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James I
James I, Plumber
Category: Plumbing
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The on/off knob on my shower mixer bar isn’t working. I’ve

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The on/off knob on my shower mixer bar isn’t working. I’ve removed the cap/housing to clean it but it wont turn/contact the valve. It feels like its running over a thread.
JA: I'll do all I can to help. How long have you been dealing with this?
Customer: A couple of hours.
JA: Do you plan on doing the work yourself?
Customer: If possible
JA: Anything else we should know to help you best?
Customer: I don’t think so, but happy to send pictures if needed
Customer: replied 1 month ago.
Hi just wondering if anyone had any advice on the question I asked.

Hi, thank you for choosing Just Answer, my name is ***** ***** I will help with your query today.

So you have double ended control with one knob controling flow the other temp on the mixer bar?

Customer: replied 1 month ago.
James, that’s correct. I *think* the housing on the flow valve has threaded so even when the fixing screw is tightened, it just rotates without biting.
Customer: replied 1 month ago.
I can send pictures if that’d help

Sounds possible but may just be the washer slipping.

If you remove the end cap from the flow knob you will see a screw remove that, and the knob will come off revealing the spindle, and its just a normal tap valve.

Turn off the water, use a spanner to remove the valve from the mixer and you can then manipulate it and see if it has threaded or not, but the cost of a valve I would just replace it anyway.

Customer: replied 1 month ago.
Thanks James. We can certainly do that. My only concern is that it’s the cap rather than the valve that appears damaged. Pretty sure I can’t get a spare for it, it’s old...
Customer: replied 1 month ago.
Or I maybe totally wrong!

I doubt the spindle is slipping but when you remove it you will see, getting a new knob to sit on the tap spindle probably easier to just replace the mixer tap as they will never match up as the finish will look different being all new and sparkly.

Customer: replied 1 month ago.
Ok. That’s what I feared, but glad to have my options checked with an expert. Can I ask if changing the mixer tap would be straightforward? IE no messing about with the boiler and plumbing behind the fixtures...

It depends on the type of fixing used, and the type of mixer is the honest answer, some eg ideal standard are just two bolts and they come away, others you have to replace the fixing which can be inside the cavity\behind the tile, in which case I might be inclined to actually use epoxy and glue the knob on the spindle, but as I say the chance of the knob being threaded is unlikely.

James I and other Plumbing Specialists are ready to help you
Customer: replied 1 month ago.
Ok James. Thanks for your help.