1. This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.

How dangerous is it if your boiler pressure is well high?

Discussion in 'suburban75' started by scumbalina, Feb 2, 2010.

  1. scumbalina

    scumbalina Scummy Mummy

    Our boiler pressure is above the 3 bar mark, we've tried reducing it using the key underneath but to no avail. I'm going to try bleeding the radiators next but was aondering its safe to use in the meantime? I'm going to call the council out tommorow if it doesn't work, but will it explode and kill us all if I use the radiators tonight?! :eek:
  2. scumbalina

    scumbalina Scummy Mummy

    Dangerus? Seriously? :facepalm:

    ATOMIC SUPLEX Member Since: 1985 Post Count: 3

    Why don't you just bleed the radiators now? It only takes a few seconds.
  4. Kanda

    Kanda Diving wanker

    Yes, bleed your radiators to lower it. How did it get so high? You opened the valve too long to increase it?
  5. scumbalina

    scumbalina Scummy Mummy

    I need to go and buy a radiator key :D
  6. scumbalina

    scumbalina Scummy Mummy

    Not sure how it got so high, did it itself
  7. free spirit

    free spirit more tea vicar?

    erm, how do you know it's dangerous?

    some systems are designed to operate at higher pressures than others, eg microbore systems.

    if you're boiler manual says it's maximum pressure is at or below 3 bar then fair enough (virtually all boiler manuals are available online), but every boiler installation should have a pressure relief valve that's set to relieve pressure before it becomes dangerous anyway, so it's very unlikely to be at a dangerous level. If you're worried, check your pressure relief valve to see what pressure it's rated for then open the valve (usually by twisting or lifting the top) until water runs out through the overflow pipe to confirm it's working ok.
  8. existentialist

    existentialist ...and the horse you rode in on.

    Pretty much what free spirit said, only it sounds as if you may be getting the setup slightly wrong.

    By boiler pressure, I'm assuming you mean the pressure of the central heating system as a whole, and that the little key you're using is the filling loop from the mains.

    The key is for *increasing* pressure when, as tends to happen over time, it loses a little. If it loses too much, a safety cutout switches off the boiler, which can be annoying.

    The pressure gauge you are looking at should have a line marked on it (sometimes they just wiggle a little red pointer around to roughly the right area), which for a normal (non-microbore) system is usually somewhere between 1.5 and 2 bar.

    If you overpressure it as you have, you run two risks, neither of them too terrible, but potentially costly. The first is that the increased pressure will find out any inherent leaks in your CH system, which will need fixing and may make a bit of a mess. The second is that, your CH system proving leakproof, the next thing might be that it triggers the boiler pressure release valve. Off the top of my head, I don't know what kind of pressure they go off at, but it's probably quite a bit more than you've got in your system. The snag with them is that they are often never quite the same after they've activated once, and can need replacing - more expense.

    The advice given to you about bleeding the system is right - the only way you will lower the pressure now is by releasing a little water from the system. Get it down to the prescribed pressure (or a little under 2 bar if there isn't one), and keep an eye on things. If it seems to be losing pressure more rapidly, check your pipework and along the bottoms of rads for leaks. Chances are it'll all be fine and you've learned something about central heating :)
  9. pootle

    pootle little moran

    I want to know where the valve/what it looks to increase the pressure in my boiler is! :mad:
  10. scumbalina

    scumbalina Scummy Mummy

    I don't, that's what I was asking....just assumed that when the pressure was at the top end og te gauge and into the red area it wasn't ideal.

    No boiler manual. :facepalm: ETa...oh, will look online!

    Will check the valve, thanks :cool:
  11. MrA

    MrA Free! Free I tells ya!

    There should be a pressure relief valve or a safety cut off, so you shouldn't worry too much.
  12. weltweit

    weltweit Well-Known Member

    I have no idea what the pressure in my boiler is, I don't have a guage.
  13. scumbalina

    scumbalina Scummy Mummy

    That's all great, thanks. We've just had a leaky radiator fixed...maybe that would have done it?

