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Discuss Feed and Vent fun :DDDDD in the Central Heating Forum area at

  1. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    does the feed and vent need to onto the flow pipework, i have a situation where is would be better if it could go on the return pipework

    something like below

    i think it does due to the vent

    reason for this its an 8m pump and he wont seal it

  2. rpm

    rpm Trusted Plumber

    Edit; see below.
  3. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    but its a friday
  4. rpm

    rpm Trusted Plumber

    What have I told you about laying off the sheep dip. :p
  5. Best

    Best Trusted Plumber

    [I know it is hot weather and around holiday season, but what has happened this forum? Where has everyone gone?]
    Re the question, - Vent would be on the positive side of the pump unfortunately if you did it like in your diagram.
    But I wouldn’t be sure if it would pump over
  6. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    The thing is it would suck air in if I flipped them round to make feed first

    Really wish he would seal the bloody thing 25+ rads

    • Agree Agree x 1
  7. king of pipes

    king of pipes Trusted Plumber GSR

    Come on Shaun you know the answer here bud cold feed and vent needs to be before the pump as the far right diagram you will have air issues and pumping over if not at a push cold feed can go in the return but could still pump over , seal it mate your the heating engineer fit and set a PRV on the filling loop so the system can never be over pressurised is my advise. Cheers kop
    • Like Like x 1
  8. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    Technically it is before the pump :D

    And he won't seal it due to him thinking it won't take the pressure
  9. Gasmk1

    Gasmk1 GSR

    convince him to seal it and use an auto filler set at 1 bar or just below with blow off at 2 bar.
    • Informative Informative x 1
  10. fixitflav

    fixitflav Active Member

    Ideally, should be boiler - open vent - cold feed - pump. That's the best arrangement to vent air, which is most likely to come from the boiler, specially on initial commissioning. Also as the cold feed sets the reference pressure for the system, gives lowest risk of anywhere being below atmospheric pressure, as you obviously don't want inward air leaks.
    But there shouldn't be a problem putting both on the return as your original sketch, if the height between the boiler outlet and the F/E tank is adequate. The point of minimum pressure is then boiler discharge, and = static pressure from the F/E tank minus boiler headloss, so likely to be well above atmospheric with usual boiler headloss figure. 8m seems high for the pump, but if the complete system does have this friction loss, most of that won't be across the boiler.
    Your 3 pump positions diagrams would be more useful if the locations of the boiler and rads were shown. Comments shown are correct, IMO.
    No.1 is poor because the minimum pressure is F/E tank static pressure minus total system loss, so if loss is 8m, could be below atmospheric.
    No.2 is a non-starter as there will be over-pumping if the pump head is above the height from F/E tank TWL to the top of the vent pipe, typically 0.45m, as it almost certainly will be.
    No.3 is OK, could be either of your original options, depending on whether the boiler is to the left of the open vent or between the cold feed and the pump.
  11. Best

    Best Trusted Plumber

    If the system had no push fit, then I would try to convince the customer the benefits of a sealed heating system
  12. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    Already tried won't have it (think it's been diy soldered) :D
    • Funny Funny x 1
  13. sammathias

    sammathias Plumber GSR

    I'd like to think pushfit can with Stand 1bar!! Although I dispise the stuff.
    • Like Like x 1
  14. Best

    Best Trusted Plumber

    Only reason I mentioned push fit as a risk is I hear of some coming apart.
    One customer has the expansion vessel and filling loop in attic and kept the pressure to nearly zero because he said a push fit fitting below his hall floor had once come off. Worry is he had since put hardwood flooring over the hall. :eek:
  15. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    Normally no inserts used
    • Like Like x 1
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