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Discuss Balanced Cold water - Megaflo in the Plumbing Forum area at

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  1. topman870

    topman870 New Member

    Hi There,

    I've just had my heating system fitted and wanted to know where the balanced cold should have been fitted as I've been reading the manual and it says it should be straight after the 3 bar reducing valve.

    Looking at way he did mine was after the 8 Bar pressure Relief Valve and then he has put a ball isolation valuve.

    Is this okay or not? - i've attached where he put it.

  2. Best

    Best Trusted Plumber

    I can't see any problem with it connected there. The 8 bar valve protects the supply pressure to the unvented unit and balanced cold, no mater which side the tee off is.
    But if MIs state immediately after the reducing valve, then I would have done that.
    Why not ask your installer? Post a photo or two of all the unit pipework if you want
  3. scott_d

    scott_d Plumber GSR

    Should be after the prv but before the check valve
    • Agree Agree x 1
  4. topman870

    topman870 New Member

    Ah ok, whats the logic if done inbetween verses after?

    I will call the numpty back but isn't picking up his phone as i left hime a VM so i think he knows he is in the wrong now!
  5. Chuck

    Chuck Active Member

    The 'problem' with the red pipe location is that if the air in the expansion volume inside the Megaflo gets depleted, warm water from the tank will be pushed out of the tank during the heating cycle, past the red T-piece and then out of the PRV. This means the cold water coming via the red T-piece could be contaminated. (I wouldn't want to drink it, anyway.)
    • Agree Agree x 1
  6. topman870

    topman870 New Member

    Thank you for your explanation Chuck.
  7. Best

    Best Trusted Plumber

    I missed the point about the check valve position.
    I notice when I reread the OP that the plumber also fitted a ball isolation valve after the tee??
    It is not permitted to put any valve between the pressure relief valve and the unit, except a drain off. That would mean the safety relief valve could be shut off from the unit!
    Can you post a photo?
    • Agree Agree x 2
  8. moonlight

    moonlight Plumber GSR

    Quite a few combination valves have a take off for balanced water pressure, have you a picture of your valve?
    • Like Like x 2
  9. Gareth Harris

    Gareth Harris New Member

    The guys above are right:

    1. the balanced cold should be after the pressure reducing valve and before the check valve (this prevents the warm water going up the cold pipe as it expands)
    2. there most certainly shouldn't be an isolation valve after the pressure reducing valve

    the installation instructions should details exactly where the balanced cold should be taken from, where there is a combination valve that can accommodate this or if a tee needs cutting in.

    i wonder if your installer is a member of an Competent Persons Scheme and intends to notify building control of this poor installation: Competent person scheme - current schemes and how schemes are authorised - GOV.UK
    • Agree Agree x 1
  10. Darren Jackson

    Darren Jackson Plumber GSR

    Its frightening that he has not followed the MI's and even more frightening he has fitted an illegally placed isolation valve which could render the safety PRV to be nonoperative and potentially have catastrophic consequences to you and the property.
    • Agree Agree x 1
  11. Gareth Harris

    Gareth Harris New Member

    I was trying not to scare anyone!
  12. M1keJ

    M1keJ New Member

    You state he has installed it after the 8 bar PRV? Should be 3 bar? As for installing a balanced cold, combi valves sometimes have this. With regards to the isolating valve, is this on the balanced cold supply, i.e. Cold water to taps, or on the cold feed,i.e. Cold water to cylinder? Fine if a, not fine if b.
  13. Gareth Harris

    Gareth Harris New Member

    I think the "8 bar PRV" being referred to is the expansion relief valve (sometimes referred to as the pressure relief valve) rather than the Pressure Reducing Valve (PRV).
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