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Thread: Public Pool Flow & Turnover Problem

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    Default Public Pool Flow & Turnover Problem

    [ Note to posters: this is a public pool. Very different rules apply! PoolDoc. ]

    I'm getting about 80 gpm. I'll never get to the 244 gpm required to turn my pool in 6 hours. I would, however, like to improve upon the 80 gpm.

    88,000 gallons, two 500 lb sand filters, 2 hp and 1.5 hp pump. Two 3 inch pipes return from the skimmers and bottom (1 pipe for each). Pipes drop to 1.5 inch before each pump. Each pump feeds a filter (1.5 inch pipes) and then the pipes combine again in a 3 inch junction.

    Each 1.5 inch pipe should theoretically give me 74 gpm. Filters are rated for "up to" 98 gpm. I should theoretically be able to achieve 140 without changing pipes or filters (I think).

    Before I spend the money, I am trying to figure out if larger motors on my pumps will give me extra flow. Are my assumptions above incorrect? Any thoughts?

    Russ
    Last edited by PoolDoc; 07-08-2011 at 10:32 AM. Reason: add commercial note
    88,000 gallons (chlorine) -- Two 500 lb sand filters, gunite/plaster,
    2 hp Hayward pump, 1.5 HP Pentair

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    Default Re: Flow / Turnover Problem

    Hi Russ and welcome to the Pool Forum. I am not the equipment/plumbing expert around here, so, trust me, you don't want my advice about your situation!

    But there are some here who will be able to assist you. Once your registration is complete, your post will be moved out into the other areas of the forum where it will be viewed by more people who may be able to help you.

    Glad you found us!

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    Default Re: Flow / Turnover Problem

    To answer your question, it's necessary to actually do some hydraulic calculations, AND to know and consider the pump curves of your two pumps.

    But, I'm puzzled by your reference to 244 GPM being "required". As far as I know, there are no requirements of flow on residential pools.

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    Default Re: Flow / Turnover Problem

    Quote Originally Posted by watervale View Post
    I'm getting about 80 gpm. I'll never get to the 244 gpm required to turn my pool in 6 hours. I would, however, like to improve upon the 80 gpm.
    Why? Most pools do fine with 1 to 2 turnovers per day unless this is a public pool.

    [EDIT: As noted above, it IS a public pool. Very different rules apply! PoolDoc. ]


    Also, if 80 GPM is the combined flow rate, that would be very low. A 1.5 HP AND a 2 HP in parallel should produce well over 180 GPM on low head loss plumbing. Why do you believe the flow rate is so low?



    Each 1.5 inch pipe should theoretically give me 74 gpm. Filters are rated for "up to" 98 gpm. I should theoretically be able to achieve 140 without changing pipes or filters (I think).
    There are no theoretical limits to flow rates in pipes, only recomendations. Water can travel as fast as the pump can deliver.


    What are the two pump model #'s and both filter pressures?

    How far is it from the equipment to the pool?
    Last edited by PoolDoc; 07-08-2011 at 10:29 AM.
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    Default Re: Flow / Turnover Problem

    [ Note to posters: this is a public pool. Very different rules apply! PoolDoc. ]

    88 THOUSAND GALLONS??????? That's not a pool, it's a lake! That's 30'*50' if it's 8' deep everywhere! Or, if it averages 6' (more likely) it's likely to be 75' long and 26' wide. I think our town pool might be that long.....

    Carl
    Last edited by PoolDoc; 07-08-2011 at 10:31 AM.
    Carl

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    Default Re: Flow / Turnover Problem

    [ Note to posters: this is a public pool. Very different rules apply! PoolDoc. ]

    LOL. Inherited responsibility for neighborhood non-profit. 3 feet at one end, 10 feet at other.

    County requirement for turnover is 6 hours. Pitot flow meter shows 80. Not sure if it has enough horizontal length to be accurate, but if it's anywhere close, we have low flow.

    Pumps are 1.5 to 2 feet above water and about 8-12 feet from water's edge on the shallow end. I'll have to go by tomorrow and look up the models. I was up there tonight putting a snake in the skimmers. 4 of them and only 1 has decent flow. Baskets float up. Didn't find any blockage (yet).

    One pump doesn't have bubbles, one has small ones. I don't see any bubbles in the water coming out from the returns.

    Filter pressure (on top) is 10-12 psi. Goes up to about 15-20 after 1-2 weeks without backwashing. I put the pumps on recirculate and don't see any improvement.

    BTW, this forum is phenomenal. I didn't know zilch about pools 4 months ago. I've fixed a ton of problems in 3 months -- balanced the water with BBB, fixed the chlorinators, replaced the sand, etc, etc, etc with the information here. Thanks a ton everyone!!!
    Last edited by PoolDoc; 07-08-2011 at 10:30 AM.
    88,000 gallons (chlorine) -- Two 500 lb sand filters, gunite/plaster,
    2 hp Hayward pump, 1.5 HP Pentair

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    Default Re: Flow / Turnover Problem

    Watervale,

    My site, PoolForum.com, is focused on residential pools. Few here, besides myself have experience with commercial pools. I'll help you . . . as I have time.

    But, for starters, take a full set of digital photos of your pumps and piping and send them to poolforum AT gmail DOT com.

    Also, if you don't already have one get BOTH a K2006C (you need the larger one) AND a couple of K1000 OTO/phenol red kits for quick testing.

    If you don't already know, on your pool, you MUST keep a good chlorine level 100% of the time..

    One other key issue is code enforcement. Here locally, I'm running a HIGH CYA pool at 10 - 20 ppm, because I can't trust the staff to do what they are told. However, I have to take a 2 - 4 pt 'hit' on the code -- 2 for high Cl and 2 for high CYA . . . if his 'strips' (!!) are working well that day. However, some codes will force a re-inspection for those 'violations' which makes them a non-option.

    So, tell me what your code entity is, and how you are inspected. If possible, post a link to whatever pool code you are under.

  8. #8
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    Default Re: Flow / Turnover Problem

    [ Note to posters: this is a public pool. Very different rules apply! PoolDoc. ]

    We had an initial inspection and will get a brief inspection once during the summer. Code enforcement is fair, not brutal.
    http://health.state.ga.us/pdfs/envir.../poolrules.pdf Section 290-5-57-.07 describes turn over requirements.

    I'm sending pictures to you today. I didn't want to post a reply until I did some more home work -- I don't want to waste your time.

    I do have air in at least one pump. I couldn't see it coming out of the returns until I jumped in the pool and held my hand to them. Tiny, tiny bubbles.
    I did find some trash in the 2 HP impeller. I get about 90 GPM now with both pumps on. Made sure both drain plugs were tight.

    I put a 25 foot snake in the skimmers, nothing. Put it in the skimmer return via the pump, no issues that I could find.

    The farthest skimmer still barely has any suction and the basket just floats.....
    Last edited by PoolDoc; 07-08-2011 at 10:31 AM.
    88,000 gallons (chlorine) -- Two 500 lb sand filters, gunite/plaster,
    2 hp Hayward pump, 1.5 HP Pentair

  9. #9
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    Default Re: Flow / Turnover Problem

    I'll watch for the pics. -Ben

    Here they are:

    Pump room


    Multiport label


    Piping


    Pump #1


    Pump #1 label


    Pump #2


    Pump #2 label
    Last edited by PoolDoc; 07-10-2011 at 04:40 PM.

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