Help on getting a water tight fitting

Forgive my ignorance.

I was performing a test of a new manifold today, using mains water pressure to the 22mm flow pipe and back through the return. Unfortunately it failed as one of the joints where the 22mm copper pipe connects to the manifold failed and water leaked out.

I'm now wondering (as I did when I assembled the manifold) if there are some washers missing or if I need to use a different method to connect these fittings.

First a few photos in the hope this shows what I'm talking about.

Here's the manifold, with the 22mm flow and return pipes at the bottom. Note: The valves above these are turned off.

Looking more closely at the two valves, there is an adapter that fits between the valve and the 22mm pipes, with a compression fitting on the pipe side and a sharp thread on the other side, which screws into the valve. It was this screw joint that leaked. Here's a close up photo.

This didn't come with any washers, unlike most of the other fittings on the manifold and I'm beginning to wonder if it should have. Inside the valve is a large flat area in which a washer would sit nicely, however the end of the thread (facing upwards) is slightly bevelled and a little rough, so not ideal for fitting against a washer (or is it?). The other end of the valve, which screws into the manifold, does come with a washer:

In your experience does it look like washers should be used for this "reducing" male to male fitting (I think that's what it is), or should it be fitted with lots of PTFE? I did try plastering it with Fernox Water Hawk jointing compound when I first assembled it, but clearly that didn't work!

This type of screw fitting reminds me of the radiator fittings that need to be plastered in PTFE to have any chance of not leaking.

 

Think you answered your own question there.....

You don't need lots of PTFE tape on a joint a few turns in the same direction of the thread will do

 

Thanks, I've now used PTFE along with some Delta 333 pipe sealant I had lying around. On the first one I wound around 5 turns, but it still didn't feel particularly tight, so for the second I wound around 9 and it was much tighter.

I'll try another pressure test today. Fingers crossed as I really don't trust these type of fittings, in fact why do they make none-water tight fittings for use in an environment that requires water tight fittings? I just don't get it!

 

Doh! Still leaking, although it is much better than it was. So maybe 5 turns of PTFE tape wasn't enough!

 

Used Loctite 55 (probably more than I should) and just tightening up the joints I could feel the difference.

Mains pressure test shows they are now water tight.

I will be using Loctite 55 from now on