Anyone know how to size the thread on very old seacock gate

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MikeCarr

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I have removed the inlet middle part of a gate valve(stuck but not now)the male taper thread is in very poor condition and will probably leak when open ptfe wont work o rings too large I cant seem to size the thread or the valve. It is fitted as inlet to Simpson Lawrence heads on a 25 year old boat. A very large Stilson removed it but made a mess of middle . Any ideas where to replace it otherwise skin fittings are good and I am reluctant to change them or use a lot of goo as when I launch it would be very awkward to stop a big leak I live too far away from Beaulieu /forums/images/graemlins/confused.gif
 
Some idea of the size (diameter) of the hole that the tap 'handle' fits into and maybe the pipework size please.

Depends on size but I may have one in the shed.
 
I am not at all sure what part you are concerned about. The thread between valve and skin fitting will most likely be BSP if it is British. Diameter and thread pitch will go a long way towards identifying it.

Threads on the valve internals may well be non standard but again diameter and pitch and form may help to identify it. I cannot picture a taper thread inside a gate valve!

I think your best option is a new valve. Compared with seacocks gate valves and ball valves are not expensive.
 
If you are really stuck and unable to find the part you need then reply with your E-mail address so that we can get in touch. I may be able to make the part you require. I am not a company but have the necessary in my workshop. I shall be away until the 20/5/2008
 
Thanks will check after weekend it is the handle and gate part of the valve. getting a new valve means changing the skin fittings too I think and the pipe work watch for dimensions if poss thanks to all Mike
 
I have found a solution, the valve is a butchered 3/4in gate valve screwed on to a S&L skin fitting. It was so old it looked as if it was one piece. Strangely the inlet and outlet threads were parallel threads. I have replaced the old valve with a new valve from BSS (£30) the new valve has both females with a taper thread and with ptfe fit well .The central part of the valve, the gate was damaged anyway and could not seat correctly hopefully the skin fitting will hold as it is very corroded but if not wont be so difficult to replace now . Are all females taper and males parallel? thanks for your help Mike /forums/images/graemlins/grin.gif
 
[ QUOTE ]
Are all females taper and males parallel? thanks for your help Mike


[/ QUOTE ] Among most common plumbing fittings female threads are parallel. Male thread may be parallel or tapered.

Parallel to parallel fittings are usually designed so that they screw down onto some sort of joint washer. Common practice with plumbing is for a parallel female threaded fitting such as a valve to be screwed onto a tapered male thread and for the joint to be sealed with a joining compound or tape.

Having said that skin fittings are parallel threaded because the nut has to be screwed all the way along it. That can make it difficult to make a good seal into a parallel female thread. The use of a back nut to secure it and jointing compound to make the joint water tight is the solution there but if the valve or whatever has a tapered female thread so much the better perhaps.

For precision engineering such as high pressure hydraulics etc tapered to taperd threads are used or parallel to parallel but in common plumbing stuff I don't recall ever seeing a tapered female thread but I probably have.
 
Thanks Vic I must have misunderstood the salesman my new valve almost certainly has a parallel female thread. It just dosent screw all the way down like the old one.The skin fitting definitely being parallel male and incidentally the outlet to hose connector too is parallel.
Hopefully when I hit the water all will be well and watertight. Thanks for your help Mike
 
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