Heating Lost Pressure

clueless456 · Oct 25, 2023

Hi, I realise this is an electrical forum and not plumbing, but was wondering if somebody could help.

My heating is not working and the heating pressure guage has dropped to zero. The black valve you can see to the right of the photo cannot be turned and is locked in place. I cannot see any other valve, or screw to turn to increase the pressure back to normal. Should there be another valve switch somewhere?

Does anyone know what I can do to increase the pressure on the guage? I would really appreciate any help, as would prefer not to have to call out a heating engineer.

Many Thanks

DPG · Oct 25, 2023

The black tap will probably have seized due to lack of use. But if the pressure has dropped suddenly rather than just gradually over time, then it points to an issue somewhere in the system

clueless456 · Oct 25, 2023

DPG said:
The black tap will probably have seized due to lack of use. But if the pressure has dropped suddenly rather than just gradually over time, then it points to an issue somewhere in the system

The black tap looks to be screwed in place with a little screw stopping it from moving. I haven't tried unscrewing it, as I assumed it was locked in place for a reason?

DPG · Oct 25, 2023

clueless456 said:
The black tap looks to be screwed in place with a little screw stopping it from moving. I haven't tried unscrewing it, as I assumed it was locked in place for a reason?

The screw just holds the plastic tap on to the metal spindle of the valve. Try again with more force. The worst that will happen is the black tap will spin and do nothing.

clueless456 · Oct 25, 2023

DPG said:
The black tap will probably have seized due to lack of use. But if the pressure has dropped suddenly rather than just gradually over time, then it points to an issue somewhere in the system

Problem solved and pressure now sorted. The black tap was just stuck and extremely stiff, but just managed to turn it.

Thank you for speedy reply.

DPG · Oct 25, 2023

clueless456 said:
Problem solved and pressure now sorted. The black tap was just stuck and extremely stiff, but just managed to turn it.

Thank you for speedy reply.

Nice one. Keep an eye on the pressure over the next few hours/days to see if it starts dropping.

clueless456 · Oct 25, 2023

DPG said:
Nice one. Keep an eye on the pressure over the next few hours/days to see if it starts dropping.

Thank you. The pressure has dropped a little since it was reset - What things could cause this? Could it be caused by having heating up too high / too many radiators on / radiators o too high etc?

Should the pressure always remain at the same level, or is it normal to go up & down?

DPG · Oct 25, 2023

clueless456 said:
Thank you. The pressure has dropped a little since it was reset - What things could cause this? Could it be caused by having heating up too high / too many radiators on / radiators o too high etc?

Likely a pressure leak somewhere. Either in the heating system itself, or somewhere in the pipes/radiators.

Someone with better plumbing knowledge than me will hopefully be able to help a bit more.

Pressure vessels in combi boilers often leak, bit I'm guessing that red tank in your picture is an external pressure vessel?

littlespark · Oct 25, 2023

Bleed the radiators, then up the pressure again.

Air inside the rads compress more than water.

clueless456 · Oct 25, 2023

DPG said:
Likely a pressure leak somewhere. Either in the heating system itself, or somewhere in the pipes/radiators.

Someone with better plumbing knowledge than me will hopefully be able to help a bit more.

Pressure vessels in combi boilers often leak, bit I'm guessing that red tank in your picture is an external pressure vessel?

Thank you - I don't know if it's an external pressure vessel... I am a bit clueless with things like this.

clueless456 · Oct 25, 2023

littlespark said:
Bleed the radiators, then up the pressure again.

Air inside the rads compress more than water.

Thank you for the speedy replies. I'm sure I have a radiator key somewhere - It might be in a box somewhere in the garage.... I will try to find it.

littlespark · Oct 25, 2023

Bleed the rads when they’re cold.

Heating up the water increases pressure within the system anyway, but it expands into the air within the rads… and with the circulating pump running, it brings the overall pressure down.

If it’s like a combi boiler, optimum pressure should be between 1 and 2 bar when cold. Maybe a green mark on gauge showing good range.

clueless456 · Oct 25, 2023

littlespark said:
Bleed the rads when they’re cold.

Heating up the water increases pressure within the system anyway, but it expands into the air within the rads… and with the circulating pump running, it brings the overall pressure down.

If it’s like a combi boiler, optimum pressure should be between 1 and 2 bar when cold. Maybe a green mark on gauge showing good range.

Ok, thank you for the tip on bleeding them when cold. I have just ordered a radiator key, as not sure if I can find mine.

There is no green mark on the guage, but I reset it to the level marked on the bar which is set at just below 1.5... It has now dropped down to just below 1.

James · Oct 25, 2023

bear in mind that if you bleed air out of the radiators, the pressure will drop. you will have to add more water after bleeding to bring it up to the required pressure.

nicebutdim · Oct 25, 2023

Guage dropping to zero, then back from 1.5 Bar to 1.0 in a short space of time might be something more than air needing bled out of the system.

Is this the first time you've used the heating for some time or had it been working okay until recently?

Heating Lost Pressure

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