Help putting back shower valve

[Dedekind]

Hello

We had a new bathroom fitted 6 months ago, today I was cleaning the shower valves and one of them simply snapped off. It is one of those thermostatic mixer valves. The cartridge is Ok, in fact I can put the valve back and move it and the shower works fine, but the valve is a bit loose and comes out again unless you are extra careful. Some pics attached

Seems like there should be a washer somehow that's missing? It wasn't loose before, I.e., we couldn't simply remove it by applying moderate force. The second valve is Ok in this sense, also not easily removable.

I suppose this should be easy to put back but have no idea how. My bathroom DIY skills are pretty non existent.

Pictures here
https://imgur.com/a/QlMaEZO

 

[CBW]

There’s either a grub screw underneath that wants tightening back up, or a screw behind a cover cap on the valve head.

 

[oldbuffer]

1. It doesn't look as if there is a grub screw to hold the knob on. No hole in the visible side of the knob, nor in the visible part of the female splines.
2. Also doesn't look as if the top of the knob comes off to reveal a screw. The moulding marks on the inside underneath the top suggest its one piece.
3. So logic suggests its a pull off knob.
4. It's possible there was an O ring on the spindle, below the male splines, to hold the knob on. Maybe this was omitted / has got lost.
5. Try:
5a. Pulling the other knob off to see if that is held on in the same way, and whether it has an O ring or similar holding device. If so, replace with similar on the loose knob.
5b. Fitting an O ring which is a tight fit over the narrowed blank below the male splines. Measure the diameter if you can, otherwise get the circumference by wrapping thin string round once and marking a line over the point where the the ends cross. Measure the circumference, multiply by 7 and divide by 22 to get a fair idea of the diameter. Then see if the knob hold tight.
6. Alternatively, get the make and model of the shower (possibly from the bathroom fitters?) and work out how its attached by means of the parts diagram.

 

[Dedekind]

Sorry forgot to reply! There is a grub screw and I managed to put it back in 20 seconds. Thanks!!!