Repressurising Central Heating...

[dibbers006]

The initial message was deleted from this topic on 26 April 2026 at 20:12

[Seany88]

On my combi all I need to do is open up a filler valve which adds water into the system thereby increasing pressure. Took me awhile to find though, but guess just have a scout around your boiler and look for a one-way valve somewhere?

[andy-xr]

1.5 seems quite high, mine's set to .5 and goes up to 1 bar with heating and hot water on

I'd guess you turn those 2 black taps? Have you got a key to bleed a rad incase you get a bit too eager?

[HRG]

Seany88 said:

On my combi all I need to do is open up a filler valve which adds water into the system thereby increasing pressure. Took me awhile to find though, but guess just have a scout around your boiler and look for a one-way valve somewhere?

He shouldn't have to look too far judging by those pics

[F i F]

I'd be cracking those valves at each end of the flexible, ever so carefully and see what happens, if the pressure rises then shut them again once it is at 1.5 bar.

If the pressure drops too low the boiler will shut down I'd guess. 0.5 bar is typically just above the point where that might happen.

[andy-xr]

dibbers006 said:

Which Black Knob are you putting your money on then?!!

These look the favourites to me

[robinhood21]

The pressure has dropped because you have bled the rads. As mentioned, open any one of the two taps on the end of the flexible tube. Then slowly open the other tap until the pressure increases to 1.5bar. This should be done when the heating is cold, as hot water will increase the pressure a tad over 1.5.

[Seany88]

HRG said:

Seany88 said:

On my combi all I need to do is open up a filler valve which adds water into the system thereby increasing pressure. Took me awhile to find though, but guess just have a scout around your boiler and look for a one-way valve somewhere?

He shouldn't have to look too far judging by those pics

Damn slow comp didn't load any pics...

[dealmaker]

Agreed, it's the black valves controlling cold water into the system.

I have a smiliar set up and the "MegaFlow" (excellent invention!) seems to like to run at about 1.3 to 1.5 Bar.

The problem will be if you top up the pressure and then it falls again! ....if so the you have a leak!....ask me how I know!

I have to top up the pressure in mine about once a week - what a pain - I must have a bad fitting under one of floors on the ground floor of the house. There's about a 10" gap under the floor between the flooring and the concrete pad.

Becausie I don't want to go round pulling up the WHOLE houses hardwood flooring - does anyone know of a quick way of establishing the whereabouts of a hidden leak??? I don't suppose theres some sort of natty camera you can send down you heating pipes to explore for leaks is there??

Sorry for Hi-Jack!

Edited by dealmaker on Monday 15th December 15:55

[andy-xr]

dealmaker said:

Agreed, it's the black valves controlling cold water into the system.

I have a smiliar set up and the "MegaFlow" (excellent invention!) seems to like to run at about 1.3 to 1.5 Bar.

The problem will be if you top up the pressure and then it falls again! ....if so the you have a leak!....ask me how I know!

I have to top up the pressure in mine about once a week - what a pain - I must have a bad fitting under one of floors on the ground floor of the house. There's about a 10" gap under the floor between the flooring and the concrete pad.

Becausie I don't want to go round pulling up the WHOLE houses hardwood flooring - does anyone know of a quick way of establishing the whereabouts of a hidden leak??? I don't suppose theres some sort of natty camera you can send down you heating pipes to explore for leaks is there??

Sorry for Hi-Jack!

Edited by dealmaker on Monday 15th December 15:55

When water drip on head, look up and leak shall be found


/chinesemaster

[robinhood21]

dibbers006 said:

robinhood21 said:

The pressure has dropped because you have bled the rads. As mentioned, open any one of the two taps on the end of the flexible tube. Then slowly open the other tap until the pressure increases to 1.5bar. This should be done when the heating is cold, as hot water will increase the pressure a tad over 1.5

Ok excellent. Thanks. If I am not here tomorrow could someone send a search party

I suggest donning a safety harness. Then with the use of a bungee, tether yourself to the gatepost. With all doors in the open position, claw your way up the path, through the front-door, and up to the boiler keeping a firm grip on the largest of the pipes. Then, carefully adjust the water pressure. If there are any strange noises, release hold of pipe, thus exiting in a speedy fashion.

[F i F]

The m-i-l had that problem, ie pressure drop. Turned out it was a dodgy valve in the boiler and the leak was to an overflow. It was only when the dodgy valve more or less totally failed that the leak was found.

Though to be fair it didn't help with the dopy mare not having had the boiler serviced properly for a few years!!!!

[martin thomas]

Remember that the pressure will increase as the temperature rises!! I would set it to 1.2 bar that way when hot it will be about 1.5 bar.. Also the more fresh water you put in your system means that the additive will be getting weaker!! If you are consistently topping up the pressure..ie if you have a leak you may suffer with corrosion or rock build ups..



Martin

[Ferg]

I'd set it at 1Bar cold, it's plenty.

Any leak in a heating system is bad news. Fresh water means oxygen which means corrosion. Steel radiators, iron pump, possible iron heat exchanger..... Rust!!

There are several internal leak sealers available which you simply pour into the system (through a radiator vent on a sealed system). The leak described above is small enough to be sorted with leak sealer in my experience.