Become a TFP Supporter Pool Math Forum Rules Pool School
Results 1 to 6 of 6

Thread: Pentair FNS Hi-Flow backwash valve leaking to waste

  1. Back To Top    #1

    Pentair FNS Hi-Flow backwash valve leaking to waste

    I have a Pentair FNS filter with a Hi-flow backwash valve. The top was cracked at the bolt holes and leaking so I replaced the top along with the diverter gasket. I have adhesived the gasket in place as recommended and checked and re-checked the correct alignment of the valve top, but still when I turn the system on in the filter position, it leaks water out to the waste discharge outlet. I am stumped as to why this is happening. Can anyone provide help to fix this issue? Thanks
    15,300 gallon above ground pool
    Hayward S210T sand filter
    Cyclone 2 speed pool pump

  2. Back To Top    #2
    Mod Squad Bama Rambler's Avatar
    Join Date
    Jun 2009
    Location
    SouthWest Alabama
    Posts
    22,347

    Re: Pentair FNS Hi-Flow backwash valve leaking to waste

    Welcome to TFP.
    Remove the top hat again and closely inspect the gasket as well as the partitions. If there are no cracks or nicks then lube it with silicon pool lube and carefully put it back together.
    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

  3. Back To Top    #3

    Re: Pentair FNS Hi-Flow backwash valve leaking to waste

    I have checked for cracks and couldn't visually see any. Does the diverter gasket need to be installed a certain way. 1 side has a square sealing area while the other side has just a thin line of rubber as the sealing area.

    Also when you say silicone lube are you referring to a lube like Aladdin's Magic Lube?
    15,300 gallon above ground pool
    Hayward S210T sand filter
    Cyclone 2 speed pool pump

  4. Back To Top    #4
    Mod Squad Bama Rambler's Avatar
    Join Date
    Jun 2009
    Location
    SouthWest Alabama
    Posts
    22,347

    Re: Pentair FNS Hi-Flow backwash valve leaking to waste

    Any 100% silicon lube will do. Look for deep gouges along the sealing surface too. Your spring may be weak allowing the water pressure to overcome it.
    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

  5. Back To Top    #5
    no-mas's Avatar
    Join Date
    Jun 2008
    Location
    FL
    Posts
    405

    Re: Pentair FNS Hi-Flow backwash valve leaking to waste

    Could you have installed it backwards? What happens if you set it to backwash?
    18k gal inground, everbrite finish, 505 sq ft; 1.5 hp two speed whisperflow; rheem 5100ti 100k btu heat pump; 3 sheer descent falls; DE filter; swg (cell out and using trichlor for now)

  6. Back To Top    #6

    Re: Pentair FNS Hi-Flow backwash valve leaking to waste

    The top is new so I don't think that the spring would be at fault. The diverter gasket has one side the has a square lip in the middle that matches the channel on the valve bottom. The other side of the gasket is a thinner lip. I've tried both ways without any luck. I'm starting to think there is a hairline crack in the bottom housing that I can't see. It may open up as the pressure inside builds and then leaks out to waste.
    When I move the handle to different positions on the valve it still leaks out to waste.
    15,300 gallon above ground pool
    Hayward S210T sand filter
    Cyclone 2 speed pool pump

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •