Skin Fitting and Sea Cock

donncha

donncha

Well-Known Member
Joined
9 Nov 2007
Messages
119
Visit site
I have just installed a 1" skin fitting with a 1" sea cock(standard both sides female) for the raw water intake for the engine, replacing a rusty old gate valve. The hose for the filter and engine raw water pump is 19mm. I can't find any hose connection which will allow me put a 19mm hose on a 1" sea sea cock.

Question 1)
The female fitting on the sea cock is a standard 1" parallel female. Is it possible to put a tapered 1" male into this or must you use a parallel?

Question 2)
Is these any standard parallel 1" male fitting that will take a 19mm hose?

Question 3)
If I can use a tapered male fitting would these two work together to provide what I want?

BRASS HEX BUSH 1 INCH MALE x 3/4 INCH FEMALE - BSP Male Taper Thread: ISO 7/1 (BS 21) Female Parallel Thread: ISO 228/1 (BS 2779),

BRASS CONNECTOR STRAIGHT WITH FLANGED HEX SHOULDER BSP PARALLEL MALE THREAD 3/4 INCH BSP - 20mm HOSE
442HSE78002

Can be found:
http://www.chandleryworld.co.uk/acatalog/BrassPipeFittings.html
http://www.chandleryworld.co.uk/acatalog/BrassStraightFlangedHexBSPPMT.html

Thanks
 
Vetus make a stepped pillar that will reduce from 25 to 19 mm part no HA 1338 which you can put in your pipe run.
 
1. If the face of the valve around the thread is a decent flat surface it would be preferable IMHO to use a fitting with a parallel male thread and a shoulder that tightens down on to a joint washer (or O ring possibly). You may however find that you will have to use a tapered male fitting and ptfe tape. It is common plumbing practice but some will argue that tapered and parallel fittings should not be used together. They wouldn't be in some industries.

How is your new valve threaded onto the skin fitting? Parallel to parallel but without a joint washer, just relying on lashings of tape ... ugh!

2. Try a decent plumbers merchant for fittings or take a look at www.BES.co.uk or is it something A.S.A.P. will do

3. yes they look like a way of doing it if you cannot get the hose tail with the right size thread.


It would be better if you could get then in dezincification resistant (DZR) brass. I hope your skin fitting and new valve are DZR if not bronze
 
The skin fitting is bronze with a nickel plated brass ball valve. There is plenty of PTFE tape used between the two. What kind of "joint washer" should I use?

It would seem that BES have brass reduction brushes that I could use. (1" male to 3/4" female) both parallel. There is a plumbing shop down the road I could give a try. Would I be much better off using a bronze valve and all bronze fittings there after? Or would brass fittings do?
 
Don't use brass - DZR brass if you can't find anything better. The web site you originally quoted does a DZR brass 1"BSPT to 3/4" hose barb(should be OK for 19mm hose) about half way down this page.

I don't believe male taper into female parallel is a problem - it's the way a hell of a lot of pipework is made up (most female threaded fittings are parallel, and male fittings are tapered - often made up on-site with a pipe-threading machine that produces tapered threads). Unless you're talking high pressure hydraulics, or other exotics, you will need to use something for thread sealing, anyway - PTFE, sealant, or hemp & Boswhite /forums/images/graemlins/smile.gif.

The problems arise when you've got two parallel threads without a sealing face. I think that the best you can do where the valve joins the through-hull is to find a 'back nut' which screws onto the through-hull before the valve, and can be tightened against the valve when it is in position - if the end of the valve is machined, it might be worth putting a sealing washer between the two (usually fibre??), but as there's nothing sealing the nut against the thread, this isn't going to keep things watertight without the "loads of ptfe tape - eugh" over the end of the through-hull. (I don't like it either, but I don't know of a better way with this sort of arrangement).

Sorry, wrote more than I intended !

Andy
 
Ordinary brass tends to dezincify that is it loses the zinc that is alloyed with the copper The copper remaining has virtually no strength.. It is characterised by a pink colouration.

Bronze is a copper/ tin alloy that does not suffer in the same way. DZR brass is a leaded high tensile brass that is also heated treated I believe. Not quite as good as bronze ,but a bit cheaper, and way better than ordinary brass.

Avoid ordinary brass definitely.

The joint washers i was referring to are flat washers (just like a washer you'd put under a nut) made of a fibre jointing material that means they have to be between two flat surfaces.
 
Thank's very much for the help. I'll give my local plumbing shop a visit first though before buying online because the total comes to about £45inc postage. I think I'll go for all bronze in the end if I can afford the valve. What I am planning on is

HOSE CONNECTOR BSP TAPER MALE THREAD 1 INCH BSPT - 3/4 INCH HOSE

ISIS DZR (or bronze) BRASS BALL VALVE 1 INCH BSP

+a couple of heavy duty backnuts and fibre washers.

I already have the skin fitting installed and I have plenty of PTFE tape. Have I left anything out?

Thank's again
 
[ QUOTE ]
+a couple of heavy duty backnuts and fibre washers.

[/ QUOTE ]

I think you only need one backnut: to tighten against the valve when it's threaded onto the through-hull - the tapered hose-tail will (should) tighten up into the valve OK.

Incidentally, there's no problem using a 'bush' to match a smaller male thread into a larger female one - that's what they're made for - but if you can get it all in one fitting, then all the better.

By all means use a fibre washer, but (with due respect to VicS) I don't think it gains you anything in this case - if there was a machined face on the end of the valve sealing against a machined shoulder on a fitting with a washer in between, then fair enough, that's the way parallel fittings are supposed to work. If the valve is against a backnut, then the washer *may* seal the valve and nut together, but unless you add some goop (e.g. PTFE) to the threads, the nut/valve combo will still leak along the threads. At least, by adding a backnut, you can force the threads into close engagement, and lock the whole thing together to give it some mechanical strength.

Apologies if this crosses over a reply from VicS / only succeeds in complicating matters /forums/images/graemlins/smile.gif

Andy
 
[ QUOTE ]
By all means use a fibre washer, but (with due respect to VicS) I don't think it gains you anything in this case

[/ QUOTE ] I was meaning a fibre washer on fittings with parallel to parallel threads and mating faces tor the washer.

I too was wondering about a back nut on the skin fitting to lock up agaist the valve body. (agreed although a fibre washer there is not going to serve much of a useful purpose.) I think it would be a good idea though as it will lock the valve body firmly in position. To do it up against the valve body tightly there will have to be not to much surplus tape on the thread though.

So then valve screwed onto skin fitting with tape to seal the joint and a back nut to stop the valve turning on the skin fitting, Hose tail screwed into valve with tape.

Hose secured to hose tail with two stainless steel Jubilee type clips

BTW wind the tape on the male threads in the same direction that the female thread will screw onto it or else you'll unwind the tape as you screw them together.
 
You must log in or register to reply here.

Share this page

Top