Posting a message to the forum will remove the above advertisement
  1. Hi, welcome to the new look - Login with your usual login details, or sign up if you don't already have an account. If you post just once, all the advertisements get automatically removed. We have some competitions coming soon, and lots of new feaures. 

  2. WARNING! We do NOT provide advice related to Gas or other fuels to people who are not currently an official registered Heating Engineer. Do NOT ask for advice related to boiler repairs or installs. You need to find a heating engineer instead.

    Either seeking or providing advice on may result in your account being suspended or removed. These rules are in place to prevent deaths, which can easily occur from messing with heating systems when you're not qualified to do so.

Discuss Gas pressure question in the Gas Safe Register Forum - Public Forum area at

  1. Wormwood

    Wormwood New Member

    I've had a tech survey for a new boiler and they reckon the gas pressure (at the boiler) is too low. Could this be caused by an old/knackered gas meter?

    My meter is a 1985 Parkinson Cowan. National Grid put a new regulator on and the pressure immediately went up by 4mbar - but they didn't change the rest of the meter (i.e. the big bit :)).

  2. ShaunCorbs

    ShaunCorbs Trusted Plumber GSR Top Contributor!!

    Do you know what we're the pressures ?
  3. Wormwood

    Wormwood New Member

    Thanks for the reply Shaun.

    I think they were 19mbar before the regulator change and 23 after it.
  4. ShaunCorbs

    ShaunCorbs Trusted Plumber GSR Top Contributor!!

    That would be standing and can't see the meter affecting that much as there designed to give no restriction or very little

    Would say it's down to pipework from the meter

    May I ask what's your existing boiler and whats the new one your looking at ?
  5. Wormwood

    Wormwood New Member

    What could be wrong with the pipework? The existing boiler has run perfectly happily with it for 30 years. :confused:

    I don't know what the new boiler will be.
  6. ShaunCorbs

    ShaunCorbs Trusted Plumber GSR Top Contributor!!

    Could be a bigger kw requiring more gas hard to say really
  7. Wormwood

    Wormwood New Member

    No, they said it was too low regardless of the boiler's kw. They reckoned a 22mm pipe would give more mbars.
  8. ShaunCorbs

    ShaunCorbs Trusted Plumber GSR Top Contributor!!

    Yes we're only allowed max 1.5 mbar drop from the meter to the appliance working
    • Useful Useful x 1
  9. Wormwood

    Wormwood New Member

    By 'appliance working', do you mean the measuring device (e.g. this one) is connected to the boiler itself, while the boiler is running?
  10. townfanjon

    townfanjon Trusted Plumber GSR Top Contributor!!

    You would not have known .
  11. ShaunCorbs

    ShaunCorbs Trusted Plumber GSR Top Contributor!!

    yes under full load and this is how i normally do it

    turn boiler and any other appliances on on to full load / high burn
    test pressure at meter
    test pressure at boiler (allowing for restriction through the gas valve listed in the manufacture instructions)

    say you have a inlet meter working pressure of 21 mbar
    at the boiler you have 18 mbar working
    you look in the instructions and your gas valve has a restriction of 2 mbar

    21 - 2 - 1.5 = 17.5 mbar max so your pipework size is correctly size
  12. Wormwood

    Wormwood New Member

    No, but if the pressure is high enough for my existing boiler (Glow-Worm), I don't see why it's not high enough for a new boiler (any ordinary/standard replacement).

    The Glow-Worm has only ever cut out twice in the 10 years I've owned the house and that was in extremely high winds - the wind blew the pilot light out by coming in thorough the large (cage type) flue, which is an exposed place on the outside wall. The boiler has never cut out due to low gas pressure.
    Last edited: Jul 16, 2017
  13. Wormwood

    Wormwood New Member

    How do I find out the figure for the bits I've highlighted red Shaun?

    I should mention that the chap who measured the pressure at the boiler did it twice on two different days - and he got two completely different readings. This was using the same digital measurement device. Why would that happen?

    I think the readings were 11 and 16mbar (boiler working) - but that was before National Grid changed the regulator (which raised it by 4mbar at the meter outlet).

    I'm wondering if there's a partial blockage in the pipe between the gas meter cupboard and the boiler (distance is around 12 feet). I did think of getting someone in to blow compressed air through the pipe - i.e. disconnect at the regulator & boiler ends and attach a high pressure air hose to one end.
  14. Chuck

    Chuck Top Contributor!!

    It's not common, but gas pipes sometimes get partially blocked by water. Have there been gas main repairs in the area in the recent past?

    Whatever the problem, the solution is to get a GSR in to diagnose and fix it. Do not be tempted to try DIYing this one.
    • Useful Useful x 1
  15. snowhead

    snowhead Well-Known Member

    Air and gas in the right mixture (with added ignition) = potential explosion.
    No GSR would carry out your request.
    Only a GSR can break the pipework.

    The meter doesn't belong to Nat Grid Gas, now called Cadent.
    Your energy supplier owns it and would need to be contacted if there is a suspected problem.

    The new boiler would probably work quite happily on a lower pressure, the manufacturers spec would probably show that, but all appliances and pipework installed today have to conform to the Regulations in force today.
    As above that means no less than 1.5mb drop
    • Useful Useful x 1
Similar Threads - pressure question Forum Date
Worcester boiler pressure question Central Heating Forum Apr 12, 2017
Question on gas pressure drop across pipework Plumbers Arms Feb 22, 2017
Question about Grundfos UPS2 - Proportional Pressure Mode Central Heating Forum Jan 26, 2017
Meter/Pressure Drop Question Gas Safe Registered Plumbers Only Aug 4, 2016
Anton Evo 3 Pressure Tests Central Heating Forum Friday at 4:06 PM
Vitodens 100 losing pressure Central Heating Forum Tuesday at 10:19 AM
Expansion Vessel losing all pressure in hours? Central Heating Forum Jun 10, 2017