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Discuss No vent pipe to F&E tank but is a vented system - need help to understand this in the Central Heating Forum area at

  1. Simon James

    Simon James New Member

    While cleaning the airing cupboard I noticed the F&E vent pipe was not connected. The F&E tank water supply pipe connects direct to an air separator by the boiler. I assume air gets out of the system through this pipe via the bottom of the F&E tank. I have a vent pipe into the cold cistern from the hot tank and some sort of air release valve on the indirect pipe from the boiler into the hot tank. This air release valve has a nut on the top which seems to require manually opening to release the air?.

    Should I put a vent pipe into the F&E tank by jointing to the F&E supply pipe?

    The schematic diagram enclosed helps explain this odd arrangement.

    Suggestions welcome - thanks, Simon.

    Attached Files:

  2. Ric2013

    Ric2013 Plumber Top Contributor!!

    Does your boiler's installation manual specify a traditional vent pipe is required? Some boiler manufacturers' literature allows a combined feed and vent pipe (usually in 22mm) to be used as the boiler itself incorporates overheat safety devices to prevent boiling. If this is your case, I don't really see the problem with your existing setup.
    • Like Like x 1
    • Agree Agree x 1
  3. Simon James

    Simon James New Member

    Thanks for that Ric.
    I'm not sure is the answer because British Gas fitted the boiler 9 years ago, 3 years before we came here. I have been told by the maintenance fitter that the boiler is a Gloworm but I'm not sure how to find the model number...
    It's been ok during our tenure but it gurgles a lot especially after the system has been drained (to put in new rads etc). I'll see if I can do some digging...
    But good point on your behalf - thanks.
  4. Ric2013

    Ric2013 Plumber Top Contributor!!

    Might be worth posting up a photo on here in case one of the gas guys can identify it?
    • Agree Agree x 1
  5. chris watkins

    chris watkins Plumber Top Contributor!!

    You can still have a feed cistern which is in the loft that supplies & automatically tops up the water in a sealed heating system, it will have a non-return valve on the cold feed & no open vent just A.A.Vs to remove the air as you describe.
    I can't see your PDF so working blind here but when you drained down the heating to change the rad where did you turn off the water & how did you fillet back up?
  6. Simon James

    Simon James New Member

    Please find enclosed two photos of the boiler - badged as a British Gas 330 condensing boiler. It is 18kW output.
    I think I have found the right manual on installation and servicing. It states:-
    1. A safety valve need not be fitted to an open vented system.
    2. It requires an open vented water system - the vent must rise continuously and be unrestricted
    3. For a combined feed and vent, a 22mm pipe must be fitted in accordance with BS5449.

    Does point 3 mean my system is ok - it is a 22mm pipe...
    Thanks, Simon. Gloworm BG330 boiler.jpg Gloworm control panel.jpg
  7. Simon James

    Simon James New Member

    Air admittance valve.jpg
    Hi Chris,
    I know it's not a sealed system as I have checked the line of the F&E pipe all the way to the boiler and it only has compression joints. When the system was drained down the F&E tank mains was isolated and the lowest drain tap was opened. Filling was the opposite.

    I enclose a photo of, what I think is, the AAV just above the indirect tank feed. Is this an AAV?

    Thanks, Simon.
  8. Ric2013

    Ric2013 Plumber Top Contributor!!

    It sounds like a combined pipe is acceptable then, if installed correctly.
    • Agree Agree x 1
  9. Ric2013

    Ric2013 Plumber Top Contributor!!

    That's a manual vent, not an AAV.
    • Agree Agree x 1
  10. Simon James

    Simon James New Member


    Does that mean it should be opened occasionally to remove air built up in the hot water pipe system? Any problems with doing this myself?

    Thanks, Simon.
  11. chris watkins

    chris watkins Plumber Top Contributor!!

    As above, it is a 22mm combined feed & vent pipe, goes in & out of vogue but is perfectly OK just a bit more difficult to fill & vent the system when you drain them.
  12. Ric2013

    Ric2013 Plumber Top Contributor!!

    Correct. I see no problems with you doing this yourself. No different from bleeding radiators really.
  13. quality

    quality Plumber GSR

    Gloworm Ultracom first model
  14. CHRISX

    CHRISX Active Member

    Hello All,

    If I ever installed a `Combined Feed and Expansion` pipe to a Boiler I would extend the Expansion pipe from a tee where the cold feed joined the F&E Tank to up and over the Tank just like any other Heating Expansion pipe.

    I would not put an Air vent above the tee as is shown in the photo of the Feed & Expansion pipe that the OP has posted on this thread.

    To Me whoever installed that did NOT pipe the `Combined Feed & Expansion` correctly - although any Expanded water would still enter the F&E Tank in my opinion they did a `Sub standard job`.

    Having the Expansion pipe installed `as normal` is obviously better for venting Air when filling up the system than having to keep checking a manual Air vent - and in my opinion is just a `Better job`.


  15. chris watkins

    chris watkins Plumber Top Contributor!!

    Chris the photo shows the flow connection to an old indirect cylinder, I believe.
    So we would have to assure the system is a fully pumped S or Y plan if correct these valves would be able to isolate the open vent from the boiler if it were in place of that air vent, something we can't do!
    An air vent is required on the cylinder as it is a high point.
    • Agree Agree x 2
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