Fernox TF1 compact valve leak

[ReeceWood]

I've got a Fernox TF1 compact fitted in the airing cupboard, and discovered this evening after the boiler had no pressure that it is leaking.
I've seen previous threads about this where it leaks from the cap however mine appears to be leaking from the bottom inlet valve, not on the filter itself but the red tapped valve , where it connects to the filter.
I'm pretty certain it is a leak here and it's not water running to it etc.
I understand there is a washer between the valve and the filter ? Should I try and just nip up the joint first, or is it likely to need a new washer? Just dubious of over tightening considering its a plastic thread.
It is only a small leak and obviously has been going on for a while unnoticed .

 

[Burger]

Are you able to take and upload a photo? Might help us understand/see it better.

 

[ReeceWood]

Just a quick saved image but it’s leaking at the point I’ve marked .

 

[king of pipes]

They are a pain to seal at times it will need removing and the rubber seal replacing I put silicone grease on the washer to aid sealing they normally come with extra seals ? But are available on Ebay. Kop

 

[Rob Foster]

You can get a blue box of decent rubber rings in many diameters. from Aldi
for about £5 I have 3 boxes and use them as above in a variety of situations. AND NO I had no input into the TF1 in case anybody wants to know
Rob Foster aka centralheatking