Marelon seacocks - Sikaflex or PTFE between through-hull and seacock?

Hi all - give the relevance I’m trying this rather than new thread…

We launched on Tues and one (of 6) new Tru Design through-hulls is weeping between the ball valve and the skin fitting. It’s to the tune of about a pint an hour. It was sealed with Loctite 5331.

Seeing as we’re very much hoping to re-seal either with a bung in the skin fitting or during a quick ‘racing lift’ (41’ AWB so can’t dry out!), what sealant is most likely to cure for service in an hour or two?


Are we stuck with PTFE - or might Sika, PU40, OB1 etc. not mind the re-immersion? (I otherwise have stock of and trust all three!)

TIA
 
Graham376 said:
I used Hawk White thread jointing compound on our True Designs, none have leaked. That or some other plumbing sealants would most likely work OK.
Click to expand...
...I particularly like that instructions/opinion on the Hawk compound seem to suggest anywhere between 'straight away' to 1 hour for service (and even spray with water to speed cure!).

I do wonder if the polyurethane spodge would take so kindly to being immersed so quickly and under reasonable pressure?

I accept that we were just unlucky with that one leak, not least as the other 5 fittings (inc. another 1 1/2 inch - which the leaky culprit also is) seem to be dry as a bone so far.
 
dankilb said:
Hi all - give the relevance I’m trying this rather than new thread…

We launched on Tues and one (of 6) new Tru Design through-hulls is weeping between the ball valve and the skin fitting. It’s to the tune of about a pint an hour. It was sealed with Loctite 5331.

Seeing as we’re very much hoping to re-seal either with a bung in the skin fitting or during a quick ‘racing lift’ (41’ AWB so can’t dry out!), what sealant is most likely to cure for service in an hour or two?


Are we stuck with PTFE - or might Sika, PU40, OB1 etc. not mind the re-immersion? (I otherwise have stock of and trust all three!)

TIA
Click to expand...

Loctite 5331 is relatively low strength and designed for joining plastic water pipe threads. It seals quickly. It's what I used between TruDesign and ball valve when fitting a new TruDesign seacock between tides (CT1 for the through-hull). So it shouldn't be difficult to take apart and fine to re-treat. I probably over-applied just to make sure. Your problem would simply have been an error in application.
 
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Poey50 said:
Loctite 5331 is relatively low strength and designed for joining plastic water pipe threads. It seals quickly. It's what I used between TruDesign and ball valve when fitting a new TruDesign seacock between tides (CT1 for the through-hull). So it shouldn't be difficult to take apart and fine to re-treat. I probably over-applied just to make sure. Your problem would simply have been an error in application.
Click to expand...
Yup I agree. I stuck probably too steadfastly to the instructions to apply only to 1/3 circumference of the first 4 threads… seemed to work perfectly up to 1” BSP (inc some reassuring squeeze out) but just failed on that one larger fitting.

Silly really as if it had been a PU/hybrid sealant I’d have covered all threads and cleaned up the mess instead of being stingey!
 
dankilb said:
BTW the skin fittings are epoxied so at least that should reduce any risk of it moving on disassembly
Click to expand...

If I was doing it while afloat I'd try to find a way of securely attaching a short length of line to a rag that can be stuffed into the through hull, then remove old ball valve, plug the through hull with rag quickly, dry the threads, apply sealant, lead line through the new ball valve then tighten down and position, pull out the rag plug starting with the end of the line, and shut the valve and mop-up. You may not stop all the water but should avoid the initial gush which could wash off the sealant.

Or plug with a thick absorbent paper plug (like paper towel) and eliminate at the end by poking it out with a stick.
 
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Poey50 said:
Loctite 5331 is relatively low strength and designed for joining plastic water pipe threads. It seals quickly. It's what I used between TruDesign and ball valve when fitting a new TruDesign seacock between tides (CT1 for the through-hull). So it shouldn't be difficult to take apart and fine to re-treat. I probably over-applied just to make sure. Your problem would simply have been an error in application.
Click to expand...
5331 is the stuff to use. It actually allows for adjustment for a few hours after assembly. It is very good on TruDesign fittings which tend to have fairly loose fitting threads for which sealant is better than PTFE tape. I used it on all my TrueDesign parts.
 
Poey50 said:
If I was doing it while afloat I'd try to find a way of securely attaching a short length of line to a rag that can be stuffed into the through hull, then remove old ball valve, plug the through hull with rag quickly, dry the threads, apply sealant, lead line through the new ball valve then tighten down and position, pull out the rag plug starting with the end of the line, and shut the valve and mop-up. You may not stop all the water but should avoid the initial gush which could wash off the sealant.

Or plug with a thick absorbent paper plug (like paper towel) and eliminate at the end by poking it out with a stick.
Click to expand...
I hadn't actually thought of ways of sealing from the inside - but the rag/line tip is particularly ingenious... Luckily (not for him?!) a colleague has offered to dive on it and we plan to try bunging it from the outside with a softwood bung wrapped in amalgamating tape. (By 'dive' I really mean put on a winter wetsuit and float around - but it's a couple of feet below the waterline and less effort than trying to get the dinghy out and inflated even!)

Norman_E said:
5331 is the stuff to use. It actually allows for adjustment for a few hours after assembly. It is very good on TruDesign fittings which tend to have fairly loose fitting threads for which sealant is better than PTFE tape. I used it on all my TrueDesign parts.
Click to expand...
Good to see plenty of votes for 5331, so it sounds like the rest of the fittings (sealed with the same) aren't doomed!

