Boiler dropping pressure

[altafica]

My boiler keeps dropping pressure. Every morning for the past few weeks it does not come on automatically and I have to repressurise it, also the dial does not tell my what the reading is. Twice this week it has dropped again during the day when I was at work. One morning last week it did come on in the morning, how strange?
Its a heat line, came with the house 5 yrs ago, so is about 8yrs old. I can not afford to change it, so really need to get it repaired. Any body have an idea what it could be, and what sort of cost it would be?
Thanks

 

[Whitespirit66]

Have you seen water dripping from, the pressure release (copper) pipe that goes from boiler, through the wall to outside? Tie a plastic bag over the end of pipe to see if water collects in it.

 

[MANDATE]

I don't think it's that strange. There is a leak
The opening and closing of the PRV when the pressure gets up to 3 bar would result in a large drop in pressure in seconds so you can discount that one.
If at some time the PRV has been opened manually during a service it could well be it has not closed properly. Sediment on the valve seat would leave you with a small leak and the pressure would drop, although over a longer period 'overnight' or 'during the day'
The other alternative is that the PRV is OK and the leak is in the heating system perhaps at the radiator valves.
It is common practice to isolate the system from the boiler overnight to see if the pressure drops or not indicating which side is at fault.
It might be worthwhile replacing the PRV for a new one if you can't find any leaks anywhere