Help! Boiler losing water pressure!

Devon

Our gas boiler seems to be losing water pressure even though we keep topping it up. I bled out the radiators and the pressure dropped down to 0 so I opened the water valve and filled it to 1½ but it's back down to just over ¼ bar of pressure.

If we call out someone, is there an easy way to detect if there's a leak somewhere in our central heating system or are we talking about pulling up random floorboards?

Thanks folks.

spacenut66

the first thing to check is a valve under the boiler it should have a red cap on it. this is a pressure relief valve, if you system goes over 3bar it automatically opens, these valves often let by. the prv will have a discharge pipe see where it terminates. if its dripping water, thats the problem.

Devon

It's never gone anywhere near 3 and I know the pipe you're talking about - it terminates outside our house, and it's dry.

spacenut66

thats a pity! the leak must be on the ground floor but there is no way of pinpointing it unfortunetly. if the leak is slow it may be worth putting leak sealer in the system it comes in a syringe type applicater and is injected through an air vent on a radiator, although it only works on the smaller leaks so i don't know if it helps! It could also be the expansion vessel it is either located in the boiler or externally (big and red), this may need pressurising! best of luck!

Devon

Thanks for that spacenut66. I'll look into that leak sealer. Appreciate your time.

crosstownk

A few items could be leaking. I'll assume you've checked the flow and returns at each radiator as well as each bleed valve . Next check the automatic air vent which usually sits beside your hot water cylinder - about the size of a grenade with a screw valve on the top. Also check your expansion vessel - usually a round red coloured cylinder sometimes mounted either in the attic or above the boiler, but if the house is old it could be anywhere. Also check any motorised valves that may be fitted.

Have look at the ground floor ceilings to see if there are any signs of a water leak from the upstairs pipework.

When you check the pressure, be sure that the system is at a similar temperature to when you checked it last as pressure will vary with system temperature. I find it best to check when the system is cold. Hopefully something will show and save you having to rip up floorboards.

JamesM

Devon wrote:

Thanks for that spacenut66. I'll look into that leak sealer. Appreciate your time.

You would want to be very careful taking the vent out of a radiator, do it at the wrong time and you can have scalding water all over the place.
If the expansion vessel is over 10 years old, the diaphragm could have split. The pressure would build up because of lack of expansion, and force water out at valves or anywhere it can escape.
Jim.

Stoner

I had the same problem, and a leak sealer fixed it

brn1

My problem is that the pressure on my boiler is above 3 bar and it discharges outside. I recently had an attic conversion witha radiator added and since then I have had this problem. The prv was replaced at the time but it still hasn't solved the problem. Any advice? Thanks.