Call out to pigletjohn

[marsaline]

We have a major heating issue. Since about 6pm last night the system loses pressure completely whenever it is refilled. It drops down to zero really quickly. One of the upstairs radiators every 20 minutes or so sounds like someone is turning on a tap and then the radiator clanks and gurgles and sounds like all water is coming out of it. I’ve turned off the stopcock. No sign of large amounts of water anywhere.
can anyone help. I think maybe it’s a valve releasing the water out somewhere. Unfortunately we have an oil boiler so it’s always really hard to find a heating engineer

Does it lose pressure without the heating actually being on or only when the heating is running? If only when its running, then the next time you refill it and turn the heating on, watch what pressure the gauge rises to. If it rises to 3 bar and above, check the relief pipe that runs outside from the boiler.
What type of floor do you have downstairs - solid or suspended wood floor?

Solid floor downstairs. It looses pressure whether the heating goes on or the hot water goes on.

We haven’t actually tried filling it and then not putting either on but I think it will drop then too. It falls to zero pretty quickly

So we’ve now tried that and it still drops

It's probably the expansion tank. These have a rubber diaphram that perishes with time. There is normally an overflow for this which drips outside the house, so as pp says, look on the outside of the house for vent pipes with water dripping out. Sometimes the tanks are integrated into the boiler, sometimes they are elsewhere on the system, there may be more than one if the system is big.

How old is the boiler ?

Have you checked the boiler to see whether there is any leaks in it ?

All the water you put into the system has to go somewhere.

As PP said, this is likely to be an expansion tank issue. If you're lucky it will just be the valve and a quick repair. Otherwise, the expansion tank will need to be replaced. To test the value (looks like a car tyre value), just push in the pin - if water squirts out the the tank is knackered, if air comes out then its probably just a faulty valve.

We had this issue a few years ago - think it was about £200 for the tank (fitted).

Although the 1st plumber we used did the sharp intake of breath and "you need a new boiler" line. Sought a 2nd opinion and had it fixed.

thanks all. we found someone to come out today and they think its likely to be connected to an issue with the expansion tank so whilst they haven't fixed it yet they are going to look at that first. I'm just praying it isn't a leak since we have solid concrete floor and parquet flooring..

Some valves in the system are designed to evacuate the boiler/system if it gets too hot, they usually run to an outside point that is visible, but could be connected into another exit pipe somewhere, are you leaving hot water/heating on all the time and it is overheating?