Losing pressure...

[MICH43L]

Hi all.

Short version:
I have a combi boiler which is losing pressure.

Long version:
Boiler was losing pressure since around June/July. Put a bucket under the overflow and worked out that we were losing 1/2 pint per day.

Boiler was serviced and fitted a new pressure relief valve on 11th September, since when I've re-pressurised the system twice.

We're now losing about 1.25 pints per week down the boiler overflow (plus evaporation), and it's dropping from 1.5 to 0.8 in the same time period. It takes 27 seconds to fill it back up, which would seem like more than we're catching in the overflow bucket, unless the feed is very slow.

To give an idea of size, There are 14 radiators on the system.

(Full disclosure: I did replace and re-plumb a radiator back in November, but pressure tested everything and left the floor up for a few days to check it was OK. We've no obvious leaks coming through the ceilings anywhere.)

Haven't bled the system through in a couple of months. Going to do that later.

The heating has not been on. Just hot water.

I'm stumped as to the cause of the pressure loss, any ideas?

 

[ianmcd]

when you say over flow , do you mean pressure releif valve pipe work ? a combi boiler doesnt have an over flow, post some pics please

 

[MICH43L]

Thanks. Yes, the one in the centre leading outside.

 

[Elkato531]

The plastic pipe? that is the condense drain and should discharge water. The pressure relief is the one on the far left which goes out through the wall. You shouldn't have any water through this, if you do, your pressure will drop.

 

[CBW]

That’s your boiler condensate pipe, so if that’s the reason for the pressure loss, then it’s likely to be a cracked heat exchanger. Your condensate pipe should go to a drain, or soak away and should discharge water when it’s condensing. You may have a leak on your heating system if this isn’t the reason for pressure loss.

 

[terryplumb]

Does your pressure gauge get to around 3 bar when central heating is on ? As advised above ,check the pressure relief pipe outside to see if water is escaping there.

 

[MICH43L]

Thanks all, very helpful. I will check the other pipe. Heating has not been on yet.

 

[ianmcd]

If the heating hasnt been on and you are getting that much water from the Condensate discharge pipe (not overflow) most likely culprit is the heat exchanger, nothing you can sort your self I am afraid, and if as you say it is going into a bucket it is not installed properly

 

[MICH43L]

If the heating hasnt been on and you are getting that much water from the Condensate discharge pipe (not overflow) most likely culprit is the heat exchanger, nothing you can sort your self I am afraid, and if as you say it is going into a bucket it is not installed properly

The bucket was just a temporary measure to figure out where the water was going (and how much). Not sure what volumes of water to expect from the condensate pipe over the course of a week - any thoughts? Would a damaged heat exchanger not be picked up on a service? Are they expensive to replace?

Cheers

 

[ianmcd]

Nope wouldnt be picked up on a service, unless you state you have pressure loss, if the heating is not being used there should be next to nothing in your bucket, empty the bucket, turn the boiler completely off , no heating no HW and if you are still getting water in your bucket dear Lisa , it is indeed the heat exchanger, might still be under warranty though, if not Ideal fixed price repair is your best bet

 

[MICH43L]

Cheers. Every day is a schoolday