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Connecting to 3/4" threaded female end on rising main

Postby Nic888 » Thu Sep 16, 2021 1:03 pm

I wonder if anyone can help, I've tried several plumbers merchants to no avail. I have removed an old stopcock, (which seized long ago, with a newer stopcock just above) as it had been leaking from several places, mainly at the bottom where it joined the 3/4" threaded female end on rising main.

I've replaced the newer stopcock above with a brand new one, and piped down to the top of the main pipe. Then connected it using a brass 3/4 iron male to 15mm pipe compression fitting.

The male fitting screwed nicely into the female 3/4 nut on the end of the supply pipe. However, when tightened, it is still wobbly because the internal narrowing inside the brass fitting is too deep in the fitting, and when tightening the female nut , the narrower part isn't reached, so nothing to tighten against.

This is because on the end of my supply pipe is a fixed ridge or lip which the female nut pulls on as tightened (rather than an olive which naturally slides in to the correct position as tightened). This means I need a much shallower brass fitting to be able to tighten it up, and also with a smaller inside diameter.

I have temporarily got around this using two O rings seated in the bottom of the inside of the new brass fitting, which both makes it internally shallower and reduces the diameter, and all can be tightened and water is now back on.

But, not surprisingly. there is a weep coming from the bottom of the old female 3/4" nut. I've tried PTFE and also Boss white but still the weep. I understand why the weep is there.

Firstly - does anyone know of a 3/4 male iron fitting with a much shallower internal depth and also a smaller internal diameter?

This would replace my temporary standard one and the O rings. However it may still weep from the bottom of the old female iron nut, since the stopcock I removed had the correct (shallower) fitting on it but still wept from the bottom of the nut.

Secondly - I would like to replace the female nut on the end of the main, but can't because of the lip. It may be possible to cut off the lip and then fit a standard compression fitting with and olive so it can tighten up fully, as a standard brass fitting.

Trouble is , the pipe looks like iron, and in any case below the lip may not be 15mm, though it looks quite close but slightly bigger, and I can't try any (brass) olives or fittings as the lip is there. Also cant get in to cut it, as we are at ground level. (could be done if it was copper with a small pipe cutter) . And the pipe end it has that strong lip for good reason!

Is there any way around this other than cutting the pipe below the end?

Is there a way to stop the weep from the bottom of the female nut?

Please see photos. All help would be appreciated very much !
The lower end of the old stopcock removed. Fitting needed the same as this - shallower internally than the standard new brass 3/4 inch iron to 15mm compression fitting.
New 3/4 male to 15mm pipe compression fitting in place.
IMG_0896.png (469.4 KiB) Viewed 117 times
Showing the (iron?) pipe end with lipped end, with female 3/4 nut dropped. (old stopcock still in place)
IMG_0895.png (461.91 KiB) Viewed 117 times
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Simply Build It

Postby stoneyboy » Fri Sep 17, 2021 8:54 pm

Hi nic888
Suggest you buy a 3/4 iron nipple and see if this will fit. If it’s ok then get a 3/4 female to 15mm copper adaptor.
Regards S
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Joined: Wed Dec 10, 2008 6:44 pm

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