Boiler dropping 3/4 bar pressure every 24hours

[AidanGee93]

Got a 23/4 year old combi boiler (vokera) runs good and no issues with heating but I am expecting to change sooner rather than later.

 

I've been topping my pressure up every other night as I notice it drops 0.5. - 0.75 bar of pressure every 24 hours... wondered why?

 

Recently fitted new radiators and one of them at the tail Valve has the smallest drip (I wrapped 20 times in ptfe)...it's so small I only noticed a few drips on the laminate and I've since put a cup under it, every couple of days I'll throw the water away but it's no more than a few drops of water.

 

Another existing rad had similar, but drops were from the thermostat rad Valve so I just closed that off and no leaks. (Closed just as I'm not using that radiator)

 

Could this pressure drop from boiler be caused by the leaky rad tail Valve?...just find it mad for the pressure to be dropping from a few drops of water.

There's no other leaks anywhere, no signs of water stains on ceilings etc from pipes...mabey a leak under the house in crawl space? 

 

Any ideas, appreciated 👍 

[Nickfromwales]

Probably blowing out of the PRV (pressure relief valve). 
 

Check to see if the blow off pipe, the 15mm copper pipe poked out through the wall, is letting water out. 
 

Zip tie a sandwich bag over it, making sure rain can’t collect in it and give you a false reading, and report back.

 

A few smallness leaks will defo have an impact, but maybe not as much as you’re seeing. Possible cause is the expansion vessel has snuffed it, or needs re-pressurising. 

[Andeh]

We had a pressure drop similar to that, and it was a failed expansion vessel. Some damage had allowed it to rust through.