Gerry
Well-Known Member
Has anyone experience/advice on doing this? This is a seacock is for the shower drain pump outlet and discharges above the water line. Is there any reason that I can't just screw them together with PTFE tape?
Combining Marelon valves and bronze skin fittings.
- Thread starter Gerry
- Start date
pvb
Well-Known Member
Can't see any problem with that.
30boat
N/A
Just be careful with the torque.A bronze fitting can easily chew the threads on a plastic one.
David2452
Well-Known Member
You do need to be careful as some Marelon seacocks have bespoke threads to match their trough hull. Don't buy a through hull with valve and discard the skin fitting for that reason, however Forespar also manufacture valves and hosetails in BSP. I have used the Marelon BSP threaded valves and hosetails direct to bronze fittings with no issues, however I would never use PTFE tape on anything other than BSPT threads not BSPP.
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VicS
Well-Known Member
The Marelon threaded valves David mentioned above are designed to be used with bronze or stainless steel thru-hulls.
see http://www.forespar.com/products/boat-marine-plumbing-ball-valve-thru-hull.shtml
see http://www.forespar.com/products/boat-marine-plumbing-ball-valve-thru-hull.shtml
Tranona
Well-Known Member
Not sure why you would want to do that - but you may find the Tru Design composite valves and fittings more suitable. However the simplest replacement is a DZR valve, although above the waterline that is not critical.
GrahamM376
Well-Known Member
TruDesign composite and dzr/bronze etc. all fit together perfectly.
jakeroyd
Well-Known Member
I've done this without any issue or any issue foreseen in the future.
DZR skin fitting with Marelon seacock.
Sealed with Sika 291i
It's the loo waste , which seized up like they do.
My theory is that a resin one won't.
Can't see an issue , there is not going to be any galvanic action etc.
DZR skin fitting with Marelon seacock.
Sealed with Sika 291i
It's the loo waste , which seized up like they do.
My theory is that a resin one won't.
Can't see an issue , there is not going to be any galvanic action etc.
Gerry
Well-Known Member
Many thanks for the advice. Had no problem with the threads and used ptfe tape for a secure fit.
I am replacing two nasty ball type valves that controlled the shower outlets just above the water line. I guess this could be termed overkill but when I removed the old ones they were badly corroded- boat is 25 so not really a surprise! Anyway hopefully the new ones will give many years of good service.
Cheers guys!
I am replacing two nasty ball type valves that controlled the shower outlets just above the water line. I guess this could be termed overkill but when I removed the old ones they were badly corroded- boat is 25 so not really a surprise! Anyway hopefully the new ones will give many years of good service.
Cheers guys!
KellysEye
Well-Known Member
>A bronze fitting can easily chew the threads on a plastic one.
Marelon is not plastic it's a very hard material made of nylon and GRP.
Marelon is not plastic it's a very hard material made of nylon and GRP.
30boat
N/A
Is it harder than bronze?
VicS
Well-Known Member
How then do you define plastic if it excludes Marelon?
30boat
N/A
There's a difference between strength and hardness.Bronze will be harder than Marelon even if it's not stronger which I doubt anyway.
pvb
Well-Known Member
Not strictly true, it's a nylon-type resin (DuPont Zytel) with glass fibre reinforcement, rather than GRP.
Sam Sailing
Member
Check thread compatibility. Marelon might have American standard UNF thread and bronze skin fittings normally have metric threads as they are often made in one foundry in Italy.
30boat
N/A
Don't think so. Pipe fittings have BSP threads.
Apparently there is also the NPT thread on American fittings available from ASAP.
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Sam Sailing
Member
It is dangerous to assume that the skin fittings and seacocks have the same thread.
Forespar are American and use NPSM thread.
http://www.forespar.com/products/boat-marine-plumbing-ball-valve-thru-hull.shtml
You can specify BSP thread but don't assume. I have known of people to buy Forespar seacocks off eBay and found that they don't fit the boats skin fittings. Plus worse still, the diameter of the through hull hole will be slightly different!
Most skin fittings here are BSP but not all! Never assume anything and so its best to check first.
NPSM stands for National Pipe Standard Mechanical thread, otherwise known as Standard or American Standard.
Americans don't use BSP skin fittings.
ASAP Supplies are an excellent company. They are very knowledgeable and will make sure that you have the correctly specified BSP thread to match your skin fittings.
Having said all that, skin fittings are relatively cheap compared to the price of the seacocks so its a no brainer to me to replace the skin fittings at the same time.