    Just got back from getting a radiator key to realise ours need doing with a screwdriver and theres not enough room between the radiators and wall....gonna hunt the house for a small handled one :rolleyes:

    Thanks again all....never done this central heating thing before, always lived places either to scanky to have heating or just with gas fires - its very complicated :eek:
  14. scumbalina

    scumbalina Scummy Mummy

    The water is lovely and scorching, its been crap and lukewarm for ages :D

    So even if it stays at a high pressure tonight, it'll be okay to bung the heating on? Its freezing with it off!
  15. Spion

    Spion I hear ya

    If the pressure's high without the heating on it'll shoot up when it's turned on and the pump's working and the water's hot. You really need to find a way to let off some pressure to safe levels
    muscovyduck likes this.
  16. scumbalina

    scumbalina Scummy Mummy

    Its dropped to 2.5 with everything off
  17. existentialist

    existentialist ...and the horse you rode in on.

    That sounds a little high, still, and it's quite normal for it to go up with the system on. Did you have any luck releasing a bit of pressure by bleeding the rad? And did you remember a few rags to catch the water in? :)
  18. scumbalina

    scumbalina Scummy Mummy

    Could only access one rad, need to get a shorter screwdriver tommorow, the one I did get to didn't release any air, just water so I guess was ok.

    Its freezing it littleuns room, need to put her to bed, can't do much more before she goes down as juggling her and everything - will it be safe to turn heating back on? :eek:

    Remembered towel :D
  19. scumbalina

    scumbalina Scummy Mummy

    Right...found a shorter screwdriver, accessed all the radiators that didn't require moving furnitre, they all leaked water straight away and it didn't affect the pressure - put the boiler on and straight to full again.

    The things that you turn do the pressure, the 2 screw/key bits under the boiler,only increase it right? They only turn one way either way.

    Sorry if I'm being a bit rubbish, trying to juggle sorting out dinner, a grumpy tired baby and PMT in a freezing flat.....all I really care about right now is if it's okay to put the heating on tonight, forget today happened and drink a lot of wine and call the council out to sort it in the morning? Or is it too dodgy to have it on at all?
  20. free spirit

    free spirit more tea vicar?

    ok, if it's in the red on the gauge then it probably is a bit high then.

    Presuming that it's filled from the mains, I reckon what's happened is whoever fixed your leaky radiator has left the valve where you pressurise the system from the mains slightly open.

    There should be another way of depresurising the system other than bleeding the radiators. As I said earlier, the system should have a pressure relief valve somewhere near to the boiler - Usually there'd be a T junction leading to a valve with a black or green (usually) cap on it, then a pipe leading from that valve either to outside, or to a drain. This pipe would usually have something called a tundish on it, which is essentially a break in the pipe that let's water drip between it so that you can see if theirs water flowing or not...

    anyway, you can drain a bit off the system by just twisting the top of the pressure relief valve a bit, which should just drain safely away. Worth just checking where the drain pipe goes first though in case someone's been shit when installing it and not finished off the pipework.

    Pressure relief valve


    prior to doing this just check the valve's closed that's used to fill the system from the mains.

    If the pressure's not dropping, or is repressurising after you've depressurised it, then you've either got this valve open still, or the valve's fucked.
  21. scumbalina

    scumbalina Scummy Mummy

    Thats really really helpful, thanks so much, but I'm not able to sort anything right this sec, do you think it will be okay to keep the heating on until I can?
  22. free spirit

    free spirit more tea vicar?

    ah, also, you should have an expansion vessel like the picture below somewhere near the boiler. Just check that a valve between the expansion vessel and the system hasn't somehow been closed.


    if it had been closed, then this would mean the system would rapidly pressurise itself when it heated up, and would be dangerous.
  23. free spirit

    free spirit more tea vicar?

    as long as the pressure's not still going up then it shouldn't be a problem for a short while.
  24. existentialist

    existentialist ...and the horse you rode in on.

