Trevi cold water cartridge is very stiff: should it be?

[gnnmartin]

I posted earlier that I had a problem with a Trevi Pre1996 shower mixer. The shower cut out, and I suspected it was because the cold water shut off.

I've taken it apart, and I find that the cold water cartridge is very stiff: it requires at least twice the torque of the hot water cartridge, and I believe they are meant to be interchangeable. I think what was happening is the cold water cartridge is so stiff that when the water flow knob was turned, the clutch slipped on the cold water cartridge, so only the hot water turned on. When the hot water reached temperature, the thermostatic valve cut out the hot water.

One solution is just to buy a pair of new cartridges. But is there any alternative? How stiff should these things be? Should I just try putting it back together with the clutch screw tightened, so the clutch is less likely to slip? Is there anything I can do to ease the cartridge?

I even wonder if one is meant to be stiffer than the other in order for the clutch mechanism to work properly: the paperwork does say you should replace both at the same time, which may be intended to ensure you get one stiffer than the other.

In case it is relevant, the shower has worked for several years of light usage before starting to give problems.
Nigel Martin

 

[seco services]

the flow cartridge useally only need changing when the shower head starts to drip.
but sometimes they do stiffen up. a cartridge is about £16
i'd be swinging more for a faulty clutch.
but a stiff cartridge can make the clutch look faulty
if you can free the cartridge up abit you may prove the clutch to be ok.
its swings and roundabouts.
with the cover off refit the handle
You can useally see if the cold clutch slips round whilst the hot doesn't until after it has made its full quarter turn. clutch kit about £20

 

[gnnmartin]

It feels a bit wasteful to order 2 new cartridges, but the maintenance sheet tells me I should replace both if replacing one. One cartridge is so much stiffer than the other that I think that is really the problem. Both clutch wheels seem much the same, and having worked the stiff cartridge on & off a few dozen times, and put a bit of silicon grease on the top in the hope it might help, the clutch still slips when I try to turn the cartridge on.

Thanks for your help. I'll report back when the bits arrive and I've seen if they work.