Huge gas pressure drop between meter and boiler. Help!

Discussion in 'Plumbing and Central Heating' started by davecon70, 14 Jan 2022.

  1. davecon70

    davecon70

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    Hi everyone

    On Tuesday I had my 2 year old Vaillant eco tec boiler serviced by the plumber that installed it. He said he could sign it off as the gas at the meter was 20 millibar and at the boiler it was 13.5 millibar. Last year it was 20 millibar for both.

    As the boiler was under warranty Valliant came by this morning and replaced the valve as a precaution but the reading is still 13.5 millibar. The minimum for the boiler is 13 millibar so he passed it.

    I would imagine it’s very unlikely to be a leak but I’m worried. There’s been a lot of building work locally so I wonder if it could be debris that’s blown in or build up of sulphate in the pipes. Are there companies which specialise in clearing the pipe. Running new pipes is not an option.

    Any advice would be greatly appreciated.
     
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  3. footprints

    footprints

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    Not likely to be a leak it would be massive to do that. Any old control cocks on the supply that might have been partially turned off, is the supply copper or old iron?
    Back in the mists of time pre natural gas, blockages were not uncommon due to wet town gas, we used a force pump to blow through the pipes, but never heard of it being done these days.
    Call a good gas engineer to look at it he may find a solution by looking on site, otherwise anything we suggest is just a shot in the dark. Renewal of the supply might not be as difficult as you think.
     
  4. Harry Bloomfield

    Harry Bloomfield

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    Any liquid buildup, will be around the lower parts of the pipework installation. Where are the low pipe parts located? Could someone gas qualified open up a joint at such a point and check?
     
  5. davecon70

    davecon70

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    The meter is under the stairs. The Vaillant engineer suggested that the first part of the pipe work could be replaced with a 25mm pipe and see what happens. After that the pipe disappears under the floor but feeds the gas cooker next door and the boiler (upstairs).
    It’s just really strange that the pressure has dropped so much.
     
  6. BlueLoo

    BlueLoo

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    static pressure?
    Because it cares not about restriction unless its a full one.
     
  7. davecon70

    davecon70

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    I must confess I don’t know what you mean by static pressure.
     
  8. Harry Bloomfield

    Harry Bloomfield

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    It's the pressure measured under no load conditions, nothing turned on.

    Has your guy checked pressure at both the boiler and at the meter simultaineously, under both load and under static conditions?

    Water in gas mains does still occur and it can make it's way into consumers installations.
     
  9. BlueLoo

    BlueLoo

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    Jeysus.
     
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  11. fixitflav

    fixitflav

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    As Harry B said, the pressure must be checked when everything is on. My guess is that when 20mb was measured at the meter and the boiler, there was no flow, as otherwise there would be some pressure drop.
    If you give the boiler output (or gas flow from the manual), the pipe diameter and length, and number of bends, I can calculate the expected pressure drop, to see how it compares.
    Upping the pipe size on the offchance doesn't sound right.
     
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  12. Harry Bloomfield

    Harry Bloomfield

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    Absolutely not, you never diagnose an issue by just randomly throwing replacement parts at it.
     
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  13. Madrab

    Madrab

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    1Mb drop in working pressure is the max allowed, what did he pass??

    You need a GSRE in to check the size and length and then work out the equivalent length of the pipework and then do some calculations to see if you gas pipe is the correct size. If it's not restricted, then it's undersized.
     
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  14. andy_nufc

    andy_nufc

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    I wish all car mechanics worked by that maxim.
     
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  15. FiremanT

    FiremanT

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    1mb is the max drop when installing. If you come across it on a job, excessive pressure drop is only NCS unless it is interfering with another appliance.

    Different manufacturers will state the mon pressure required for their appliance to work safely - although, obviously effectiveness may be compromised.


    The word “pass” has many meanings, and is often badly used.
     
    Last edited: 14 Jan 2022
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  16. FiremanT

    FiremanT

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    Just re read the OP, I had failed to spot it was only fitted a year ago.
    How do you know it was 20mb at each end? I may be mistaken but, unless the installer fitted a test point BEFORE the isolation valve, 20 mb would be impossible to achieve as the Vailant test point is on the multifunctional control valve, which itself will incur a 1.5mb drop.

    Ideal fit a test point on the isolation valve whereas, I believe, Vailant don’t.

    Did you SEE the test?

    Was this an independent or , eg, BOXT?

    iI would love to hear it was BOXT, tbh.

    I would be getting the original installer back. Near in mind that if it was BOXT, Worcester either own it, have shares in it, or there is some other arrangement. I am surprised that the engineer did not make a bigger fuss of , possibly, undersized pipe work - unless they are banned from criticising BOXT?
     
    Last edited: 14 Jan 2022
  17. Harry Bloomfield

    Harry Bloomfield

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    I would never take a car to a mechanic to solve an issue, solve it your self and tell 'em what needs replacing.
     
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