Fresh water system: air getting into water lines

Discussion in 'General Maintenance/Repair Questions' started by onthejob, Jul 8, 2019.

  1. onthejob

    onthejob Member

    237
    May 1, 2013
    Rochester, NY
    2003.5 Sea Ray 340 Sundancer, Raymarine A97 and Quantum radar. Hurley Davits with a Zodiac 310 Zoom
    2x 370-hp MerCruiser 8.1S Horizon with V-Drives turning 4 blade wheels
    2003.5 Sea Ray 340 Sundancer

    Issue: Air is somehow getting into the pressurized water lines causing the 12v water pump to runs 3x longer than normal because it is trying to pressurize the air trapped in the system. I can hear and see air being discharged from each of the faucets (cockpit sink is worst) the first few seconds I turn them on. Once I run all the faucets to bleed the air out, the system is fine for a short period of time. The 12v pump turns off a few seconds after I turn off the faucet like it should and use to. Dockside water works fine.

    1. Water tank is full
    2. Checked all connection - tight. This includes the manifold, pump and faucet connects.
    3. Water screen is clean
    4. Batteries and fresh and plugged in
    5. I have bled ALL the faucets including the head, transom shower and transom faucet

    Question: How is air getting into my 12v pressurized fresh water system? Where should I look next?
     
  2. LUnaCY

    LUnaCY Active Member

    206
    Aug 28, 2018
    Afton, MN
    310 Sundancer 2002
    Mercruiser 5.0 MPI Bravo III
    If you leave the pump on and dont use the faucet does it occasionally repressurize and how often if so?

    If not then the system is tight and the pump itself has a leak prior to the check valve / pressurized side of the pump.
     
    Craig likes this.
  3. onthejob

    onthejob Member

    237
    May 1, 2013
    Rochester, NY
    2003.5 Sea Ray 340 Sundancer, Raymarine A97 and Quantum radar. Hurley Davits with a Zodiac 310 Zoom
    2x 370-hp MerCruiser 8.1S Horizon with V-Drives turning 4 blade wheels
    I don't remember hearing it cycle back on. I'll tell my wife I have a boat project today after work. Sounds like a job for six-pack and a long evening.
     
  4. bobeast

    bobeast Dance the Tide SILVER Sponsor

    Oct 22, 2017
    Isleton, CA
    2002 310DA
    350 MPI w/V-drives
    If your pump is not cycling, then the problem is likely before the pump. I had a crack in the fresh water tank dip tube. Once tank level dropped to about ⅓ the crack was exposed, and air was introduced into the system. Check all fittings between the tank and the pump.
     
  5. frosh coach

    frosh coach Member

    181
    Apr 20, 2011
    Long Island Sound, New Haven CT
    1994 300 Sundancer
    1989 230 Cuddy (SOLD)
    Twin Mercruiser 350 FWC, Alpha 1 Gen II
    i'm going to follow this. I'm having a similar issue.
     
  6. Sublimetime

    Sublimetime Active Member

    766
    Oct 22, 2007
    clifton nj
    420 da
    454
    Pay very close attention to the small filter/screen housing located between the tank and the pump. They tend to allow air to be sucked in around the screw that attaches the bowl to the housing, as well as the o-ring seal.
     

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