We might initially try again with the 5331, having noticed the TDS does promise an instant seal to 0.05mpa (7-odd PSI). That way, presuming we keep the bung in for half an hour or so (aforementioned diver can go for a swim!), we should be good.

Otherwise it'll be on to the Hawk White for its promised instant seal 'for service'...

Thanks all. I was concerned the consensus might be 'don't touch it' - but glad it seems it can realistically/safely be re-sealed.
 
I was advised to use Sika 291 to on both the through-hull to hull bond, and threads of seacock to through-hull. Has worked ok.
 
Our true design valves are leak free with PTFE (couldn't find the 5311 where we were at the time). Lots of wraps though.

Another time I successfully plugged a through hull with a trimmed down potato before changing a valve. Can be easily trimmed to size then jammed in to form a really good seal.
When your done poke a stick through the open seacock to get it out.
Try it if you struggle get the wooden bung to seal.
 
Dantp said:
Our true design valves are leak free with PTFE (couldn't find the 5311 where we were at the time). Lots of wraps though.

Another time I successfully plugged a through hull with a trimmed down potato before changing a valve. Can be easily trimmed to size then jammed in to form a really good seal.
When your done poke a stick through the open seacock to get it out.
Try it if you struggle get the wooden bung to seal.
Click to expand...
It might be the first and only time I take a single potato to the boat - but I'll try anything!

Another one I thought of was a development of @Poey50 's suggestion by balling up a rag inside a nitrile glove and pulling that through... not a bad gasket material after all.

Lightwave395 said:
Just about to fit 4 new tru-design thru-hulls and ball valves, it'll be CT1 for the thru-hulls and Hawk white for the ball valves for me
Click to expand...
Sounds perfectly sensible to me. From the position I'm in - anything sounds good that doesn't involve too much bond strength on the ball valve (like proper jointing/pipe sealing compounds). I'd be looking forward to the job less if I'd used a stronger sealant-adhesive on the valve threads.
 
superheat6k said:
when bedding in the fitting I do not pull the fitting up hard to the hull but leave a small gap ~ 2mm to allow the sika to form a gasket between the fitting and the hull then after a few days pull the joint up, as this provides better flexibility in the overall fitting, that a thin film of sika will not provide..
Click to expand...
That's always worked for me too.

Www.solocoastalsailing.co.uk
 
Dantp said:
Our true design valves are leak free with PTFE (couldn't find the 5311 where we were at the time). Lots of wraps though.

Another time I successfully plugged a through hull with a trimmed down potato before changing a valve. Can be easily trimmed to size then jammed in to form a really good seal.
When your done poke a stick through the open seacock to get it out.
Try it if you struggle get the wooden bung to seal.
Click to expand...
We have a Seabung: Seabung

.
 
The main features of the method used to temporarily block the through hull in order to fit the ball valve is first that the blockage should not prevent the ball valve being fitted (so tapered bungs are out) and second that the blockage can quickly be removed.

Having first suggested the rag on a line method I think that a thick paper towel (hand towel or industrial blue paper wipe) might be more suitable. I accidentally blocked a through hull on my new holding tank installation with a plug of paper (I had left in some blue paper towel in the tank connectors to prevent rubbish getting in) and was impressed what a sold blockage it made. Paper swells up fairly quickly and should then hold. A stick would quickly poke it out from the bottom whereas a rag on a line could get caught being hauled out, or the line break etc.
 
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dankilb said:
Hi all - give the relevance I’m trying this rather than new thread…

We launched on Tues and one (of 6) new Tru Design through-hulls is weeping between the ball valve and the skin fitting. It’s to the tune of about a pint an hour. It was sealed with Loctite 5331.

Seeing as we’re very much hoping to re-seal either with a bung in the skin fitting or during a quick ‘racing lift’ (41’ AWB so can’t dry out!), what sealant is most likely to cure for service in an hour or two?


Are we stuck with PTFE - or might Sika, PU40, OB1 etc. not mind the re-immersion? (I otherwise have stock of and trust all three!)

TIA
Click to expand...

Maybe these links could be helpful?

Thru hull ball valve leaking - The Hull Truth - Boating and ...
https://www.thehulltruth.com › ... › The Boating Forum

15 May 2005 — The Boating Forum - Thru hull ball valve leaking - Put the new boat in the water last weekend, checked all the thru hulls for leaks.
thru hulls are leaking. advice needed 17 June 2012
Leaking Thru Hull Valves - Boating and Fishing Forum 3 Feb 2014
HELP, my thru hull is leaking around the fitting 1 Apr 2006

Seeping thru hull valve | Sailboat Owners Forums
https://forums.sailboatowners.com › ... › Ask All Sailors

8 Nov 2011 — Leaks don't mysteriously disappear and it is going to get worse not better. The constant water flow for the a/c will add to the leak. Sealers or ...
Mystery Leak: Do Thru-Hull Sea-Cocks Leak? - Sailboat ... 31 May 2007
Fix a Thru hull seacock in the water? | Sailboat Owners Forums 24 June 2009
Raw Water Intake Ball Valve won't close! - Sailboat Owners ... 16 June 2014
Uncooperative Through Hull | Sailboat Owners Forums 9 May 2019
 
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