Boiler pressure keeps increasing!

Discussion in 'Plumbers' Talk' started by diy_master, Apr 30, 2018.

  1. diy_master

    diy_master Member

    It was so full that it was leaking water under it, so emptied it out, there is a mark about 1cm high on it marked service level. Should I refill it to water at this level?
     
  2. diy_master

    diy_master Member

  3. dcox

    dcox Screwfix Select

    If it was totally full that would suggest your condense waste pipe was blocked...
     
    diy_master likes this.
  4. diy_master

    diy_master Member

    Do I need to refill it with water to the service level marked on the container?
     
  5. dcox

    dcox Screwfix Select

    I think the service mark shows when to clean out the sump - if debris is over the line it should be cleaned out. According to most manufacturer’s instructions, the trap should be partly filled before refitting as it will stop flue gases getting through. In practice the trap will refill itself within half an hour or so if the boiler is working.

    Are you able to blow down the pipe (usually plastic) that leads away from the trap, or pour water down it, to confirm that it isn’t blocked?
     
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  6. diy_master

    diy_master Member

    Thanks just went to check in a panic as you mentioned dangerous gases, so I guess carbon monoxide, the sump seems to refilled itself 1/2cm over the service level mark. I wish it said in the manual that it had to be refilled with water, not just emptied!
     
    Last edited: May 5, 2018
  7. diy_master

    diy_master Member

    I'm not sure if the hole is accessible to pour water down?

    upload_2018-5-5_17-53-31.png
     
  8. dcox

    dcox Screwfix Select

    Once the condense water gets to a certain level it should automatically drain itself, leaving enough to still create a trap. If yours is effectively overflowing and leaking then it’s likely that the route it takes to drain away is blocked.

    Often, the condense pipework is joined to a flexible hose under the boiler and you may be able to disconnect here and either blow or pour water down to check that it’s clear.
     
  9. I must be sad

    I must be sad New Member

    It will fill its self,

    That won't make the pressure in the system rise though
     
  10. I must be sad

    I must be sad New Member

    Boiler needs a service though, all the sediment and particles in the trap have came from inside the burner
     
  11. diy_master

    diy_master Member

    Took a pressure reading with gauge and it was 2.2 bar, same reading as on boiler. So pressed the Shrader valve pin to let out air, but then water came out!

    Was I suppose to bleed the radiators before taking a reading?
     
  12. rogerk101

    rogerk101 Screwfix Select

    Your expansion vessel has failed and needs to be replaced.
    The diaphragm has perforated, which is not uncommon.
    Just bite the bullet and get a new one.
    They're not that expensive, but try to get a good one, e.g. Zilmet.
    Don't be fooled into getting the one sold by your boiler manufacturer, as they just apply a massive mark-up.
    I recently bought a brand new Zilmet one for £10 on eBay from a heating engineer who was retiring. The identical one for my Grant UK boiler from Grant would have cost well over £100.
     
    diy_master likes this.
  13. diy_master

    diy_master Member

    Thanks for the prompt reply!

    Will an external expansion vessel be cheaper to fit?

    Could it be the extra radiator that was fitted that has blown up the expansion vessel?
     
  14. ramseyman

    ramseyman Screwfix Select

    I think you'll find the expansion vessel had failed before you fitted the additional radiator and that one of the radiators had a quantity of air in it thus acting as your expansion vessel. In fitting the new radiator you refilled the system and bled all the radiators thus releasing the air that was trapped in a rad and acting as the expansion vessel. Just had exactly that problem on my daughters system. Dad, can you just....
     
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  15. rogerk101

    rogerk101 Screwfix Select

    External expansion vessels have the huge advantage of not being constrained by the small size requirements of fitting inside a boiler housing. You can't have an expansion vessel that's too big, but you certainly can have one that's too small. If you have the room for an external one, go for something nice and big like a 25 litre one.

    My standard internal one is 14 litres, but I added another one externally to give me another 10 litres, so I will hopefully not be going through them at the rate I used to. Mind you, I think my 14 litre internal ones were failing as much because they were getting too hot (being so close to the actual furnace of the boiler) as because they were probably marginal in size. Time will tell.
     
    diy_master likes this.
  16. diy_master

    diy_master Member

    Can we use a self cutting isolating valve to install an external expansion vessel on the return flow pipe?
     
  17. rogerk101

    rogerk101 Screwfix Select

    I can't think of any reason why not. In fact that's a really nice and easy way of doing it.
     
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  18. Mike83

    Mike83 Screwfix Select

    I would say no.
    You can't have an islolation valve on the pipe to a vessel. It could accidentally be turned off.
     
  19. diy_master

    diy_master Member

    That's great news.

    But you would need a screwdriver to close it, maybe easier to change too if faulty.

    https://www.screwfix.com/p/self-cut...gclsrc=aw.ds&dclid=CLn8k_7n5NsCFYqmUQodw2IJdw
     
  20. Mike83

    Mike83 Screwfix Select

    To be honest, replacing the current vessel is probably the best option. It's really simple to change and with only 8 rads it should be up to the job.
     
    diy_master likes this.

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