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Thread: Advice on pump flow & pressure

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    Advice on pump flow & pressure

    I'm looking for advice on whether or not my pump flow & pressure is too low. I don't have enough experience on what 'normal' looks like, so would appreciate some advice.


    (Sorry for the metric units here)


    - My pool is below ground, 11x2.4x1.3m in size and about 33,000 cubic liters
    - The pump is somewhere between 20 and 30 meters from two eyeball socket jets
    - The pressure from the jets feels low - I can cover both easily with my hands, and when the pump is on it barely disturbs the surface of the water. I feel like the when the pool was first installed the pressure was higher, and you could see the pump was on by the disturbance the jets made on the surface of the water.
    - Suction when I vacuum the pool is ok(ish) (the suction point is the other end of the pool - so 11 meters closer to the pump). I have to vacuum slowly to suck stuff up.

    - The pressure on the filter usually sits between 150 to 175 KPA, depending on when I've cleaned the cartridge. It drops to 50 KPA if I remove the filter entirely.
    - The cartridge is really clean - including between the pleats, I don't think this is a problem. I purchased some product, soaked it for a week and sprayed it out with a high pressure hose
    - The pump is a Hurlcon/Astral CTX400 Pump (Hurlcon/Astral CTX400 Pump)


    1. Is the pressure too low to efficiently clean the pool water?
    2. If so, would I be better off moving the pump closer to the pool, or buying a bigger pump? (or both?)

    Cheers, McOz
    Last edited by McOz; 03-01-2016 at 10:39 PM. Reason: specified pump model

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    mas985's Avatar
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    Re: Advice on pump flow & pressure

    Assuming I am doing the conversion correctly, 150 KPA is about 22 PSI which I consider on the high side.

    Also, slower flow works better for filters so I wouldn't be too concerned about that. However, if the flow is lower than you remember and the pressure is lower than you remember, then that points to a suction side blockage or impeller blockage.

    However, this statement:

    - The pressure on the filter usually sits between 150 to 175 KPA, depending on when I've cleaned the cartridge. It drops to 50 KPA if I remove the filter entirely.
    Points to an issue with the filter. You should not have that much pressure loss over the filter. What kind and size filter is this?
    Mark
    Hydraulics 101; Pump Ed 101; Pump/Pool Spreadsheets; Pump Run Time Study; DIY Acid Dosing; DIY Cover Roller
    18'x36' 20k plaster, MaxFlo SP2303VSP, Aqualogic PS8 SWCG, 420 sq-ft Cartridge, Solar, 6 jet spa, 1 HP jet pump, 400k BTU NG Heater

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    Re: Advice on pump flow & pressure

    Welcome to the forum McOz

    If you can add you're pools info to your signature it will be helpful later on as the thread gets longer. How to - - > Pool School - Getting Started

    How long have you had this pool and the equipment ?? Added anything new or repaired to the equipment recently ??
    How does your water look and have you had any problems with clarity with the present setup ??
    Has the flow always been this was or did it used to be stronger ??
    '70s IG Vinyl 32K gal, Lazy L, Hayward SuperPump 1.5hp 120V, S240 Sand Filter W/DE
    Solar Blanket, Well Water, Borax Added, TF-100 tester. ? too cold
    1979, 275gal Conway Emerald Spa P-100-2, ES-2 Spa Pack, bromine floater, indoor
    TF-100, Best test kit - TFTestkits.net
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    Re: Advice on pump flow & pressure

    Quote Originally Posted by mas985 View Post
    What kind and size filter is this?
    The Filter is a ZX 50 (ZX Pool and Spa Cartridge Filter | AstralPool)

    The pressure drop from removing the cartridge from the filter didn't worry me so much as the flow was pretty much 'straight through' and unimpeded by the cartridge. Maybe it is an issue?

    Quote Originally Posted by Kiss4aFrog View Post
    How long have you had this pool and the equipment ?? Added anything new or repaired to the equipment recently ??
    How does your water look and have you had any problems with clarity with the present setup ??
    Has the flow always been this was or did it used to be stronger ??
    The pool was installed new as part of new build house and is about 2.5 years old. I'm only now learning how to look after and maintain it as previously we had a pool guy. I've had a couple of issues with water clarity - requiring lots of chemicals and multiple vacuums to resolve. When we first got the pool I remember we could look outside and tell the pump was on because of the disturbance in the water surface above the jets. Now, you can't tell the pump is on unless you stick your arm in the water, in front of the jets to feel the flow.

    Thanks for the welcome, and sig updated

    - - - Updated - - -

    The pump, filter, pre filter cyclone spinner thing and chlorination all look to be in good working order - there's not odd noises, smells or obvious wear or damage.

