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joerg68's avatar
joerg68
Nomad III
Jun 10, 2017

Solved: How to find vacuum leak in water supply line?

Hi all,

this week we picked up our new camper, a Northstar Arrow.

The camper is fantastic and we are very happy with it - except for one problem with the water supply that has us all stumped:

The water pump does not provide constant pressure, sputters, and frequently loses prime. It seems to suck in air somewhere. Especially when we take just a little bit of water, it tends to lose the vacuum and runs dry until we take a lot of water again. Then it primes and works, but sputters frequently. The issue is a bit better when the tank is full, and gets worse as the tank empties.

What we have done so far:
- Checked the tank vent hose - it is free, no kinks or obstructions
- There are no water leaks, anywhere. It holds pressure fine on the pressure side
- All fittings are firm to the touch and dry from tank to pump
- We have switched the winterizing valve and sucked water through the winterizing hose. The effect remains the same.

This would put the problem somewhere between the winterizing valve and the pump (including both), right?

Anyone have an idea how to find the vacuum leak short of disassembling the whole water line from tank to pump? It is made up of around 8 or 10 short sections of solid plastic pipe. And a number of elbows and the one winterizing valve. You can not see if and where any bubbles are introduced. The strainer is installed with the clear lid facing away from us...

To make matters more interesting, we are still on our shakedown trip and have no useful tools with us.

What would you do to find the leak?
Truck Campers
  • Toddupton's avatar
    Toddupton
    Explorer
    Jun 10, 2017
    Start by hooking a hose directly to the pump and put the other end in a bucket of water and see if you have a bad pump.
  • Old-Biscuit's avatar
    Old-Biscuit
    Explorer III
    Jun 10, 2017
    Check pump strainer....might not be tight or might be cracked
    Also check pump casing for any signs of cracks

    Sucking in air can only happen on tank side of pump and same symptoms using winterizing kit then YES issue is between that section and pump itself

    With pump OFF

    See if you can 'fill' suction side of line/strainer/pump using winterizing kit and then place TP around fittings/clamps/connections/strainer---pump casing and look for wet spot (might have to loosen strainer a bit so water can run in/fill up line)
  • Kayteg1's avatar
    Kayteg1
    Explorer II
    Jun 10, 2017
    My favorite vacuum test is by using a cigar.
    IT HAS TO BE CUBAN FOR QUALITY OF TEST.
    Start the pump and blow the smoke around the piping.
  • covered_wagon's avatar
    covered_wagon
    Explorer
    Jun 10, 2017
    My hose end fits snug to the freshwater fill and I can build air pressure inside the freshwater tank when filling if I place my finger over the vent hole. You might be able to do this but not letting it pressure go up very much at all is important. With the water pump shut off and all faucets/ valves closed, you might be able to see the leak on the suction side of the water pump then. Be ready with towel to mop up, but I doubt it would be very much water and damage anything anyway.

    On another note... it would be best if you used a compressor and set the air pressure very low. it wouldn't take much to get it to bleed water out the leak..

    Try removing the cap to the sediment filter and retighten, but look for a good 'O' ring seal too.
  • joerg68's avatar
    joerg68
    Nomad III
    Jun 10, 2017
    Thanks for all the tips! No smokers here, but the idea sounds like it could work.

    It is evening here now. I'll see if I can do any tests on the road tomorrow - if not, we'll have to wait till we get home mid-week.

    I'll let you know when I have results ;-)

    Thanks a lot,
    Joerg
  • mkirsch's avatar
    mkirsch
    Nomad II
    Jun 12, 2017
    I know it would be somewhat inconvenient, but that sounds like a warranty issue to me.
  • jimh406's avatar
    jimh406
    Explorer III
    Jun 12, 2017
    I think I'd talk to the dealer as well. It's brand new ... it should just work assuming the holding tank has enough water to pick up water and the winterizing switch if equipped is in the right position.
  • unbob's avatar
    unbob
    Explorer
    Jun 12, 2017
    I had the exact same problem! In my case it turned out to be a worn-out 'O'-ring on the strainer housing. Or it could be the strainer "cover/cap" is not screwed-on tight enough. There was no water leakage - only air being sucked-in. I would check this before proceeding with other troubleshooting.

    Also, the 'O'-rings on the inlet & outlet hose fittings on the pump can also eventually "give-out" and cause a water leakage (been there/done that!) - so good idea to replace those every 5-6 years as easy preventive maintenance.
  • joerg68's avatar
    joerg68
    Nomad III
    Jun 12, 2017
    So we are still on the road with the vacuum leak. After all, it is a TC and don't they all have their quirks...

    Re. warranty issue: yes, it sure is. But the effort in time and money to take it to the dealer is not worth it, and travelling with an American made RV in Europe has tought us to be self-reliant. I am sure the dealer would send a new pump if the old (still new) one turns out to be defective.

    When we get back home I will see if I can provoke a water leak from the winterizing hose side. And then I will probably do some disassembly and cleaning and reassembly. It is a new camper, I need to get to know it inside out, right? ;-)

    If that doesn't fix it, I need to find a local shop who is willing to take a look.

    Thanks for all the feedback and I'll keep you posted

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