Are they all the same size centre to centre?

Or are there different sizes? I ask as I have a leaking one and wondering if I need to isolate the water, take it off and nip to the plumbers’ merchants to ensure it is the right size or do I just buy one and fit it? (Basically – do I need to plan the job around when the merchants is open or not).

Cheers.

I always take a photo and show it to the plumbers merchant. Some valves have a 15mm compression fitting, others have a 3/4 male/female joint. I usually include a ruler in the photo too.

Mostly standardised. There should be a bit of adjustment built in to them anyway. UNless the designs are radically different you should be OK, especially if the one that is leaking is of reasonably recent vintage (say 10 years or younger).

It was fitted about 18 months ago with all new plumbing so I assume it’ll all be standard 15mm.

Do I risk it for a biscuit?

Are you sure you need a new valve if it’s only 18mths old and it doesn’t just need nipping up?

No, it is leaking from inside the valve part rather than the connectors and I can’t pull the cover off (at least I haven’t tried pulling too hard for fear of breaking it). And it was only a cheapo one that came with the radiator so I kinda assumed it was cheap and equally rubbish. I will take a look again at whether I can get the cover off though cheers.