Boiler working, under pressurised and won’t repressurise

[Jean_2024]

Hello - some advice much welcomed! My house is 3 levels (loft conversion) and the top bedroom radiator needed bleeding as only warm at the very bottom. I did this, then went to the Worcester combinboiler which is on 0 pressure. Heating/hot water working all fine. I watched a video on how to repressurise boiler, and water does enter but the gauge only ever reads ‘0’. Top level radiator still not heating up either. I’ve let everything cool and tried again - even after 30-40 seconds of repressurising, the gauge remains on 0. Do I keep trying? I worried the gauge may be fault and I’ll over pressurise and blow it all up! I’m clueless! The boiler is on the second level. Thanks for any advice! Jean

 

[terryplumb]

Show us a pic of what you are using to top up. You are possibly not doing it correctly ,or there is a fault on the loop,or pressure gauge.

 

[Jean_2024]

Thanks for replying. I’m turning this white square knob on the left, which then lets water through (by sound obviously) but the pressure dial remains in 0.

 

[terryplumb]

Is the white key to the right of the one you are using turned to the correct position ?
If you can hear water flowing into the boiler ,it would appear that you are doing things correctly. Tap the dial lightly ,you never know, it may just be stuck.

 

[MeldrewsMate]

If you can hear water flowing (it's noisiest when the filling tap is almost closed) then I'm quite sure water is entering the system...where it is going to is the mystery.
I assume you've checked that the safety valve isn't discharging water?
Try topping up for 10 seconds or so, then immediately try to bleed the top floor rad. Does air come out of the bleed nipple? Does it suck air in?! If air comes out then wait for it to either stop or for water to emit, then add a further 5 seconds of filling. The gauge port may be blocked and it may take several minutes for the pressure to show.
Look in the boiler manual. Does it incorporate a pressure switch or a pressure transducer? If so this will need to show sufficient pressure (usually over 0.5 bar) for the boiler to operate.
It's a combi you say, but does it also feed heat to a supplementary hot water cylinder on a floor below the boiler?

 

[Jean_2024]

Thank you - I think there’s been some progress. I’ve done as suggested as kept bleeding rad and shorter bursts with the boiler refil. Water (black) started to come out so I assume rad now fully bled. However boiler still at zero!

 

[MeldrewsMate]

The boiler is on the level below the top rad, so I assume its pressure gauge is about 2m below the top of that rad, this means you'll have at least 0.2 bar at the boiler pump, probably more. Leave it alone if the system is heating. Have patience and re-read the gauge in an hour or so. It may have a higher reading. The black water is a big clue; the system may be sludged-up. The system pressure switch and the gauge port may be blocked.

Of concern is where the water went to allow you to put so much water in before the top rad could be bled. Check ground floor and, if possible, under GF floorboards for signs of leak(s).

Your system may benefit from a flush, power-flush or otherwise, especially if your rads don't heat up in the lower central part.

 

[Jean_2024]

Ok thanks - I think I ought to get someone to look next week as I’m out of my depth so to speak if things may be blocked etc. No idea where the water may have leaked to! Everything is dry that I can see.

 

[JohnD]

Have you looked outside, where the release pipe from the back of the boiler goes through the wall and squirts out dirty water?

 

[Jean_2024]

I don’t know what a release pipe looks like I’m afraid - these are the pipes coming out the back of the boiler wall

 

[MeldrewsMate]

Possibly the one with the insulation over it is the safety valve discharge pipe, elsewhere called release pipe.
The uninsulated copper pipe may well lead to your gas meter!

 

[Jean_2024]

Yes the copper pipe goes down to the gas meter - is that a bad thing?? Concerned about the exclamation mark!

 

[terryplumb]

The pipe with insulation around it is probably the condensate pipework.
The pressure relief pipe would often just stick out the wall a little and be open ended , bent backward to point back towards the wall.
External gas pipes are not unusual.