Bath tap won't turn on fully

Hopefully this is a simple question. The hot bath tap in my bath won't turn fully on. The cold is OK (they are two seperate taps). The suite is only about 18 months old

The hot still works, but takes a while to fill up the bath!

Tried descaling but nothing doing...

Washer? Re-seating? Any ideas please?!

Thanks

Maybe it's low pressure from a tank, or from a combi, and the cold is from the mains???????

Thanks for the response, but all other taps are fine ...

OK I have seen posts like this loads of times before and can never be bothered to go into the detail. So as its xmas and its crap on the telly, I will.
1/ Turn off or drain down water
2/ Take off tap head weather crosshead dome or whatever.
3/ Undo main body going into tap
4/ Now you should have the tap insides out?
5/ remove circlip at the top of the stem
6/ Open the tap fully (while out of position of course)
7/ tap the top of the stem gently (till it all falls out in your other hand add a bit of grease)
8/ now you should have a piece with a worm type drive and a Hexagonal nut on the end?
9/ file the hexagonal nut (that I hope you have got)
10/ turn the spindle down as if you are shutting the tap off
11/ Now relocate into the hexagonal shape on that it came out of ( make sure it goes all the way in)
12/ now replace circlip and refit

Hopefully Problem should be sorted if not I will make a video and post it on here when I have time.

Hope this helps

all other taps are fine

Click to expand...

irrelevant, they're different taps.

Has this tap got worse??

Thanks Sime - I've done what you said and now the tap turns fully open and the hot floods out...for a brief few seconds...

I presume I've now got an airlock? Whats the best way to cure that?!

TIA

You will have to do it again but next time dont open the tap fully It won't be an airlock. If you open too much that spindle comes out and you have to do it again

Chris has mentioned what type of system you have got it would be an advantage to know.

Thanks Sime. I read up on airlocks on here, and tried the 'turn on the hot and cold and don't let any water out" trick using the basin in the bathroom (as this is a mixer), and hey presto, problem solved.

Thanks for your help!