I am trying to replace the cartridge in a recessed mixer shower in my house. I will no doubt have some issues identifying the correct cartridge, but am hoping that will be slightly easier once I remove it from the housing, which I can't seem to do. I have tried using an adjustable spanner, but it won't budge, and I am worried that I am starting to strip the 'nut', which is plastic (nylon?) not metal. I'm hoping someone might be able to answer a few basic questions for me.
1. Am I going about it the right way? This should unscrew, shouldn't it? If so, is it going to be a normal or reverse thread?
2. Do I need something like a box spanner, so that it locates right around the nut, or is there maybe a specialist tool needed for this?
3. The photo was taken with the retaining ring in place, but I removed this when I tried to unscrew. Is there anything else that might be holding it in place? I can't see a set screw anywhere.
Thanks in advance for any ideas.
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