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    mas985's Avatar
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    Re: Advice on pump flow & pressure

    Quote Originally Posted by McOz View Post
    The pressure drop from removing the cartridge from the filter didn't worry me so much as the flow was pretty much 'straight through' and unimpeded by the cartridge. Maybe it is an issue?
    When I remove the cartridges in my filter, I don't get any change in pressure. That is the sign of a good cartridge filter.

    However, you have a very small cartridge filter (~50sq-ft) but the manual does not show a head curve for the filter so I don't know if that is normal or not. Pentair has a 50 sq-ft filter and the manual has only one head curve for all the filters which means you really shouldn't see much head loss due to the cartridge.

    Are you sure the cartridge did not get calcified somehow?

    Also, when you took out the cartridges, did you feel the water returns and did they feel more normal?
    Mark
    Hydraulics 101; Pump Ed 101; Pump/Pool Spreadsheets; Pump Run Time Study; DIY Acid Dosing; DIY Cover Roller
    18'x36' 20k plaster, MaxFlo SP2303VSP, Aqualogic PS8 SWCG, 420 sq-ft Cartridge, Solar, 6 jet spa, 1 HP jet pump, 400k BTU NG Heater

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    Re: Advice on pump flow & pressure

    Hmm, I gave the cartridge a clean on the weekend after vacuuming the pool - the pleats all seemed reasonably good. I'll pull it again and have a closer look. I didn't feel the returns - so I'll do that do, thanks for the suggestion.

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    mas985's Avatar
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    Re: Advice on pump flow & pressure

    A good soak in TSP might help and even an acid bath afterwards to make sure.
    Mark
    Hydraulics 101; Pump Ed 101; Pump/Pool Spreadsheets; Pump Run Time Study; DIY Acid Dosing; DIY Cover Roller
    18'x36' 20k plaster, MaxFlo SP2303VSP, Aqualogic PS8 SWCG, 420 sq-ft Cartridge, Solar, 6 jet spa, 1 HP jet pump, 400k BTU NG Heater

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    Re: Advice on pump flow & pressure

    Replaced the filter cartridge, pressure back to 80Kpa, everything is right with the world

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    Re: Advice on pump flow & pressure

    You might try updating your signature again. Maybe you forgot to "save", "save changes" down at the bottom.

    Good you hear you have your circulation back
    '70s IG Vinyl 32K gal, Lazy L, Hayward SuperPump 1.5hp 120V, S240 Sand Filter W/DE
    Solar Blanket, Well Water, Borax Added, TF-100 tester. ? too cold
    1979, 275gal Conway Emerald Spa P-100-2, ES-2 Spa Pack, bromine floater, indoor
    TF-100, Best test kit - TFTestkits.net
    Please help keep the lights on, become a TFP Supporter!

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    Re: Advice on pump flow & pressure

    Or make sure the show sig box is checked on lower right below the text box. Once it is checked it should stay checked from now on.
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    mas985's Avatar
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    Re: Advice on pump flow & pressure

    Quote Originally Posted by McOz View Post
    Replaced the filter cartridge, pressure back to 80Kpa, everything is right with the world
    Did you ever try soaking the old cartridge in tsp then acid?
    Mark
    Hydraulics 101; Pump Ed 101; Pump/Pool Spreadsheets; Pump Run Time Study; DIY Acid Dosing; DIY Cover Roller
    18'x36' 20k plaster, MaxFlo SP2303VSP, Aqualogic PS8 SWCG, 420 sq-ft Cartridge, Solar, 6 jet spa, 1 HP jet pump, 400k BTU NG Heater

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    Re: Advice on pump flow &amp; pressure

    Done, thanks

    - - - Updated - - -

    Quote Originally Posted by mas985 View Post
    Did you ever try soaking the old cartridge in tsp then acid?
    yes, I'd soaked it for about 4 days a couple of weeks ago in Hydrochloric acid. When I pulled the cartridge out on the weekend, there was an algae with a thin film covering it deep in the pleats of the cartridge. Plus the cartridge was about 2.5 years old so I figured a new one was in order. Thanks for the advice, glad I didn't have to move the pump & filter closer to the pool as that would have been costly.
    Below ground, fibreglass pool. 11m x 2.4m x 1.3m = 33000 cubic liters
    Pump: CTX 400 Hurlcon/Astral CTX400 Pump
    Chlorinator: VX 7TL V3 VX Salt Chlorinator | AstralPool
    Filter: ZX 150 ZX Pool and Spa Cartridge Filter | AstralPool

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