Hallelujah!!!
Thanks to all who have taken the time out to reply. I’ve been on two talk groups and the last comment from one of them sorted it for me. Unbelievable! Basically by opening the pressure release valve (PRV) and letting it snap shut hard a couple of times, I can only guess it has “seated” properly. Before this I was releasing pressure and letting the valve return lightly, the “snap” seems to have sorted it. So simple, but this is where “tricks of the trade” come in.
Saved myself a few bob, and more importantly if whoever I brought in didn’t know this trick, then I could’ve been paying for a lot of hours messing about.
I have put all the replies below as some of these suggestions may help others.
My thanks again to all who have taken the time out to help.
RELPY ONE
It can only be your new part is faulty!!!!
RELPY TWO
if it still drips at 1.5 bar then its possible the pressure gauge is at fault.(giving a reading lower than the true pressure)
MY REPLY TO ABOVE
I'm going to try replacing the valve again first as another topic group have suggested this
REPLY THREE
Its more likely you have dirt in your system which is causing the new valve to fail to seat properly!
Have you watched the gauge as the boiler heats up the radiators?
Does the valve leak at 1.5 bar or do you watch the pressure rise to 3 bar and then leak?
I presume you fired up the heating before the new one leaked, yes?
MY REPLY TO ABOVE
The valve leaks at 1.5 bar with the water cold
but no I did not fire up the heating, this is all with electric mains to the boiler switched off, and the system cold, so there is no additional "heat" pressure.
Any other ideas, I'm still fancying the new faulty part, but that's because I'm hoping it's that simple.
REPLY FOUR
make sure the prv is shut by twisting it and let snap shut you can unscrew some and clean the seating.