Hello group,

I have a shower cabin, Inisgnia GT8720. It has three control knobs, the bottom one being the temperature control, which is basically a thermostatic cartridge...

http://s760.photobucket.com/user/jon..._0307.jpg.html

It screws into the main unit, and replacement is simply a case of unscrewing the old cartridge from the unit and screwing the new one in. Insignia provide a video how-to he

https://www.youtube.com/watch?v=r0VV0XcQ1VE

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 turn the old cartridge, I cannot even budge it before the grips slip off, and 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 even tighter! I have also squirted in WD40 and some de-scaler in case it's clogged up but neither have had any effect.

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

Thanks
Jon