Heating system losing pressure...

M

MummyBT

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hi, we have a problem with one rad not heating (last couple of months) and boiler losing pressure (only discovered this over the weekend). We repressurised to 1.5 bar yesterday and it went down to 0.5 overnight. We refilled again and will check if this has changed in the morning. The questions I have are:

1) what would cause a rad (probably last in the circuit) to only heat when all others are shut off? It’s the only one with a fully open lockshield. It has been bled, as have the others.

2) other than a leak, what would cause the boiler (installed 5 months ago) to lose pressure from 1.5bar to 0.5 overnight?

3) could the fact that we have recently (1 week ago) changed from only heating on demand to thermostat controlled heating (set to 19 degrees) have something to do with the pressure issue?

Thank you!
 
Q1) no idea
Q2) nothing, imho
Q3) don't see how

Sounds like a job for a heating engineer/plumber
 
If you have bled out any air then you have a leak which could be in a number of places, the expansion tank on the boiler is a suspect especially if the tank is old, it is a job for a gas qualified plumber.
 
The problem with the last rad not heating may be down to an air lock, a blockage caused by sediment in the system, a poorly balanced system or insufficient pump pressure.

In relation to dropping pressure, a leak is the most likely cause. Only other thing I can think to check is whether the top up valve was left open?
 
The final rad only heating when the others are off is probably an issue with balancing. If so, you get to play with the in and out valves on your rads until they are all heating.

A blown expansion vessel would be my first suspect for the pressure dropping, except you say the boiler is only 5 months old. Check underneath your overflow pipe and see if water has been coming out.

I suspect you're going to need a heating plumber out, so you might as well leave him to sort out balancing the radiators along with everything else.
 
Thanks, everyone. So we’ve had a development this morning. Pressure was unchanged from last night at 1.5bar until I had a shower and it dropped to 1bar.

We inherited what I think is an odd set up when we bought the house over two years ago. We have a pump in the hot press which “drives” water to the en suite shower. The pump I believe was installed separately to increase flow through this paricular shower. All other showers in the house (2) are tritons.

Is it possible that the shower is pinching pressure from heating system, resulting in rad not working because hot water just isn’t getting to it? I thought they were completely separate isolated systems but I don’t know much about it so could be talking complete rubbish!
 
Separate systems alright, you could do with somebody looking at it for
you, heating systems can be unique enough, mine certainly is with a stove heating water and rads and a gas boiler as a back up
 
Came home to find a small pool of yellowish water beside the washing machine. This is getting a bit ridiculous o_O

At least I now know there is a leak!
 
There is a small possibility of the shower pump pulling water from the heating system. but only of the filling loop is open, and even then very much depending on the layout of the pipework to both systems.

Is there a rad near that washing machine? Or do the rad pipes run near it?
 
The boiler is very near the washing machine but no rads.

Filling loop is definitely closed...
 
We have two. Husband dearest just checked behind the washing machine and came to the same conclusion.

We have a 5 months old. I don’t sleep much. That’s my excuse :confused:
 
JohnJay said:
You don't have a cat by any chance? :D
Click to expand...

Great minds ...... the colour yellow suggested to me immediately that it was a dog or cat.

Getting back to the original problem, I've experienced something similar in times past and Leo has hit the nail on the head, in terms of what was causing the problem in my house.... it was down to balancing the rads.

With regards to the pump, we have a "standard" semi-d and have a main bathroom, along with a shower in the en suite and also, a third toilet downstairs. We have a 3.5 bar pump and we were told that was appropriate for the size of the house with 2x showers, 3x toilets, and 8-9 rads. How does that compare to your set up, MummyBT ?
 
Yup, pretty standard semi-d here too, 3 showers (2 tritons, one as described), 3 toilets, 7 rads plus 3 heated towel rads in the bathrooms. The rads upstairs work like a dream, downstairs less so with the living room one not at all. Does the balancing issue just happen randomly or what causes it? Not that it matters, but I’m just curious because all rads were working perfectly back in June when we had the boiler replaced...

Thick question: how do I know that we have a circulation pump and that it’s working? Or should we have it at all?
 
Last edited:
MummyBT said:
Thick question: how do I know that we have a circulation pump and that it’s working? Or should we have it at all?
Click to expand...

The pump will look something like [broken link removed]. It'll be located close to the boiler, and when the heating system is running, you'll be able to feel a low vibration as the motor runs.
 
Leo said:
The pump will look something like [broken link removed]. It'll be located close to the boiler, and when the heating system is running, you'll be able to feel a low vibration as the motor runs.
Click to expand...
if you have a new boiler, there is a good chance that the pump is built in to the boiler so you wont see it.

I might be wrong, but I dont think your showers will be causing the pressure issue with your heating. They are 2 separate systems. The manky black water in your rads doesnt come out of your shower head! :)
 
Don’t see a pump in the hot press and the boiler is new so makes sense.

Our bedroom rad was making gurgling noises when the heating came on at night = air in the rads? I’ll bleed them again today either way and see, then will get husband dearest to tighten all joints - I’m a weakling, maybe it’s me causing slow leaks by not closing them tight enough...

Meanwhile pressure was down to 0.5 bar again earlier today. I just really really really can’t deal with a leak right now
 
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