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Thread: Filter Sizing?

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    Filter Sizing?

    I have a 48 sq ft Hayward Micro-clear DE filter and I'm tired of the maintenance. i was going to a Sand filter, but I like the No Backwash feature of a Cartridge filter. The Pool came with the house. It had a cartridge filter then, but it must have been too small. I had to clean it often and the replacement was >$100, then. I have a 34' x 16' Vinyl pool with a 9' deep end and diving board. 22,500 - 24,000 gallons, I estimate. Still using Chlorine sanitizer, but looking to change over to Salt or the Trouble Free method. I have a 1 1/2 HP Hayward Super II pump and 1 1/2" piping, maybe 2", not sure. One skimmer, two outlets and No Floor Drain. I have a Polaris with booster pump. What size cartridge filter do I need? When I bought the DE filter 10 years ago, I over-sized it a bit, from the recommendation. I'm in Atlanta, GA, moderate to low use. Lots of pollen in the spring and some trees, but nothing hanging over the pool. I have a yellow lab who swims often, so lots of hair. I'm tired of back-washing! What do you suggest? Thanks, Joe
    34' x 16' Vinyl pool with diving board and slide.

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    Mod Squad jblizzle's Avatar
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    Re: Filter Sizing?

    You really can not go too big on a cartridge filter ... just will cost more money up front and for filter replacement. The bigger it is, the less often you will have to clean it. Realize that clearing a green algae filled pool is a real pain with cartridge filters, so you want to stay on top of the chemistry.

    For your size pool, a general recommendation would be around 350sqft.

    As a note, your DE filter was not really oversized. We would recommend at least a 60 sqft filter to reduce the amount of backwashing required.

    EDIT: For completeness, the recommended sand filter size would be around 4+ sqft
    Jason, TFP Moderator
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    Re: Filter Sizing?

    I'm new to the forum but IMO. your best and least expensive way to go is to do the backwash thing.
    I wait until the pressure rises 10 (sometimes 15) psi above a clean powder coat before back-washing.
    DE is the best and least expensive way to keep your pool sparkling clean.

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    Melt In The Sun's Avatar
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    Re: Filter Sizing?

    If ease of maintenance is your #1 priority, get a big sand filter. You'll still have to backwash, but no adding DE afterwards. Cleaning the 4 cartridges will get old real quick, if you really have a lot of pollen and dog hair.
    11,200 gal, Pebble-Tec; Tristar 2-speed 1hp - Swimclear 325 ft2 cart - SWG - A & A in-floor cleaner - Heat pump. For the poolside cooking, a Yoder Wichita and a Big Steel Keg!
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    Re: Filter Sizing?

    Quote Originally Posted by lorenww
    DE is the best and least expensive way to keep your pool sparkling clean.
    Sand is cheaper.
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    Mod Squad jblizzle's Avatar
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    Re: Filter Sizing?

    Quote Originally Posted by lorenww
    I'm new to the forum but IMO. your best and least expensive way to go is to do the backwash thing.
    I wait until the pressure rises 10 (sometimes 15) psi above a clean powder coat before back-washing.
    DE is the best and least expensive way to keep your pool sparkling clean.
    Also want to point out that our recommendation is to clean the filter (any type) when the pressure goes up 20-25% of the clean pressure. Waiting for a 10-15psi rise will result in drastically reduced water flow rate and actually lowered filtering capability.
    Jason, TFP Moderator
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    Re: Filter Sizing?

    Quote Originally Posted by jblizzle
    Quote Originally Posted by lorenww
    I'm new to the forum but IMO. your best and least expensive way to go is to do the backwash thing.
    I wait until the pressure rises 10 (sometimes 15) psi above a clean powder coat before back-washing.
    DE is the best and least expensive way to keep your pool sparkling clean.
    Also want to point out that our recommendation is to clean the filter (any type) when the pressure goes up 20-25% of the clean pressure. Waiting for a 10-15psi rise will result in drastically reduced water flow rate and actually lowered filtering capability.
    Right...everyone's normal PSI will vary and in my case a 15 psi increase would be double my normal PSI of 15
    24'x52" AGP (13,500 Gallons), Intex SWG, (2)Solar Bear 4x20 panels, Hayward S220T Filter, 1/2hp Pentair Superflo

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    Re: Filter Sizing?

