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Thread: low pressure from outflow is filter the problem

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    low pressure from outflow is filter the problem

    I have read as much I can on this forum for hours Great site, helpful people.

    I have owned this house and pool for 5 years. this year since I opened the pool 2 weeks ago, the water outflow pressure from the eye (2) is very low. I opened and cleaned my DE filter and removed each of the grids (8) and cleaned them.

    There is some improvement, but not much. The PSI on the filter is about 27. Some air in basket.

    When I backwash the outflow of water pressure seems very good and the basket has no air. So I am assuming the problem is the filter.

    Do I need to replace the grids OR is there other explanation for this problem

    Appreciate any help.
    Inground vinyl linear pool, 40 X 20 feet, Hayward 3/4 pump, Pentair DE filter

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    JasonLion's Avatar
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    Re: low pressure from outflow is filter the problem

    Welcome to TFP!

    It sounds like you have a restriction in the plumbing that is preventing full water flow. How does your filter pressure compare to what it normally is, is it higher or lower than usual? Also, double check any values you have to make sure nothing is set to partially block the flow of water.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
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    Re: low pressure from outflow is filter the problem

    Thanks for the reply. The Pressure is higher (27) than normal, usually it is about 20 psi. There are no valves to the outflow, since the water from the filter goes to the chlorinator (New water type) and then into the pool through the outlet.

    The near eye (deep end, close to the pump) has good flow (still not as good as before) the farther eye (near shallow end) has very little flow.
    Inground vinyl linear pool, 40 X 20 feet, Hayward 3/4 pump, Pentair DE filter

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    Mod Squad zea3's Avatar
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    Re: low pressure from outflow is filter the problem

    Did you clean out the pump strainer basket?
    TFP Moderator
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    Re: low pressure from outflow is filter the problem

    Yes the pump strainer basket has been cleaned. When I backwash the flow through the backwash hose is very good, which means all the water INTAKE (from skimmer and bottom return) should be fine. Also the pump strainer basket fills up with water when backwashing. but as soon as I switch to filter mode - in a few minutes there is air in the strainer basket - which suggest the outflow through the filter or something else may be the problem

    Even though I cleaned the DE filter grids - they are brown in color, Could they be causing obstruction since they are old?
    Inground vinyl linear pool, 40 X 20 feet, Hayward 3/4 pump, Pentair DE filter

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    Mod Squad Bama Rambler's Avatar
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    Re: low pressure from outflow is filter the problem

    If there is air in the pump basket then there is air getting into the suction line. Could be that the skimmer is sucking air in or a suction side leak somewhere. Check the skimmer weir to make sure it's working properly and not sticking. Another common place is the pump basket lid. Check the o-ring and lube it good with silicon pool lube before you put it back on.
    Dave J. TFP Moderator
    24' x 52" Round AGP. 2hp/¼hp SPL Power-Flo 2-speed pump. 200sqft Waterway Cartridge Filter. 45MHP2(3GPD) Stenner Peristaltic Pump
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    Re: low pressure from outflow is filter the problem

    I open and resealed (with silicone lube) the filter basket. Also the skimmer weir is not stuck - it is kinda floating since there is not much suction there ( it still works) the suction in the skimmer goes up when I only have that on (turn dial to shut off ground suction port).

    Still no change in inflow strength.
    Inground vinyl linear pool, 40 X 20 feet, Hayward 3/4 pump, Pentair DE filter

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    Mod Squad Bama Rambler's Avatar
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    Re: low pressure from outflow is filter the problem

    Does your filter have a multiport valve? If so, then put it on bypass or recirculate, if it has that setting, and let us know what the pressure reads then.
    Dave J. TFP Moderator
    24' x 52" Round AGP. 2hp/¼hp SPL Power-Flo 2-speed pump. 200sqft Waterway Cartridge Filter. 45MHP2(3GPD) Stenner Peristaltic Pump
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    Re: low pressure from outflow is filter the problem

    It does not have a mutliport valve - at least not the one you can just recirculate the water. The 2 pipes bring water from skimmer and bottom vent the motor ..this goes to the the filter ..from there the pipes take it to the chlorinator and out to the outflow.

