To PTFE, or not to PTFE?

[Michael Kilpatrick]

Hello all,

I've just inserted a solenoid valve in a run of Hep 15mm pipe to the water inlet of the toilet header tank - this is part of my home-made control system for the feed from the rainwater harvester tank (under the patio) to provide the toilet flush water.

Solenoid valve:

question is this: given that the valve has 1/2in BSP threads in plastic, and that the easiest way of fixing the valve appeared to be get this metal BSP-to-15mm-compression adaptor:

I, by default, always use PTFE tape between the metal female BSP thread and the male plastic BSP thread of the solenoid valve?

Or are such things designed to seal properly without such assistance? Yes, there's a rubber washer inside the adaptor.

I'm just suspicious of these horrible plastic body threads, like those on dishwashers and washing machines, which I always seem to have problems with!

The compression fittings I think are fine. Yes, before anyone asks, I did use the pipe inserts to do it properly when compression-fitting to a Hep2O pipe. Although I won't guarantee not having overtightened - I'll tell you tomorrow if the hallway is flooded...

Michael

[fred]

In article , Michael Kilpatrick writes

Excellent, the new RS site let's you link directly to a part!

Looks like both are intended to seal to the flange with the rubber washer so I wouldn't use tape. Without instructions to the contrary in the product data I would lightly smear both sides of the washer with silicone grease (not sealant) before assembly.

Not a bad price for bits either, RS used to be a lot more expensive for this sort of stuff.

[Heliotrope Smith]

Michael Kilpatrick wrote in news: [e-mail]:

As there is a washer supplied with the FI adaptor then that would be sufficient for the job. If you don't trust the washer alone then you could put a few wraps of tape on the male thread but don'nt over do it.About eight turns would be enough. You should rough up the thread first with a file or hacksaw blade.

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[Michael Kilpatrick]

[fred]

[e-mail] ---

Glad you're sorted.

Whatever you do I would not rough up anything.

[DerbyBorn]

On 09 Apr 2012, you wrote in uk.d-i-y: view.co.uk:

Smooth, clean and lightly lubricated is the best principal. If the face is intended to be the seal then don't put anything on the thread. Usually only tapered thereads perform a sealing role. Washing machine and compression fittings do not use the tread for sealing purposes - the thread serves to pull things together.