but it sounds like oversizing it could be a problem as well. I just don't want to get everything in and then wish I had gone larger. But don't want to go to large then realize I have problems because of it.

Sorry for the many and possibly redundant questions. This is my first time dealing with these questions and want to make sure I have thought of everything necessary.

Thank you,

    Bookmark   August 22, 2011 at 7:46PM
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If your OK with the tear down a DE filter need periodically, the FNS48 with an MPV is great.

I am not a big fan of the SMBW.

If you want DE clarity but the convenience of a cartridge, the Quad 80 with no MPV. Put a 3 way valve on the pump exhaust though so you can lower the water or vacuum to waste. With this combo, I seriously doubt you'd have to clean the cartridges more than twice a year. They just get hosed off and an annual TSP or powder dishwasher detergent soak to degrease them.


    Bookmark   August 22, 2011 at 10:15PM
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