    I do not know how old my filter grids are, I have owned the pool for 5 years (the pool may be about 13 years old). Not sure if the grids have ever been changed. They only have a couple of tiny holes. Does any one know how ofter the grids should be changed.
    Inground vinyl linear pool, 40 X 20 feet, Hayward 3/4 pump, Pentair DE filter

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    Mod Squad Bama Rambler's Avatar
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    Re: low pressure from outflow is filter the problem

    If they have holes of any size they shoud be repaired and if they can't be repaired they need to be replaced.

    Have you done a thorough cleaning of the grids?
    Dave J. TFP Moderator
    24' x 52" Round AGP. 2hp/¼hp SPL Power-Flo 2-speed pump. 200sqft Waterway Cartridge Filter. 45MHP2(3GPD) Stenner Peristaltic Pump
    Pool School ----- Pool Math ----- TF-Test Kit

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    Re: low pressure from outflow is filter the problem

    I had the service guy show up today - even though he was supposed to come next Wednesday - so i would have time to sort things out here.

    I was not home, He left a message saying that my return line was not working well. Here is his explanation he gave - that I have put granulated chlorine tabs in my chorinator which result in build up of gas in line and caused problem with return line so they are no longer working well. Thus low output of water. That is causing the grids to burst due to back pressure, since water has no place to go.

    I have the "New Water" chlorine cartridge system for chlorinating the pool.

    My Question is doesn't everyone use chlorine tabs to chlorinate water returning to the pool. So why would there be gas build up and the pipes not work.

    HE also recommended I get a new filter ($1100) and that my water output would have to be switched to the vacuum return line since the other output line is not working well.

    I could really could use some help from you guys - what the next step should be
    Inground vinyl linear pool, 40 X 20 feet, Hayward 3/4 pump, Pentair DE filter

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    Melt In The Sun's Avatar
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    Re: low pressure from outflow is filter the problem

    Wow, that guy gave you a lot of BS. Never call him again! Gas blocking a return line and bursting grids as a result is complete hogwash.

    You could try a drain king or something to see if you can find/fix the blockage. Other folks here have much ore experience than I, hopefully they'll be along to help.
    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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    Mod Squad Bama Rambler's Avatar
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    Re: low pressure from outflow is filter the problem

    Listen to MITS, never call that guy again. Even if there are problems his explanation is atrocious.

    Can you post a picture of your plumbing and equipment? We can probably give you some pointers on how to troubleshoot the problems.
    Dave J. TFP Moderator
    24' x 52" Round AGP. 2hp/¼hp SPL Power-Flo 2-speed pump. 200sqft Waterway Cartridge Filter. 45MHP2(3GPD) Stenner Peristaltic Pump
    Pool School ----- Pool Math ----- TF-Test Kit

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    Re: low pressure from outflow is filter the problem

    Sorry for the late followup - was away for work.

    ALso I just ordered and installed new grids for my DE filter - just in case the grids were blocked and causing low outflow.

    The low outflow through both outlet is still very low (one has no flow) - so the water is staring to get murky.

    As requested I am posting some pictures of the pump.

    When I backwash the flow throw back wash is very good - so the motor works, the suction line - skimmer and ground-in flow works.)

    Which means there is something going on with the outflow pipes.

    I had a chance to talk to the manager of the above guy who came to service (they orginally build the pool) He mentioned that the pipes for outflow are "flexpipes" and can be damaged if chlroine leaks in to it. I use the "new water chlorinator' but have been cutting the cartridge and adding 3 inch tabs from leslie.

    What should be my next step - I appreciate all the help
    Attached Images Attached Images
    Inground vinyl linear pool, 40 X 20 feet, Hayward 3/4 pump, Pentair DE filter

  15. Back To Top    #15

    Re: low pressure from outflow is filter the problem

    Have you tried a drain king in the return lines from the equipment back to the pool? Sounds like a possible blockage?

    If flex hose was used for the return lines, perhaps the ground settled causing a kink? Not sure if this could happen with flex pipe. No idea how chlorine could cause a kink or other blockage, and if the pipe split you'd be losing water and that still wouldn't explain the back pressure.

    Sure sounds like a blockage.

  16. Back To Top    #16
    Melt In The Sun's Avatar
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    Re: low pressure from outflow is filter the problem

    I could be crazy, but I don't see any kind of backwash valve in your plumbing; how do you do it?
    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!
    TF Test Kits -- PoolMath -- Pool School
    Make each day your masterpiece. - John Wooden

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