Fiber or PTFE

[mike os]

Parallel thread face seal fittings are generally high pressure, and can still be sealed with ptfe.

Thet will always have very clean machined faces

 

[Maker]

All look like straight threads to me:

View attachment 343556

View attachment 343557

View attachment 343558

Experience tells me they all benefit from thread sealing though. The non-return valve (not shown) has no shoulder to seal a washer to.

The plastic one is a compression fitting, the threads don't provide the seal so it doesn't need anything on it. The second one already has a silicone gasket that'll seal so again no need for anything. The last fitting looks like it does need some sort of sealant.

 

[Prajna]

The plastic one is a compression fitting, the threads don't provide the seal so it doesn't need anything on it. The second one already has a silicone gasket that'll seal so again no need for anything. The last fitting looks like it does need some sort of sealant.

Thanks Maker.I tend to use a wrap on the plastic ones anyway, just to lubricate the threads when tightening them up. The second pic is a sacrificial anode for inside the bailerina, connected to a stainless thread.