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Discuss Expansion Relief Valve in the Plumbing Forum area at

  1. John H

    John H New Member


    I am relatively new to installing and repairing unvented cylinders, having worked largely on vented systems up until now. Today I have come across a megaflow that has a TPRV but no Expansion Relief valve on the inlet. Is there ever a situation where the ERV isn't required or does not have to be fitted? Thanks for your help.

  2. ShaunCorbs

    ShaunCorbs Trusted Plumber GSR Top Contributor!!

    Are you G3 registered?
    • Agree Agree x 1
  3. Best

    Best Trusted Plumber Top Contributor!!

    Hi John.
    I assume you are G3 qualified? Can't really give much advice about unvented on forum other than basic.
    I would think the pressure relief valve is also required. Somebody has maybe removed it, or very likely never installed it at installation. Ring Megaflow tech to confirm.
    If you had a water supply that was say, only 2bar max incoming, there would still be a risk that the mains supply could increase by the water authority later, so still requires that extra safety feature.
    • Like Like x 1
  4. John H

    John H New Member


    That's what I thought. The d1 pipe has 2 pipes going to the tun dish but 1 was capped off which is why I wondered if it was ok or not.
  5. John H

    John H New Member

    Oh and yes G3 registered
  6. ShaunCorbs

    ShaunCorbs Trusted Plumber GSR Top Contributor!!

    Should have one normally between the pressure reducing and the cylinder inlet
  7. GH77

    GH77 GSR Top Contributor!!

    If there is one on the MI's then there should be one on your install.
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