TMV constantly leaking in gasket inlets

[john2k]

I purchased the following tmv thinking it’s a good brand as there were cheaper ones but thought would go for slightly more expensive: https://www.bes.co.uk/inta-intamix-thermostatic-mixing-valve-15mm-with-isolating-valves-26803/

The two inkers have a compression fitting to the isolation but from the isolation to the main tmv body the there is a rubber gasket. I’ve made sure this rubber and the face of the body and the fitting is aligned before tightening it but it forever constantly leaks. I don’t want to keep tightening it. I’m thinking to return it. But wondering are there any good ones that dot have this rubber fitting and just rely on compression alone?

 

[Exedon]

Assuming face's are flat just change washers either rubber fiber or we now use kevlar washers on flat faced joints.
Don't over tighten.

 

[john2k]

Assuming face's are flat just change washers either rubber fiber or we now use kevlar washers on flat faced joints.
Don't over tighten.

I’ve attached a few pics. The two faces are flat and they provide this really thick black rubber that’s the exact size of the flat surface. But problem is the the main nut that comes and tightens to the body doesn’t not have anything that keeps it perfect centred so I think it just doesn’t sit perfectly. When I remove it I find the rubber has ended up outside the flat surface into the threads.

 

[john2k]

Also, please see the the pics below. I think there is something fundamentally wrong here. That bit that goes to thread into the body is supposed to surely sit perfectly centred to that body metal ring. I hope that makes sense. But if you look carefully you will see that it doesn’t. Unless the nut is never supposed to go in enough to need to self centre with the inner part

 

[oldbuffer]

Just a thought. In your first picture the rubber washer appears to have a lip to it. Is it the right way round or is the narrow diameter meant to go inside the fitting with the broad back of the washer against the flange?

 

[avonmouth]

That looks like a badly machined fitting and is why it will not tighten up flush.

 

[john2k]

So I’ve managed to make it work without leaking so far. Keeping an eye on it for the next 24hrs see how it goes. But definitely think it’s very poorly designed. I had to completely removing it and have someone hold the two fittings 100% straight while hand tightening the nut. Making sure the back view looks evenly centred. After doing that i installed it back to the compression fittings and just slightly tightened with spanner and it seems to be ok so far.

Surely they could have machined it so that the nut always stays centric rather than wobbling about and dislodging the washer which ends up then pulling the washer into the threads

 

[avonmouth]

So I’ve managed to make it work without leaking so far. Keeping an eye on it for the next 24hrs see how it goes. But definitely think it’s very poorly designed. I had to completely removing it and have someone hold the two fittings 100% straight while hand tightening the nut. Making sure the back view looks evenly centred. After doing that i installed it back to the compression fittings and just slightly tightened with spanner and it seems to be ok so far.

Surely they could have machined it so that the nut always stays centric rather than wobbling about and dislodging the washer which ends up then pulling the washer into the threads

I fitted a chinese made, woodburner with back boiler once,and the fittings were that same as yours....ecentric.I had to use a load of hemp to make it seal properly..