Ress. vs Comm. ???

[cruzmisl]

HI All,
I am buying a Pentair FNS plus DE filter and trying to determine flow rates. There are 2 flow rate slisted for the filter. One is under Ress and the other under Comm. Which one do I use to calculate for filter size? I am thinking Comm. My 3/4 Whisperflo will flow 70gpm so I am undecided if I should get the fns 36 which has a comm of 72gpm or the FNS 48 which flows 96gpm.

Any ideas?
Thanks,
Joe

[eljefe281]

I believe you should use "Res".

It stands for residential, as opposed to commercial.

It is my own personal opinion that you should find out what the end-of-curve flow is for your pump and then select a filter with a rating approximately equal to that flow.

That is an extremely conservative approach, but one that I think is wise.

Small pump, big filter.

[cruzmisl]

Well then if that's the case I can get away with a 36sq.ft FNS plus since ress flow is 90gpm and my 3/4hp pump will only flow 70gpm. Should be a good match??

[eljefe281]

It looks like the end-of-curve flow for a 3/4 HP WhisperFlo is about 95 gpm.

The 36 sqft would probably be OK, but I would buy one size up. I don't know what the cost difference is.

That's just me.

[Poolsean]

DE filter flow rates are usually double the rated square footage of the filter. A 36 sq ft will have a max flow rating of 72 gpm.

[cruzmisl]

Well for the $100 difference in price I'll up to the 48 sq.ft model. Not worth the headache or aggravation if the 36 is too small.

Thanks!
Joe

[Poolsean]

ALWAYS better to oversize your filter.

[waterbear]

If you size closer to the commercial rate instead of the residential rate you will get a much longer filter run time (time between cleanings).

[waterbear]

If you size closer to the commercial rate instead of the residential rate you will get a much longer filter run time (time between cleanings) because this will oversize the filter in a residential application. You also have to take into account the addtional cost for the larger filter, however.