Water Pump

Discussion in 'Tech/Mech General' started by Chas17, Oct 6, 2016.

  1. Chas17

    Chas17 Funster

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    In an attempt to diagnose a water pump problem I have been reading the myriad of answers to pump problems using the search facility - to the extent that my head is now pretty much scrambled.
    Symptoms are running more or less continuously when taps are turned off.
    Turning any tap on gives a significant spurt of water followed by normal running.
    Turning taps off turns pump off but it switches on again without demand after about five minutes.
    Turning pump off at selector at this stage and leaving for a while results in protracted running when subsequently selected on.
    My "diagnosis" is an internal leak in the pump allowing water to flow back through the pump into the tank thus requiring priming each time I switch on or if taps are left off for a while.
    I would be grateful for any comments on this.
    The current pump is a Posiflo 3000-151-2000 7L/min 20 psi which I believe is now obsolete and may be replaced by a Shurflo Trail King 7L/20 psi.

    Words of wisdom would be much appreciated.
     
  2. Cavs

    Cavs Funster

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    Is the system fully bled so there's no air in it anywhere? You suggest a leak within the pump, are you sure there's no seepage anywhere else?
     
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  3. pappajohn

    pappajohn Funster Life Member

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    As above......
    Could be the pump, could be a hidden leaky joint.
     
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  4. Chas17

    Chas17 Funster

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    Thanks for the responses. I am presuming that with normal water flow, with no spurting, from all the taps both hot and cold the system is clear of air. Have checked all the joints for tightness and security and there is no hint of leaks or damp.
     
  5. Badknee

    Badknee Funster

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    It may be the pump/ one way valve/pressure switch leaking water back into the tank or you have a leak.(n)
     
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  6. Tootles

    Tootles Funster

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    The pressure switches on Posiflo pumps are notoriously bad. Also, if any foreign matter has got into the diaphragm seal housing, it can stop the diaphragm from passing the water forwards, which will then cause a pressure loss after the pump, telling the pressure switch to remain open. Posiflo pumps also suffer from motor magnet failure. The magnets are stuck into the armature housing with glue. If the pump gets to hot, the glue melts, the magnets come into contact with the spinning armature, which shatters the magnets, therefore dont let it run continually until you can sort out the pressure problem.
    The pump diaphragm is easy to strip down and clean. There are 5 (I think) stainless cross headed bolts in the pump head. Remove them, then carefully separate the diaphragm housing from the pump body and drive shaft. It could be something as simple as lime scale. (y)
     
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  7. Chas17

    Chas17 Funster

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    Thanks Tootles. I shall retrain as a pump engineer over the weekend. If it does turn to rats am I right about Shur flo being the replacement pump?
     
  8. Badknee

    Badknee Funster

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    Ours is a sure flow, easy to strip down and parts are available and cheap enough to replace if totally foobard.
     
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  9. Tootles

    Tootles Funster

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    Either that or a Jabsco. Posiflo pumps are really the cheapest. Jabsco are very good, but can cost twice as much. With water pumps, it always tends to be the cheaper ones that are fitted from new. It all depends how long you intend to keep your present van. However, that's in the sky. Give yours a good internal clean, also check that the spring loaded valves above the diaphragm are seating properly. You can do this by giving each one a 'flick' against the spring.
     
  10. Wagoneer

    Wagoneer Funster

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    Equivalent replacement pump, Shurflo Trail King 7, 20 psi (manufacturers ref 2095-204-112) is available for less than £50.

    Cheapest seems to be from leisureshopdirect for £47 (including vat but excluding p&p).

    Is it worth messing around with your existing pump at that price? I recently bought one to keep in my spare parts emergency box.

    I admire your resolve to try and fix your existing pump (that's what I would probably do) but you do need to consider the long term reliability of such actions and the overall cost effectiveness.

    Assuming of course that it is the pump that is causing the problems.
     
  11. Chas17

    Chas17 Funster

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    Pump engineers course completed! I removed and dismantled the pump and transparent filter. Quite a bit of gunge in both. Pump had a bit of internal limescale. Gave everything a good clean and as far as I could ensured the valves were seating OK. Reassembled and reinstalled and so far all seems to be working fine. Pump is running significantly quieter and does not have any "priming" surge when taps are turned on. So it's fingers crossed really. I'll leave it 24 hours and recheck.

    Thanks to everyone who offered help and advice. I may well buy a replacement pump as a come in handy in the future.
     
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