    ONe pool man's opinion:
    I would go with sand filter for ease of maintenance. If you are woried about the size of the particles it can filter use Zeobrite instead of sand. It will filter pretty much the same size particles as a DE filter but you will have to backwash more often. The filter I like the most is the Zodiac JS 100 Sand Filter. It is a beaty of a sand filter and very sturdy.

    On my pool I have a Zodiac CV 580 SQ Ft Cartridge Filter. Change out the cartridges every two years and you won't have a problem. Just buy new cartridges online for cheaper than most of us pool guys can get it for.

    Good Luck!

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    bobodaclown's Avatar
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    Re: Filter Sizing?

    I'm partial to cartridge filters. Get the largest you can afford. When you back wash you also drain out chemicals you've added and will need to add back in. I've got a SWCG and need to keep my TA in the 70's my fill water has TA in the 120's, so adding water I take a double whammy.
    17K Kidney Shaped Pool Concrete (Diamond Bright) Pool, 3/4 hp 2 speed 115V Sta-rite Duraglas PEA5D-180L/P2R5D-181L (Impeller C105-92PS Diffuser C1-216P), 1.5 piping, Pentair CC100 Filter , Heat Siphon 100K BTU Heat Pump Pool Heater, Flow meter Blue White Flowmeter Model No. F-30150P, Hayward Astrolight SP0581N, SWCG CalimarTitanium Edition TE45 , Dolphin Nautilus Plus with CleverClean, Lakeland Florida

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    Re: Filter Sizing?

    Quote Originally Posted by bobodaclown
    I'm partial to cartridge filters.
    Me Too!

    I am going on over 7 years with my current set of cartridges and they are still going strong. The life of the cartridge is largely dependent on the size. Larger filters are cleaned less often and have less flow rate per sq-ft of cartridge so they tend not to get damaged as quickly. I clean mine only once per year which I think helps extend the life of the cartridge. If I had to do it all over again, I would choose a cartridge.

    But one thing I don't think has been mentioned is local ordinances. Some cities require separation tanks for Sand and DE filters so IMHO it really doesn't make sense to go with anything other than a cartridge for those areas.
    Mark
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    Re: Filter Sizing?

    Good information, everyone. While each type and have experience with each, has it's own qualities, DE has become a real pain to maintain, and the grids are expensive. The pool, I now realize, came with a small cartridge filter, too small. I don't do underwater photography, so the ultra clear, polished water effect isn't that high on the list, though the sparkle it gives is nice. My pump equipment is in my Garage. I had a nice storm drain just outside the door and had the backwash pipe in it. Backwashing was a breeze. Cleaning the DE Filter was still a pain. The drive way contractor pushed concrete down the drain, even after pleading for him not to do that. It drains still, but not fast enough to take the load of backwashing. Now I have to roll out the hose and blow all of that nasty DE down the driveway. Sand would be a bit easier, but not too much. That's why I'm considering the cartridge filters, but they are so danged expensive to get a big one. Gotta bite the bullet some where. As to the pressure, 25% increase of clean pressure is nothing. I'm at 5 psi clean, that means a 1.25 psi increase, or 6.25 psi to backwash? I'd be baskwashing once a week! Sounding a little more like putting new grids in the old DE tank is looking better and better. I'd shoot the Driveway contractor, but he's bankrupt and probably working under a different name somewhere in one of your states, now. That drain pipe is 100' long, 6" corrugated plastic and goes under flower beds, the patio, lawn sprinklers and the middle of the back yard. Too bad it wasn't smooth bore PVC! Anyway, thanks, guys. Good info. I'll start looking for some bargains or a used one from someone like myself you wants to fill their pool in. It cost as much to do that as it does to build one, almost. I've checked. I consider all options. Happy swimming!
    34' x 16' Vinyl pool with diving board and slide.

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    Mod Squad jblizzle's Avatar
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    Re: Filter Sizing?

    That is a very low pressure reading from your filter. Do you have a very small pump or run it on a low speed? Does it go to zero when off? ... just seems odd.

    As I said before, your DE is actually smaller than we would recommend.

    My pool is under 20k and I have the 60sqft Hayward DE. My pressure has barely risen from 12psi in months ... after installing all new grids. Btw, pretty sure I got all 8 grids for around $130 ... which is not you too bad if you only have to do it every 5-10 years. I got the house used, so I did not know the history, but they were are smashed up and starting to leak ... Likely from lack of care.

