My shower knob is seized

This is embarrassing.

It’s had increasingly limited movement for a while, but today it won’t even call on the boiler for hot water which is problematic. The range of movement is approx 45 degrees from cold to hot – neither of which are a thing.

I’ve blasted it with vikal, WD40 and stern words, but none of these have worked. I’d rather not a bathroom refit as I’ve still not got a kitchen.

Any ideas?

Turn water off, take it to bits and soak the cartridge in water/vinegar for a few hours. Alternatively, measure the pipe centres, order another bar shower with the same, and fit it to the existing outlets .

Limescale inside it has seized it up. You may get some more life out of it if you remove the tap (is it the tap end, or the temperature end?), and give it a good clean, however, that doesnt always work, and can ruin the o rings internally, and some of the limescale may not be removed without full dismantling of the valve, which will also likely cause leaks..
if you know the make and model, the Shower Doctor may have the spare cartridge/thermo valve for you, but, IME, its far easier and cheaper to just buy a new mixer tap. £80 ish for somthing simlar to yours, takes 10 minutes to change it.

+1 on scaled up tap cartridge being the issue.

+1 on it was cheaper to buy whole new shower bar. They are standard centres between pipes. Took maybe 30 mins to fit a new one – water off, undo two compression couplings, shower falls off, new shower, do up compression fittings, take a shower…

Rather than going through the Hussle of finding the specific knob, I’d just straight up tear that thing apart, it must not be reliable therefore not worth repairing, pick some other piping for the shower and voila, you’ve got a new working shower knob

Bristain shower, 6 years old and cartridge packed up new cartridge £172, new Bristain shower (complete) £268….

The right to uneconomically repair. I recently bought some shower screen spares (Matki rollers, guides), and you thought MTB bits were expensive????

The right to uneconomically repair.

I’ve got an electric shower which fails about every 4 years, same failure mode. First time I dismantled it and found a split diaphragm on the inlet valve. Can’t buy the 20p rubber bit, according to the manufacturer it’s not serviceable, (well I got it apart so…!) it’s a new shower ‘engine’ for 90 quid. Bastards.

The right to uneconomically repair.

It might seem stupid at first, but the amount of things that are built to break it’s incredibly high..

Pipe centres are standard at 150mm.

Just replace it with something cheap as it’s only two nut’s.

A mixer bar is a standard item.  Can be sourced cheaply and is easy to fit if you can turn off the hot and cold.

I had a Triton shower with an incorporated fixed head so didn’t want to swap it out. The Triton thermostatic valve cost ££s. The Amazon equivalent was cheap and worked great.

Pretty sure I saw a video about this – you need to get a man in with the right tool…..

Thanks all for advice – I think I’m doomed to a full shower replacement though as the overhead shower head is fed by witchcraft, rather that a standard screw type thing.

This is the new one, which looks vaguely similar so I’ll just measure up and get spending – that’s rubbish really, literally a complete shower! https://www.plumb2u.com/PBSCProduct.asp?ItmID=22648953

At the risk of stating the obvious, maybe get a different model than you can repair more easily?

I wonder whether that square riser does actually screw in despite initial appearances.

Isn’t there normally a grub screw round the back of those things which would allow you to just pull the knob off, as it were?

Edit: Had a quick look for it – looks like a cap you pry off with a screw fitting underneath. I think the one on the end helps you get at the temperature range adjustment. New cartridge is just over 100 quid, so a brand new bar shower is probably the best bet.

Better than seizing your knob in the shower.

Just attach a lever to it and force it.