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  1. #1
    Join Date
    Aug 2007
    Location
    Suffolk
    Posts
    5,080

    Default Possible airlock in domestic supply

    Hi,
    Before the winter I drained the water system by running all the taps H&C until dry to avoid any risk of frost damage.
    Today I refilled the water tank, switched on the pump with the taps open and expected some gurgling then water to flow forth.
    However, all I got was an occasional slight dribble from the galley Cold tap, nothing in the heads or either Hot tap. The pump was whirring away happily and not getting hot or sounding odd.

    I am guessing I have an airlock, but how best to clear?

    The only bit of the plumbing that is accessible - and that not easy! - is at the calorifier. The main cold feed is teed here with a supply to the calorifier and the other side going on to the cold taps in the galley and heads. It is a "high" point in the run of the plumbing and I am hoping that disconnecting the cold pipe here might allow air to escape. Should this work or is there a better method known to forumites?

    The pump is also reasonably accessible.

    TIA

  2. #2
    Join Date
    Nov 2009
    Location
    Home UK Midlands / Boat Croatia
    Posts
    18,602

    Default Re: Possible airlock in domestic supply

    If you don't have easy access to one of the water hoses after the pump, the easiest thing to so is probably to use a piece of pipe over a single tap and suck with the pump running until you clear the air lock. The lowest tap will be best but any should do.

    If you do have access to any pipe after the pump, then break it there and suck directly.

    Richard

  3. #3
    Join Date
    Oct 2004
    Location
    Firth of Forth
    Posts
    2,603

    Default Re: Possible airlock in domestic supply

    It sounds as though your pump isn't self-priming so it's trying to pull air through the system and failing.

    I'd suggest trying either pressurising the tank slightly (block any overflow and a couple of strokes from an air pump into the filler) before turning on the pump and opening the taps one by one.

    If you can't do that, then lowering the pressure at the tap is another possibility (turn the pump on, open the tap and suck hard.)

    Good luck!

  4. #4
    Join Date
    Jul 2002
    Location
    Home: Kent. Boat: Chichester
    Posts
    43,172

    Default Re: Possible airlock in domestic supply

    Quote Originally Posted by Leighb View Post
    Hi,
    Before the winter I drained the water system by running all the taps H&C until dry to avoid any risk of frost damage.
    Today I refilled the water tank, switched on the pump with the taps open and expected some gurgling then water to flow forth.
    However, all I got was an occasional slight dribble from the galley Cold tap, nothing in the heads or either Hot tap. The pump was whirring away happily and not getting hot or sounding odd.

    I am guessing I have an airlock, but how best to clear?

    The only bit of the plumbing that is accessible - and that not easy! - is at the calorifier. The main cold feed is teed here with a supply to the calorifier and the other side going on to the cold taps in the galley and heads. It is a "high" point in the run of the plumbing and I am hoping that disconnecting the cold pipe here might allow air to escape. Should this work or is there a better method known to forumites?

    The pump is also reasonably accessible.

    TIA
    If you can bleed the air from a high point try it.

    other wise briefly disconnect the hose from the pump suction to ensure a good flow getting to there. Also check the pump suction strainer,

    Disconnect hose from pump discharge to bleed any air out of the pump itself ........ this may be all you have to do ... but don't forget to check and clean the suction strainer.

    If you dont have a pump suction strainer you may well have stirred up debris in the tank and got it into the pump valves. If that has happened you may well have to strip the pump and clean any muck from the valves.

  5. #5
    Join Date
    Aug 2007
    Location
    Suffolk
    Posts
    5,080

    Default Re: Possible airlock in domestic supply

    Some useful suggestions for me to try, many thanks, I will advise how I get on.

  6. #6
    Join Date
    Aug 2017
    Posts
    84

    Default Re: Possible airlock in domestic supply

    It may be worth checking whether there is a pressure relief valve on the top of the calorifier. If so, there may be a red knob to rotate to vent air. This is what mine has. It's easier than breaking pipe joints.
    Good luck.

  7. #7
    Join Date
    Jun 2001
    Location
    UK East Coast
    Posts
    1,739

    Default Re: Possible airlock in domestic supply

    Quote Originally Posted by Leighb View Post
    Hi,
    Before the winter I drained the water system by running all the taps H&C until dry to avoid any risk of frost damage.
    Today I refilled the water tank, switched on the pump with the taps open and expected some gurgling then water to flow forth.
    However, all I got was an occasional slight dribble from the galley Cold tap, nothing in the heads or either Hot tap. The pump was whirring away happily and not getting hot or sounding odd.

    I am guessing I have an airlock, but how best to clear?

    The only bit of the plumbing that is accessible - and that not easy! - is at the calorifier. The main cold feed is teed here with a supply to the calorifier and the other side going on to the cold taps in the galley and heads. It is a "high" point in the run of the plumbing and I am hoping that disconnecting the cold pipe here might allow air to escape. Should this work or is there a better method known to forumites?

    The pump is also reasonably accessible.

    TIA
    I have this problem after a winter drain-down too. I fitted a new jabsco pump 2 years ago and although it works very well, is is not very good at self priming. It is not an airlock causing my problem. Luckily, my hoses have snap connectors onto the pump so I just break the seal at the pump outlet hose with the pump running. As soon as water starts to spurt out, seal up the connection. I have done this successfully after two winters now.

    Www.solocoastalsailing.co.uk
    Last edited by Plum; 25-03-19 at 20:25.

  8. #8
    Join Date
    May 2001
    Location
    North Wales, sailing Aegean Sea or Menai Strait
    Posts
    21,567

    Default Re: Possible airlock in domestic supply

    Quote Originally Posted by Plum View Post
    I have this problem after a winter drain-down too. I fitted a new jabsco pump 2 years ago and although it works very well, is is not very good at self priming. It is not an airlock causing my problem. Luckily, my hoses have snap connectors onto the pump so I just break the seal at the pump outlet hose with the pump running. As soon as water starts to spurt out, seal up the connection. I have done this successfully after two winters now.

    Www.solocoastalsailing.co.uk
    I agree. You cannot have an airlock downstream of the pump. The problem lies on the suction side - strainer, pump valves or inlet in the tank.
    Answers to some technical queries at new website http://coxeng.co.uk

  9. #9
    Join Date
    Nov 2009
    Location
    Home UK Midlands / Boat Croatia
    Posts
    18,602

    Default Re: Possible airlock in domestic supply

    Quote Originally Posted by vyv_cox View Post
    I agree. You cannot have an airlock downstream of the pump. The problem lies on the suction side - strainer, pump valves or inlet in the tank.
    As Plum says, it's probably the pump not able to self-prime because of air in the pump and it can't pump air, although it will pump water it finally gets there .... and sucking on the downstream side is a good way to clear the air.

    I've always called that an airlock because the trapped air is locking (i.e. stopping) the water flow but it might not be the correct technical term.

    Richard

  10. #10
    Join Date
    Aug 2017
    Posts
    84

    Default Re: Possible airlock in domestic supply

    The pump may be above the free surface level in the tank. If so, keep the tank topped up and, perhaps, overflowing while the pump primes.

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