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When fitting a Blakes seacock, or come to that, any other seacock to the through the hull fitting of a boat, what method of sealing should one use. The through hull component is metal, possible brass. Can P.T.F.E. tape be used or is there a recognised sealer or method of sealing?
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I have always used sikkaflex and have never had one leak
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PTFE tape can be used on the thread to lubricate the fitting of the nut, a mastic sealant such as Sikaflex should be used under the flange of the fitting to seal it to the hull. Snug the fitting up until the sealant has squeezed evenly across the face of the flange and allow to cure (advice on cure time as per manufacturer's instructions) before final tightening. Do not tighten down and squeeze all the sealant out!
Rob.
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Thank you both for the info, Sikaflex, seems to be the answer to most boat sealing situations! I have a further problem in that I have to replace a seacock which is not a blakes, it is a straightforward gate valve which I have now removed and intend to replace with a ball valve. The ball valve needs to be mated to the threaded 1" BSP through the hull fitting. The ball valve of course, also has a 1" BSP thread. Is it usual to use PTFE tape to seal the threads in this situation as one would do in a domestic plumbing situation or is there a more recognised or suitable method for sealing in the marine situation?
dwjc (i.e. David)
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Location: Home: Kent; Boat : Chichester
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Ptfe tape is commonly used on plumbing fittings where the male thread is tapered and the female thread is parallel.
You will undoubtably have two parallel threads which will not lock together like tapered threads. You may require a number of turns of tape to make the fitting watertight and the two will never really be positively locked together. Parallel threaded fittings should normally have a shoulder on the male part and the female part should tighten down on to that with a fibre washer or similar between them to make the water proof seal.
The best option for you, I think, is to screw a back nut onto the skin fitting and to tighten the new valve and that together to lock the valve in the position you require to allow the handle to be accessed easily and to turn without being obstructed in any way.
The thread will still need sealing and a thread sealing compound or even Sikaflex will be the way to do that.
You may be able to get a back nut from the same source as the valve, a plumbers merchant will have brass ones, or you will be able to get one and the valve you require from ASAP Supplies Ltd http://www.asap-supplies.com/
You may find the YBW boating forums useful in particular Practical Boat Owners Reader to Reader forum for advice on practical matters http://www.ybw.com/forums/index.php
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Do not put taper male fittings into parallel females, ptfe or not, both parts should be taper cut, usually used on gas type fittings...this practice is dangerous.
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Thank you both for that information, now understand the mechanics of the situation and can act accordingly.
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