Replacing thermostatic cartridge in shower cabin - can't unscrew old one

[Jon Parker]

Hello group,

I have a shower cabin, Inisgnia GT8720. It has three control knobs, the bot tom one being the temperature control, which is basically a thermostatic ca rtridge...

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It screws into the main unit, and replacement is simply a case of unscrewin g the old cartridge from the unit and screwing the new one in. Insignia pro vide a video how-to here:

This shows the process but it is not necessary to remove the entire 3-knob unit from the shower, you can do it in-situ.

Here's the trouble - using my grips I am unable to get enough purchase to t urn the old cartridge, I cannot even budge it before the grips slip off, an d I am using all of my strength.

I'm now in need of a way to try and unscrew this thing. I thought initially about a gentle heating, but I don't want it to expand as it will make it e ven tighter! I have also squirted in WD40 and some de-scaler in case it's c logged up but neither have had any effect.

I'm now looking for some suggestions as to how I can unscrew this thing!

Thanks Jon

[Roger Mills]

Have you tried locking a Mole wrench onto the knurled bit, and then tapping it round with a rubber mallet.

I sometimes need to do a similar thing with the cartridges in basin taps

- except that I can use a ring spanner on those. If - as is often the case - they won't budge with just hand pressure on the spanner, tapping it with a rubber mallet usually does the business.

[Capitol]

Seems like a standard right hand thread device. I'd try to rotate it anticlockwise with the grips whilst gently tapping the knurled end with a hammer. The impact vibration may free up the threads sufficiently for it to turn. Too much turning force alone might be a problem as you do not know how well the back unit is located. Heating it with a hair dryer before spraying with WD40 may help with penetration. I guess careful persistence is called for.

[newshound]

+1 for Moles. I assume you are aware that you need to lock them on *as tightly as you possibly can* by adjusting the screw. For a hex device, start by using the flat jaws at the tip, and if that doesn't work (I almost said *when* that doesn't work) use the rounded part of the jaws. On Knurling, use the rounded part.

I've even had good results with a Mole on chrome plating, after wrapping the part with numerous turns of duct tape to protect the finish. The Mole is probably my favourite non-power tool when it comes to fixing things. Not sure if I would place it just before or just after a bench vice.

I agree about rubber mallets too.

[Roger Mills]

Horses for courses! Much more portable - you can't always bring the workpiece to the vice if, for example, it's attached to your car.

Apart from the usual DIY, I find my Mole wrenches (I've got several - including a few unbranded clones) excellent for cracking crabs' claws to get the meat out. You can assert a very high force over just a short distance, without any danger of crushing the thing completely.

[Fredxxx]

I might suggest pipe wrench, pump pliers or Stilsons, that increase their grip as you turn.

[Jon Parker]

All sorted. Used a tool which I don't know the name of but it's for getting to the back-nuts on the underside of bath taps which are impossible to acc ess otherwise. This has a spring-loaded grip on it and a T-bar at the end, this was able to grip the knurled bit hard enough to crack it off, after th at it came out by hand.

New one in with a bit of PTFE tape and so far so good.

Cheers all. Jon

[Huge]

A tap spanner.

[newshound]

Mine come out at Xmas as nutcrackers!

[newshound]

I put in immersion heaters with something like ten layers of PTFE tape for the same reason.

[Roger Mills]

Yes, excellent for that too. You can crack the shells without smashing the innards to smithereens.