Water pipe fitting size help

[conradh]

What is the name of the fitting I should be looking for to insert a pressure reducing valve under my kitchen sink, given that the pipe itself has an outside diameter of 15mm, *but* the pipe's screw fitting that I'd be inserting the PRV into has thread diameter 24.4mm-26.6mm (measuring the inside of the female connector's thread and the outside of the male connector's thread, respectively: I guess I'd call that one inch)? The most common PRV size options of 22mm and 15mm don't sound right, unless it turns out that there's some kind of convention that 15mm pipe always uses one inch threaded connectors, so "15mm" actually means a one inch connector and that's what I should go for?

Normally I'd just check the diameters matched at the hardware shop, but can't do that at the moment!

(Context: inserting this before the feed-off to the washing machine, along with a tee to an undersink filter which can't take my mains pressure.)

 

[denso13]

I'd guess you need 15mm x 3/4" male couplings. I think they measure about an 1" across the threads. Got a link to the valve?

 

[conradh]

Hi @denso13, thanks for the quick reply! I was looking at this kind of thing [Amazon UK link].

 

[dal5band]

A "15mm valve" will accept 15mm pipe at both ends, a " 22mm valve" will accept 22mm pipe - end of story ! The valve has olives and nuts, you insert clean cut pipe and tighten nut which compresses the olive onto the pipe to form a sealed joint. The size of the nuts and threads is irrelavent.

 

[denso13]

Hi @denso13, thanks for the quick reply! I was looking at this kind of thing [Amazon UK link].

You would be better with 15mm compression ends which will fit straight on to 15mm copper. Some do come with female ends which need the appropriate male coupling.

 

[conradh]

A "15mm valve" will accept 15mm pipe at both ends, a " 22mm valve" will accept 22mm pipe - end of story !.

Thanks for the clarity on that, but what I've got isn't exposed pipe, it's the screw threads of a cut-off valve which supplies the washing machine. This looks like the least effort point for inserting a tee to a small under-sink filter (and separate tap), but I also (high mains pressure) need to insert a pressure reduction valve for the filter to be happy. Putting the PRV in for the whole house rather than just here would be nice, but not an option at the moment. So I'm wanting to insert the PRV and filter tee between the one-inch male thread of the cut-off valve, and the one-inch female thread of the washing machine hose. Or to be told that the only practical solution involves more serious work than just screwing things together.

Some PRVs seem to come with (for example) "DN25" female threading, others as you point out have male threading and a nut for a compression joint. I'm just trying to work out what size of PRV and what adapters would be the least effort combination to connect

1" male thread -> (adapter?) -> PRV (15mm/22mm/DN25/???) -> (adapter?) ->
-> filter T -> (adapter?) -> 1" female washing machine hose thread

.. where for the moment I'm concentrating on the PRV since solving that will probably put me on the road to what needs doing for the filter T as well.

In a sane world there'd be a cut-off valve for the whole flat that would allow me to do this on the 15mm pipe before the washing machine cut-off valve, but there's no whole flat cut-off.

 

[cdbe]

If you haven't got a stoptap for the property you should sort this out before messing with anything else, especially trying to connect a prv to a washing machine tap. There will be an external one somewhere which you use to isolate the internal supply to allow you to fit one - once you have your internal stoptap you may find that partially closing it will achieve the pressure reduction you need.

 

[Madrab]

partially closing it will achieve the pressure reduction

Unfortunately not, a mains stop tap will not reduce the pressure that the mains will deliver, all it will do is reduce the flow ..... the static/dynamic pressure will stay the same.

 

[Jackrae]

Unfortunately not, a mains stop tap will not reduce the pressure that the mains will deliver, all it will do is reduce the flow ..... the static/dynamic pressure will stay the same.

Static pressure will remain the same but dynamic pressure will reduce due to pressure drop across the restriction of the partially closed valve. Not that that bit of info helps the OP with his problem

 

[AdrianUK]

Static pressure will remain the same but dynamic pressure will reduce due to pressure drop across the restriction of the partially closed valve. Not that that bit of info helps the OP with his problem

Thread Tangent warning....

But will a PRV reduce both the static & dynamic pressure?

Most of the (admittedly cheap) ones I've played with will only reduce the dynamic pressure.

 

[JimCrow]

Thread Tangent warning....

But will a PRV reduce both the static & dynamic pressure?

Most of the (admittedly cheap) ones I've played with will only reduce the dynamic pressure.

A "drop tight" PRV will maintain it's set down stream pressure in a no flow situation.