re-Pressurising a boiler

[wheypat]

Hi

About once a week I have to re-pressurise my boiler, which, to my way of thinking must indicate that water is leaking out of the central heating system. The boiler is on the ground floor and we have solid floors, so all the pipework goes up between the ground and first floor.

But . . . . . I can't see any evidence of wet patches, leaking radiators, damp walls etc.

Where is the water going?

[oldcharlie]

I am just a consumer with a Worcester Bosch combi from BG regularly serviced. For many years I lived with this tall tale of a leak umder the concrete floor and constantly falling pressure. I was told that a lot of folk just leave the grey tool to re-pressurise engaged all the time.

Then one day it didn't respond to the normal re-pressurising routine and dropped as soon as the gas service man left the building. BG came back changed three parts on the boiler and I have never had to re-pressurise between yearly routine service visits.

OC

[Watis]

I too have a Worcester Bosch condensing combi boiler which also experiences very slow pressure loss and again I have no evidence of an actual leak.

What I do have to do frequently is bleed one of the radiators, maybe once a fortnight, and this task appears to be responsible for the gradual pressure drop. What I don't understand is how this gas that I bleed off, being less dense than the liquid it must have been generated from, doesn't result in an increase in system pressure.

Oh, and why am I having to bleed this radiator so regularly anyway?

Any ideas?

TIA,

Watis

[passinthru]

I had this trouble for many months and kept a close eye on where the small leak could be. This was without seeing any loss anywhere. My friendly boiler man soon spotted it though. The heat exchanger had a pin hole leak and the water was being evaporated quickly so no actual visible leaking to the outside of the boiler.

Passinthru

[IsleofWightPete]

Hi

About once a week I have to re-pressurise my boiler, which, to my way of thinking must indicate that water is leaking out of the central heating system. The boiler is on the ground floor and we have solid floors, so all the pipework goes up between the ground and first floor.

But . . . . . I can't see any evidence of wet patches, leaking radiators, damp walls etc.

Where is the water going?

Usually, when you cant see where it is going, it is leaking out of the pressure relief valve. You can check this by putting a small poly bag over the end of the pressure relief pipe outside, using an elastic band to secure it on.

You will quickly be able to see if water is collecting in the bag.

[brightncheerful]

We have a Vailant combi. At every annual service, and sometimes during the intervening period, I ask the heating engineer to adjust the pressure so that the needle on the gauge is roughly at the same position as he told me it should be. Every so often I have a look and check nothing amiss. I'm told that there is a slight leak in the system could be anywhere, pipework, radiator valves, etc. This has been happening for years.

A couple of weeks ago after I'd noticed the needle had dropped quite a lot from its normal position, the engineer noticed that a part in the boiler looked corroded which he thinks is the cause. He said he'd order a new part, it should've arrived by now, the op has reminded me to contact him to get it fitted.

[brightncheerful]

Usually, when you cant see where it is going, it is leaking out of the pressure relief valve. You can check this by putting a small poly bag over the end of the pressure relief pipe outside, using an elastic band to secure it on. You will quickly be able to see if water is collecting in the bag.

Our service engineer released? some water with a view to checking. There is a pipe outside but no water came out of it within a few minutes and nothing since. The pipe was put in when the house was built but we've had a new boiler fitted since then. We think the pipe for the pressure relief has been connected to an internal pipe somewhere in the house that is connected direct to the drains. Unless the company that installed the new boiler can remember, the company stopped doing domestic heating boilers many years ago no other way to find out short of removing all the floorboards, etc.

[wheypat]

Thanks for the replies. The boiler is due it's annual service next month, I will mention it to the engineer.

[quelquod]

We think the pipe for the pressure relief has been connected to an internal pipe somewhere in the house that is connected direct to the drains.

The pipe outlet outside is likely for draining down the system. Sounds like it wasn't a smart move to connect the relief elsewhere, especially somewhere hidden, as you now can't tell if it's seeping. It's likely been connected with the condensate drain.

[seekingbalance]

I used to have the same problem in my last house. When trying to find the problem the engineer, a friend, said that the reason you often can't see any leakage is that the leak can be very small and the water released evaporates so you don't see any residue anywhere.

As others have said, the problem is there are so many places this could be happening - every joint, every valve on every rad, the boiler, the tank, the pressure vessel itself.

Mine proved to be a leak around the pressure release valve, as IsleOfWhitePete suggested.

SB

[seekingbalance]

Oh, and why am I having to bleed this radiator so regularly anyway?

Watis

A number of causes, probably from one of these:

Sludge in the system caused by not having enough rust inhibitor, as the rust forms gas (hydrogen I think) is given off
A leak somewhere, losing water, gaining air
Air trapped in the system being gradually getting to the highest points
Leaky pump pushing air into the system