Could a slight rad leak cause a massive drop in boiler pressure?

ferry

Noticed we had to fill up our boiler again as it dropped to 0 overnight
Looked around for leaks and spotted a very slight drip from a rad valve that I can only change at the weekend but want to know if such a small leak can cause a boiler to lose so much pressure overnight in just a few hours?
I can see any other leaks anywhere so also wondering if there is also an issue at the boiler?


Thanks

bris

No, check the outside overflow pipe from the PRV. It sounds more like your expansion vessel is either needing recharged or has blown.


If you look under the boiler you will see a 15mm pipe disappearing into the wall. That the one you will see from the outside. .


Re pressurise the boiler and see if the pressure rises over 3 bar, when the heating is on, that's when the prv kicks in.

cybervic

I had experience of a boiler dropping pressure cause by a leak but it wasn't so dramatic like yours, you would've spotted the leak before boiler drops pressure by that much.

ferry

bris wrote: »

No, check the outside overflow pipe from the PRV. It sounds more like your expansion vessel is either needing recharged or has blown.


If you look under the boiler you will see a 15mm pipe disappearing into the wall. That the one you will see from the outside. .


Re pressurise the boiler and see if the pressure rises over 3 bar, when the heating is on, that's when the prv kicks in.

Thank you.
I repressurised the boiler to 1.5 bar and turned on the CH but it rose to only about 2.5 bar.
Confirms the expansion vessel idea?


Appreciate the help

bris

ferry wrote: »

Thank you.
I repressurised the boiler to 1.5 bar and turned on the CH but it rose to only about 2.5 bar.
Confirms the expansion vessel idea?


Appreciate the help

No, if it didn't go above 2.5 bar then that's about normal if it was pressurised to 1.5 bar.


Did you check to see if the outside pipe is leaking? The prv won't kick in until it rises above 3 bar.
Are you still losing pressure quickly?

daveyjp

Overnight is a long time, minimum 8 hours? Certainly time for pressure to drop significantly, even with a small leak.

Our system pressure dropped quickly due to a towel rad which had a valve needing less than a mm turn to nip up.

On the other scale my dad over pressurised the boiler.

To reduce pressure I opened the towel rad valve a small amount so as not to have water everywhere, it was just dripping and within half an hour it had fallen back to normal.