Worcester filling loop leak, can I turn it off?

[crtgodd]

Went to repressurise the boiler. After tightening the square bit, and removing the key (key in unlocked position), there were some drips coming out. It seemed continuous rather than the left over splash that normally comes out. I only used my hand to tighten it but I did it quite tight.

I put the key back in and left it unlocked in hope to stop any water coming out.

Questions:
I'm guessing the plastic part that the key goes in can be replaced, Worcester Greenstar 30 Si model? Any idea on price?

There's two brass bits behind it with screws on the bottom, can I use these to shut off the water to the filling loop in case it has a continuous leak? There's no other taps on the pipes going in.

Obviously we should get an engineer but last time we had to wait a week after calling all the ones we could find and I'd rather not have something continually leaking.

Is it ok to leave the key in the unlocked position like that?

 

[Iddy]

If it's leaking from the mains side i.e. the isolation valve with the square white knob is 'passing', it'll slowly pass water across to the heating side if the white key is left in. The white key forms a channel between the 2 sides (water passes across between the o rings on the key). Being in the locked or unlocked position makes to difference, other than being able to pull the key out. Many do leave the key in, though it ought to be taken out after filling to comply with water regs which state that there shouldn't be a permanent connection between portable cold water and the contaminated water in the heating system.

 

[Iddy]

You can replace it by turning off the 2 isolation valves on the brass valves behind (mains inlet and central heating return), removing the grub screws with an Allen key (should be 4 altogether). Silicone grease on the o rings on fitting the new one...

 

[crtgodd]

So is there a one way valve in the black plastic filling loop component to stop the heating water coming back out when the key is out?

I did see on YouTube some swapped it with a keyless loop, that would be better I think. Though this is quite old so the current piece will probably be brittle and hard to remove. I might give it a go but I always have trouble with plumbing and things still end up leaking afterwards.