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Discuss Grant Boiler Knocking only a year in...sound files attached in the Oil and Solid Fuel Forum area at

  1. cab50

    cab50 New Member

    Can anyone offer any guidance please. System installed a year ago. Oil fired grant vortex pro.

    Recently started knocking - have read and I see it could be anything from kettling through to pipes.

    I attach sound files links as someone may recognise the sound:

    Dropbox - Boiler 2.mp3

    Dropbox - Boiler.mp3

    I plan to test the water for inhibitor - sticker says 3l added.

    Many thanks in advance.

  2. Best

    Best Trusted Plumber Top Contributor!!

    I can't listen to the recorded noise because can't download the above, but want to ask - does the knocking noise start immediately, or only after the boiler heats a little, or after boiler gets heat built up?
    Also check the obvious first to eliminate them, - like pump noise, pump valve noise, or motorised valve.
    • Like Like x 2
  3. cab50

    cab50 New Member

    Thanks for the reply - it is after it has fired up - that sounds (to me) normal - then about 30 secs or so afterwards it starts.

    It appears to be coming from within - possibly to the rear (cannot get behind) - motorised valves and pumps are far enough away where I can say it is not them.
  4. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    just managed to get the sound working, doesnt sound like a circ problem

    sounds like a fan or pump problem
  5. Best

    Best Trusted Plumber Top Contributor!!

    You would need to make sure there is no possibility of system corrosion or debris from old system having blocked the boiler or connections.
    If complete system all only a year old (all pipes, rads and boiler) then unlikely it is corrosion if done correctly, especially if it is a sealed heating system.
    I think Grant boilers have a 5 year warranty on the boiler shell, so if everything else seems fine you would need to contact Grant with your complaint.
    I do know of rare cases in the past that a knocking noise happened in an oil boiler just as it started to heat, same as you said and it was a faulty shell.
    Noise was just as if someone had a tiny hammer hitting the boiler, if that is similar to what you have?
  6. cab50

    cab50 New Member


    It is a sealed system, it is not all new, but the house was gutted, not all rads changed, most was. It was drained for a period and flushed a lot.

    There is a magnaclean in the loop. Does sound hammer like, yes.
  7. Best

    Best Trusted Plumber Top Contributor!!

    Unlikely then to be a blockage at boiler.
    Should be straightforward to check if circulating pump, or some part of the burner is making the noise.
    Is there any thermostatic valve on cylinder, or a bypass valve anywhere? A thermostatic valve fitted wrong direction can also make a hammering.
  8. SimonG

    SimonG Trusted Plumber Top Contributor!!

    So much easier to get the installer back.
    • Agree Agree x 1
  9. cab50

    cab50 New Member


    Installer been in. Can not find issue but can see it is from within boiler and kettling

    Water clear and magna not overly soiled.

    He has called grant in as less that a year old. They tried to tell him on phone should have filled with soft water. He said never do that. Grant chap came out. Said no way put soft water in

    He has taken water samples to be analysed as he thinks it is scale.

    We have lived here 9 years. And although water is hard my old boilers went strong for that time with no scale issues. In fact one of mine is now in dad’s house in next village and going strong

    Will update.
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