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

[superheat6k]

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

Just seen this, but my choice here would again be Loctite 577. It seals hot fridge systems at 30 bar, so will definitely work at 0.05 bar a few inches below water level at ~ 15 - 30 oC. Goes on in seconds and sets semi hard. Loctite sell it as a thread sealant but it works as well on re-sealing tired o rings and gaskets. However, if your leak is around the skin fitting itself then a decent face seal will be needed. 291 but will need a period to set. Butyl tape would sort this.

 

[CrossedThreads]

Loctite 5331 worked well on the threads of the nine TruDesign seacocks I fitted earlier this year. I definitely used more than “recommended” and wiped away any excess. Not that it’s relevant to the OP but maybe to others, 291 was my go to for the thru hull itself.

I think at this point it’s more about working out how to do this live, being able to stem the water flow yet have whatever is blocking the flow removed easily.

 

[coopec]

When I read the screed on Loctite 5331 they only talked about its' use on "plastic" sea-cocks.

I am using 291 on the SS thru hulls and Teflon thread tape on the SS sea-cocks.

I wonder if Teflon tape would tend to act as an anti-sieze? (A little research and it does act as an anti-seize!)

Does Teflon tape act as anti seize?
Thread seal tape (also known as PTFE tape, Teflon tape, or plumber's tape) is a polytetrafluoroethylene (PTFE) film tape commonly used in plumbing for sealing pipe threads. ... Thread seal tape lubricates allowing for a deeper seating of the threads, and it helps prevent the threads from seizing when being unscrewed.

Thread seal tape - Wikipedia

 

[Yngmar]

I've used PU adhesive sealant on skin fittings, ball valves and hosetails. Initially I had PTFE tape on the hosetails, but that was leaking on the 90 degree elbows because they inevitably rotate a bit as you wrestle the stiff toilet hose on (yes I know about heat guns and boiling water - still needs wrestling) and that was enough to cause the PTFE tape to fail as once it's compressed it can't deal with the slightest backing off. Zero leaks since the PU. If you're worried about having to swap out something later, use silicone sealant (without the adhesive) on the hose tails, it's sticky enough to keep them in place but will break if you try. The PU adhesive sealant prevents disassembly.

For the OP's problem of quick immersion after assembly, the stuffed potato idea sounds great!

 

[Graham_Wright]

We have a Seabung: Seabung

.

I met the designer at SBS one year - next stand to ours. He told me the production cost of the basic plug was £0.02.
One hell of a mark-up.

I have just bought two sink plugs for the galley. The existing one had a raised centre which was prone to being displaced thus losing the sink contents. The new ones are very floppy discs (Large Universal Silicone Drain Plug Kitchen Bath Tub Sink Cover Stopper 15cm/6” | eBay) and I wonder if a similar device could be produced with a rod or cord through the middle.

 

[dankilb]

Took a while to get around to this - especially after realising I couldn't reach the skin fitting over the tube of the dinghy (and putting someone in the water seemed like overkill!). In the end, a SUP board was deployed - with me, soon soaked, prone on top! - in order to get a full arm's length below the waterline.

Thankfully, it worked just fine. In the end, the bung of choice was, well..., a bung! Tapered softwood bung, with the end cut down so as not to foul the valve, with a gasket of butyl tape and wrapped in a nitrile glove (the glove mainly served to keep the tape attached to the bung in the cold water!).

This reduced ingress to a trickle, but with further fettling I'm sure it could have been made to seal entirely. We did try a rag balled inside a glove, but that proved harder to push into the hole (bearing in mind the paddle board didn't offer much resistance against any forced exerted and very readily/annoyingly/comically pushed away from the hull!). I reckon it would be hard if diving/swimming too, in that respect. I did take a potato down, but it was quite an unevenly shaped Maris Piper and we couldn't really do much with it (although it made it home and into last Sunday's roast!).

The valve was removed very easily. In fact, there was barely any evidence of 5331 left on it. It definitely needs more than the 'first 4 threads, 1/3 circumference' advised on the tube.

In the end, I re-sealed with the 5331 (on the basis it was working fine on the others and I could try something else if it failed again...). This time, I did half the thread depth and the entire circumference. This worked fine and first time. The bung was left in place as long as I could tolerate (bearing in mind I was soaking wet already and due for another semi-dunking!), which was maybe 15 mins, so it barely had any 'cure' time before being back under pressure.

No leaks since Saturday. (Although a new one appeared - pink this time - core plug on the back of the Beta's cylinder head! ?)

 

[RJJ]

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

I used, and strongly recommend for you and the OP, the loctite stuff that looks like dental floss. #55 if I remember right. it's on the "recommended" list in the Trudesign fitting manual.

It's an instant, effective and non-permanent seal. And you can fit it in a tight spot without spilling it and making a mess with kitchen roll etc...

If you use the right amount, it winds up nice and tight. The "right amount" is specified on the pot in terms of wraps per inch of diameter; in the case of the Trudesign fittings, the thread is on the wobbly side and seemed to call for a couple of extra wraps. Could be the same for Marelon.

If it was me, I'd apply using a bung in the hull fitting, and save the £300 or whatever a quick lift costs you.