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Discuss HW Pressure falling after 3 years. Where's the problem? Please help in the Plumbing Forum area at UKPlumbersForums.co.uk.

  1. Andrew Fish

    Andrew Fish New Member

    Hi Team,

    I moved into a new build in 2014 and the HW pressure and flow to all taps over the last 3 years has been good. Recently the HW flow rate has fallen gradually to the point where you can no longer really run a bath at an acceptable flow. The initial pressure on opening any HW tap is good but after a few seconds fades to a low flow. The CW is not affected and has good pressure and flow.
    All hot taps are affected.
    The water enters the building via a pressure reducing valve on which there is a gauge which reads 3.5 bar static pressure.
    There is a water softener in the utility room but when this is by-passed no change is noted to the poor flow of the HW taps.
    On opening a CW tap the pressure gauge under the sink in the utility room falls to about 2 bar during flow and when the CW water tap is turned off it immediately returns to 3.5 bar.
    When the same is done on a HW tap, the pressure falls to be about 2 bar also, but on closing the HW tap the pressure takes longer to return to the 3.5 static pressure reading.
    The mains feeds to an unvented Albion cylinder via a Caleffi 2 bar pressure reducing valve which is used to balance the cold water to the cylinder and the cold supply to all showers and mixers.
    I suspect there is something on the HW side which is obstructing the flow and am wondering if it's something to do with the Caleffi PRV? Do these fail with the symptoms I am seeing? I don't know of anything else, like a blocked filter, in the circuit which could be causing this problem.
    I have attached a picture of the layout which may help.
    Any ideas?
    Thanks,

    AJ

    Balanced Water on Unvented Cylinder
     
  2. jtsplumbing

    jtsplumbing Plumber GSR Top Contributor!!

    Has your in a new build you may have blending valves near the hot taps and these need to be serviced may be dirty filter or they need adjusting.
     
    • Agree Agree x 1
  3. Andrew Fish

    Andrew Fish New Member

    There is a blending valve on the bath I believe, but all the HW taps are affected. Presumably any blending valve fault would only affect the taps it's fitted upstream to?
     
  4. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    Have you had the unvented cylinder serviced?
     
    • Like Like x 1
  5. Best

    Best Trusted Plumber Top Contributor!!

    I instantly thought same, - get the unvented unit serviced and this will sort your problem.
    Unvented units need serviced once a year by a G3 unvented qualified plumber to keep units warranty of (usually) 25 years, but also to keep them functioning 100% and more importantly to have them working safely. They are potentially dangerous
     
  6. townfanjon

    townfanjon Trusted Plumber GSR Top Contributor!!

    Snap ^^^ , probably
     
  7. SimonG

    SimonG Trusted Plumber

    Should have an annual service.
     
  8. Jim Goodenough

    Jim Goodenough New Member

    I notice the braided hose from the combi valve to the expansion vessel dips down, this contravenes regs - have the UHWS unit serviced now and annually as suggested previously by the pro's.
     
  9. sammathias

    sammathias GSR

    Is that correct?
     
  10. Jim Goodenough

    Jim Goodenough New Member

    Yes, did G3 training recently and instructor taught us flexi-hose from combi valve must rise all the way to vessel - reason being water could possibly stagnate / legionella risk.
     
  11. townfanjon

    townfanjon Trusted Plumber GSR Top Contributor!!

    Theres always talk about this on vessels but I have never heard that...
     
  12. sammathias

    sammathias GSR

    Yeah did my resit 6 months ago and have never heard such thing. They change the regs constantly!
     
  13. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    yea they need to be hard piped now

    not that it will affect me as i hate the flexis on them
     
  14. sammathias

    sammathias GSR

    Dont effect me either, just bash a combi in, job done ;);).
     
    • Like Like x 1
    • Funny Funny x 1
  15. Jim Goodenough

    Jim Goodenough New Member

    there was a bloke on the course who says he uses a 22 x 22 x 3/4FI compression tee and screws the vessel straight into the tee - thought that was a great idea.
     
    • Like Like x 1
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