    Posted from my Droid with Tapatalk ... sorry if my response is short
    Jason, TFP Moderator
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    Re: Filter Sizing?

    jblizzle, Jason, I wasn't sure if you were responding to my comment about the pressure or the comment earlier in the string about the pressure. I have a 1 1/2 HP relatively new, Hayrward Supper II pump. Don't remember the specs. but I was told a 1 HP was adequate, but since my equipment is in my garage and sits about 4' above the water level and about 20' from the pool, I sized it up a bit. I get about 5 psi after backwashing. If I take the grids out, which is a real pain, and thoroughly clean it, it may drop to about 4 psi. I have been backwashing when the pressure goes up by 10 psi, or around 15 psi, but I admit I have let it get a bit higher from time to time. The comment about backwashing when there is a 25% increase in pressure from the Clean pressure reading, was what I didn't understand. 10 psi is a 200% increase in pressure, and some people recommended a 15 psi differential. I think I'm sticking with my DE filter. Wish I had gotten the larger one to begin with. That makes perfect sense now. I was afraid, and possibly was told, that over-sizing the filter would cause me problems. I don't remember now. I inherited the pool as well, and very susceptible to bad advice. It had a 100 sq ft cartridge filter then and that was a real pain, but I've had, supposedly, knowledgeable people tell me for my pool that s/b be fine. Live and Learn, huh? I appreciate all of the advice. I'm looking at a set of Pleatco grids, any comments on those. They are about $106 on eBay, the Hayward's are about $130. Thanks, Joe
    34' x 16' Vinyl pool with diving board and slide.

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    Mod Squad jblizzle's Avatar
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    Re: Filter Sizing?

    Yeah I was responding to you about the pressure. And the 10psi (15psi) pressure rise before cleaning is just outdated and not a very good recommendation. You are right 10psi raise over 5psi is a 200% increase, while a 10 psi raise over a clean 20psi is a 50% increase ... this is exactly why a set increment does not make sense and using a % increase is applicable independant of your starting pressure.

    The 20-25% recommendation is based on "experiments" done by the experts here that found when the pressure went up by more than that, the flow rate was actually dropping rapidly meaning you were actually filtering less water and thus less efficient.

    Given that your equipment pad is 4' above the water ... meaning your gauge is likely ~7' above the water ... that is likely why you seem to read such a low pressure. It is also dependant on the size and number of your plumbing runs.

    All I can say is that the 20-25% pressure rise is what we recommend, but I can see your concern starting so low. I would just suggest you pay attention to how much the flow may be dropping as the pressure goes up ... maybe a 10psi is too much, but maybe you could get by with more than only a 1 psi rise.

    I do not know anything about the Pleatco grids, sorry.
    Jason, TFP Moderator
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    Re: Filter Sizing?

    Thanks, Jason, that seems to make sense. And, yes the gauge is probably 6'-7' above the water line. I'll try to keep an eye on it a little closer. I see your point about the fixed number guide. I would have thought 5 psi was 5 psi regardless. I can see that if my equipment was at pool level the pressure w/b much higher. I guess the percentage would be the same though?

    Is there an easy way to test for the flow rate? I have 2" PVC. My piping is rather simple, though it may have a a few extra 90's. I only have one skimmer and two outlets, all on the same side of the pool. The piping goes through the wall in the garage and turns down to the crawl space another 90 turn across and into the block wall to the outside where it goes under ground. There must be another 90 turn down to get deep enough to connect to the outlets (steps and deep end) and the skimmer. There is no floor drain. I imagine not letting the pressure to get too high helps keep the DE material (I use Aqua Perl Media) from caking so badly, making it hard to backwash effectively.

    I appreciate the help. I've decided to stick with the DE filter, since I have it. Sand may be a little easier, but backwashing is the same, and that was the part I dislike so much since my drain got clogged, and I have to use the hose again and blow it down my driveway.

    Joe
    34' x 16' Vinyl pool with diving board and slide.

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    Mod Squad jblizzle's Avatar
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    Re: Filter Sizing?

    Mark can do a pretty good job of estimating your flow rate, based on all the details of your setup. But, no easy way to test it ... besides installing a flow meter. There is really very little value added in actually knowing the flow rate ... what would you want it for?

    Just run the pump long enough to keep the water clean to your liking ... and don't worry how many turn-overs it gets ... does not matter. As far as knowing when to clean the filter ... I would think you would most easily notice the lower flow going into the skimmer.
    Jason, TFP Moderator
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