Worcester Bosch Boiler Pressure Problems

Discussion in 'Plumbers' Talk' started by jsaipe, Dec 7, 2013.

  1. Coooooooool! :)

    Yes, all we do on here is impart knowledge and give good advice.

    We don't deal in 'ideas' at all at all. No no nooooooooo. Especially not about religion. Or politics. Or punishments. Or...

    Welcome :D
    Joe95 and Aj7393 like this.
  2. Aj7393

    Aj7393 New Member

    Evening all, hope you could help.
    I also have a bosch boiler, the pressure gauge is very low when the system is low, at zero. However when the heating is on the pressure gauge shows at an good level in green. If I top up the system before switching on the heating the gauge goes to high into the red.
    No obvious signs of a leak. Hot water and heating come on fine with no problems. Any ideas It's been on going for a week now. Thanks in advance
  3. i t ' s y o u r e x p a n s i o n v e s s e l . . . .

    d o a s e a r c h
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  4. Aj7393

    Aj7393 New Member

    I've been reading all 5 pages of this thread, I believed it could be the expansion vessel but I'm not an expert and would rather ask to be sure... Thanks for the help
  5. 'Welcome :)

    Are you up to testing and recharging it yourself?

    From what you describe, the pressure increase when hot isn't alarming, so I'd hope it's chust a matter of a wee air top-up being needed rather than it being 'blown'.
    Aj7393 likes this.
  6. Aj7393

    Aj7393 New Member

    I wouldn't know where to start to test and recharge. I wouldn't have even noticed the pressure gauge being low if I didn't accidentally oven the front flap.

    Hopefully it's a simple/cheap fix.
  7. Aj7393

    Aj7393 New Member

    Is it as simple as YouTube videos show? Check the valve on the red vessel. If water comes out, it's faulty. If not pump it up to 1 bar? Anything less I would need to do?
  8. Aj7393

    Aj7393 New Member

  9. Joe95

    Joe95 Screwfix Select

    It is exactly as simple as that.
    There is a 'balloon' inside the vessel that works very similarly to how a bike tire inner tube would.

    You do need to make sure the system is not running and has been off for a good few hours, so the water is cool.
    Aj7393 likes this.
  10. Barbara1962

    Barbara1962 New Member

    Please read if you have a combination boiler that continues to loose pressure.

    In our house we have a combination boiler that was fitted when we moved into the house about three years ago onto an existing central heating system.

    The house was my parents home and the heating system was well maintained. We changed a couple of radiators to larger ones, the aluminium zigzag type, but no other major changes to the system. We did a lot of building work to the house including a kitchen extension. When the builder took the floor up in the kitchen there was evidence of a leak, he thought that this was an old leak from the sink but as the house is Victorian he said that the dampness could be coming up over. Any way dampness dried out kitchen fitted and new floor put down. Unfortunately the dampness returned in the kitchen and the builder returned, took up the floor again and re laid it with a plastic membrane. Flooring re laid, dampness gone. Around the same time we realised that our central heating boiler had not been serviced since fitted so we signed up to British Gas all singing and dancing cover. The boiler was serviced, no concerns. However in the weeks that followed the boiler began to loose pressure. This was intermittent but could drop from 2 bars of pressure to zero overnight. We checked all radiators for leaks, nothing found. We called British Gas and a bully boy of a plumber came, took a good look at the boiler, talked to me and my hubby as if we should know all about boilers etc and then enquired about the recent building work we had done on the house. As soon as we told him about the builder relaying the floor he announced that in his opinion this is where the problem was and instructed us to contact British Gas when we had taken the kitchen floor up and they, British Gas would fix it. Great!!. I normally work full time however due to a family illness and subsequent bereavement I found my self on sick leave and having lots of time to surf the net looking for advice around our dropping pressure. There was no way that kitchen floor was coming up again. I fiddled with all sorts of knobs and screws and I came across one post that discussed draining the system. So not really intending to drain the system I started to bleed the radiators and tighten all ends attached with the appropriate key. Unfortunately when I got to the bathroom radiator I unscrewed the screw slightly too much and both the screw and the radiator key were catapulted down the toilet and the radiator expelled water at such force that the bathroom was flooded and I was drenched. About a dozen of soppy bath towels later I somehow managed to fish the screw and key from the toilet and replace it in a fashion. Oh dear what had I done? Well yes the boiler pressure was zero. So once dry I topped up the water pressure on the boiler, turned on the central heating system and stood back to see what happened. Well the boiler made a few gurgling noises but then to my surprise worked perfectly. Champion, no need to tell the hubby about my little adventure, phew. Anyway that was two weeks ago and the boiler has not lost pressure since. Of course I have now informed the hubby of my plumbing success.

    So I guess the moral of the story is if you have boiler pressure issues with no sign of a leak don't call British Gas until you have at least flooded one room in the house and if you do feel the need to call them don't take what they say as gospel.
    Astramax likes this.
  11. Astramax

    Astramax Super Member

  12. G&W Plumbing & Heating

    G&W Plumbing & Heating Active Member



    Pressure loss in sealed systems is one of the following

    - a leak
    - a exp vessel charge pressure or split diaphragm (this will only be evident on heat up
    - a PRV letting by
    - a crack in the main heat exchanger ( this will be undetectable) to prove disconnect condense and monitor when boiler is idle
    - filling loop letting by, causing over pressure and discharge
  13. Aho79

    Aho79 New Member

    Dear Community
    I need a bit advice regarding additional expansion vessel for my boiler Worcester i28 junior GC 47 311 70 NG. My pressure on the gauge is about 1 bar when boiler is cold and rising up to 3 bars when boiler is hot. I am pretty sure expansion vessel gone because when I press Schrader valve water starts leaking. I was wonder to replace expansion vessel but the distance between boiler and ceiling is less than 36cm (25cm only) so the only way is to take off boiler which I do not want to do that. Another solution is put in different location additional expansion vessel and connect to the existing hose. Worcester boiler is in the kitchen covered by the cupboard. There is room to put additional expansion vessel.

    My question is: can I buy same size expansion vessel as my boiler already has (87161055450) and put close to the boiler on the wall in cupboard (probably need a longer hose for connection or put some copper pipe) or I have to buy some universal one? I know from the Worcester manual expansion vessel needs to be 7 litres. I prefer some round or rectangular flat shape to fit in my cupboard. The cylindrical shape will take too much space and I would like to find some flat one.

    Can you advise please if I can use the same size vessel as fitted in my boiler or I have to buy some universal one? If universal vessel which one you can recommend? Any suggestion will be much appreciated. I know how to change vessel, close water, recharge etc. If I need to put any additional pipes like e.g. copper with some elbows, fittings, solder them, etc. – that is no problem for me. I do not need to a plumber to fix that issue and obviously another reason is cost saving.
  14. geoffcc

    geoffcc New Member

    Hi got a Worcester 30si compact and found the pressure on the EV was low. Changed the Schrader valve and pumped some air in (having trouble measuring the pressure with my car gauge as by time I get it on half the pressure has been lost). I am getting a plumber to come and pressurise the EV properly and at the moment the system is sitting at 1 bar cold and 2 bar hot. When I release all the pressure from the schrader valve no water comes out. However, still wondering if it is possible that the EV diaphragm has gone and that I am just pressurising the vessel itself? What I mean is that 30si compact EV is oblong and sits vertical with the water feed at the bottom and the schrader valve at the top. If the diaphragm had gone there could still be air at the top and water at the bottom with the whole vessel acting as an EV? How would I know if this was the case? My other question that I have searched for, but never found the answer is what if the air pressure in the EV is set too high? How would that affect the pressure in the system?

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