AnonymousBosch

Connecting a check valve to 25mm alkathene

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Have  look at this please .....

20190911_110110.thumb.jpg.f062448728f5eb427e3ed8d5b4cd9668.jpg

 

Don't I need some sort of seal  / O ring in the brass check-valve?

Ian

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PTFE tape, wrapped tightly around the male thread, in more layers than you think it will need.

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Is the plastic fitting tapered? Six wraps of ptfe, wrap in the direction that you screw in so that the tape feels like it is tightening on the male thread as it is being assembled. If that makes sense. Sorry if stating the obvious.

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11 minutes ago, SiBee said:

[...]

Sorry if stating the obvious.

 

Nothing is obvious to me, nothing: until I've got it wrong three times and learned the hard way.

 

No, the plastic fitting is NOT tapered. What difference (tapered or not)  does that make?

The brass fitting is tapered a bit, though.

 

Thanks both.

Ian

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32 minutes ago, AnonymousBosch said:

No, the plastic fitting is NOT tapered. What difference (tapered or not)  does that make?

The brass fitting is tapered a bit, though.

I have only ever connected parallel to parallel thread or tapered to tapered not sure what would happen in your case. Would be a good experiment although it may not end well.

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I've not seen a tapered MDPE threaded connector, TBH, and I doubt the female thread in the NRV is BSPT, it's almost certainly just a standard parallel BSPF thread.  The taper on a BSPT thread is pretty obvious to look at.  We have a few of them around and all had parallel threads.  Most needed more wraps of PTFE then I'd have thought necessary, as they are often a bit tight to screw in initially, then ease up a bit as the PTFE beds down.  I don't think I've had any problems with any of them ever leaking, though.

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40 minutes ago, JSHarris said:

I've not seen a tapered MDPE threaded connector, TBH, and I doubt the female thread in the NRV is BSPT, it's almost certainly just a standard parallel BSPF thread.  The taper on a BSPT thread is pretty obvious to look at.  We have a few of them around and all had parallel threads.  Most needed more wraps of PTFE then I'd have thought necessary, as they are often a bit tight to screw in initially, then ease up a bit as the PTFE beds down.  I don't think I've had any problems with any of them ever leaking, though.

 

I bought some ball valves which were listed as being BSP and when they turned up were BSPT. When I asked the company they said their default was BSPT so they were listed as BSP and they would have been listed as BSPP had they been parallel. I was surprised as I thought BSP meant BSPP so I always check now.

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