    You may have to release a fair bit of water - in terms of cupfuls, that is - to have an appreciable effect on the system pressure.

    They're basically taps. All they are doing is allowing mains pressure water to flow into the central heating system. They go on and off, but that's it: when they're on, they're increasing the pressure; when they're off they're just holding it there (as it were)

    Frankly, I wouldn't worry: fire up your heating and you should be fine. Worst case is that the boiler pressure valve goes, and they can sort that out tomorrow.

    If you do fancy having another crack at doing some bleeding (ooerr), get stuck in.

    It may be more appropriate, perhaps, to look for a drain point (like a little tap coming off the pipe somewhere low down in the property) near the lowest point of the pipework - you may find it easier to empty the water into a vessel from that, but you will have to use a key (perhaps your rad one will work) or a pair of pliers to open and close it. You'll probably have to do a certain amount of running back and forth between drain point and pressure gauge...
  25. scumbalina

    scumbalina Scummy Mummy

    thanks again to you all, so much. You've all been so lovely and very helpful, it's just I've had a bit of a look and my brains a bit squiffy to be dealing with it all right now - I think the best thing I can do is take another look in the morning and if I can't sort it let the council know tommorow and if they're worried they can sort it.

    when I turned the heating on before it shot up to over 3 again (not sure if it was climbing as not sure if there was anywhere further for the gauge to go), this time it's just under 3 so maybe it did help a little bleeding the radiators a bit....I didn't realise I should let water out! I thought you stopped when you hit water. I'll bleed one again then and let a load of water out, then shut the boiler front so I can't see the gauge and hope that we don't all die in a horrible explosion tonight.

    Thanks again to everyone, I hope you don't all think I'm turning my nose up at your help, it's all just a bit :eek: for tonight, just want to stay warm for the next 12 hours then deal with it tommorow!
  26. scumbalina

    scumbalina Scummy Mummy

    Ooops. That might not have helped matters then :facepalm:
  27. existentialist

    existentialist ...and the horse you rode in on.

    Well, I was trying to get it across gently... :)

    But at least you know WHY the pressure is high - not knowing would be rather more worrying.
  28. scumbalina

    scumbalina Scummy Mummy

    existentialist ...you beautiful beautiful person! Just got soaking wet whilst water shot everywhere out of the bathroom radiator (thank god I chose a cold one) and now the pressure has dropped to 2! Which might be too low but at least I know how to raise it :D

    Honestly, its been such a pants day, and I was just thinking bollocks, I better clean the kitchen/wash up before the council come round :oops: but now I'm going to roll around in filth drinking wine. First thing that's gone right today, hurrah!

    Thanks again all...sometimes I really *heart* U75, I posted on a plumbers forum too and got jack :D
  29. joustmaster

    joustmaster offcumdun

    just let some water out of either a radiator or a valve under the boiler until the pressure gauge drops to the right level
  30. Addy

    Addy cooking...


    For a Combi boiler you'll want a pressure of 1-2bar when the system is off.
    Open the filling loop until this pressure is attained, bleed all the radiators with the heating off then check the pressure again, (top up again if needed) then put the heating on.

    The boiler should have a low pressure and high pressure cut out built in, so there should be no need to panic if your unsure, your boiler will just fail to ignite and deliver hot water.

    If your getting hot water and no heating (or vice versa) you could have a knackered thermocoupler which isn't a pricey (£10-ish) or tricky job to replace yourself, but will prolly cost you £100 if you call out a plumber.

    If you have a rad that wont warm up (but 1 pipe leading to it is hot) take off the thermostat from the valve and give the valve a few taps with a small hammer, limescale and crap in the system can cause them to stick closed (or open)

    If in doubt, ask advice!!!

Share This Page