Oil Boiler Pressure dropping

AstraMonti · 17-09-2019 11:02am #1

Hi guys,

Would there be another reason -apart from having a leak somewhere in the system - that the oil boiler pressure drops and needs often topping up?
When the system is full, pressure is about 0.7 and when it's working it's about 1.5. If you leave it for a couple of days pressure drops to around 0.3. All rads are heating up fine.

Many thanks.

Wearb · 17-09-2019 12:48pm

On the face of it that seems normal. The difference between 0.7 and 0.3 might be accounted for by the difference in being off for 1 day and being off for a couple of days. Put it to 1 bar when its at 0.7 and see if it still drops to 0.3 after a few days. But I suppose the fact that it often needs topping up does point to a leak or paragraph below.

Anyway to answer your question; the pressure relief valve could be letting by or radiator valve spindles etc.

AstraMonti · 17-09-2019 1:47pm

Thank you. Apart from seeing a wet spot on the wall/floor, is there a DIY way of finding leaks?

AstraMonti · 17-09-2019 6:01pm

So I filled the system yesterday. I just got back home and I just saw this thing in the picture dump a large amount of water to the drain behind the wall. Why would it do this?

Pressure is now 0.
Anyone to shed some light please?

K.Flyer · 17-09-2019 6:09pm

That's a condensate trap which is meant to dispose of condensated water from the boiler and has no bearing on water pressure.
Water would normally only pass through it when the boiler is running or very shortly after it has stopped.
Top up the pressure again but do not run the boiler for 24 hrs and see if you can detect a trickle of water through the pipe from the trap during that time.

AstraMonti · 17-09-2019 6:12pm

Thanks very much. The boiler had just started working when it start dumping the water. I can't quantify the amount, but it was a full blown stream of water going for a solid 30seconds.

Tom44 · 18-09-2019 9:35pm

Pressure doubling from from cold to hot .7 bar to 1.5 bar is not normal and indicates a flat pressure vessel in my book.
Pressure should only go up by 25%

Dtp1979 · 19-09-2019 5:08pm

If the pressure is repeatedly settling at .3 and not going to 0 then chances are the coil is leaking on the hot water cylinder

mrblack · 20-09-2019 7:35am

AstraMonti wrote:

Would there be another reason -apart from having a leak somewhere in the system - that the oil boiler pressure drops and needs often topping up? When the system is full, pressure is about 0.7 and when it's working it's about 1.5. If you leave it for a couple of days pressure drops to around 0.3. All rads are heating up fine.

Dtp1979 wrote:

If the pressure is repeatedly settling at .3 and not going to 0 then chances are the coil is leaking on the hot water cylinder

Test the expansion vessel for leaks. I had a similar pressure dropping problem for ages and found water coming out the valve when I tested it. Changed it myself and now pressure is stable again.

AstraMonti · 20-09-2019 2:49pm

mrblack wrote: »

Test the expansion vessel for leaks. I had a similar pressure dropping problem for ages and found water coming out the valve when I tested it. Changed it myself and now pressure is stable again.

Is it a DIY job?

AstraMonti · 20-09-2019 2:52pm

Dtp1979 wrote: »

If the pressure is repeatedly settling at .3 and not going to 0 then chances are the coil is leaking on the hot water cylinder

Thanks, the cylinder is 3months old, had the problem before installing it too.

Oil Boiler Pressure dropping

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