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Old 14-06-2015, 11:13   #1
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Tips for slow seacock leaks?

I just finished a week long haul-out where I disassembled, lubed and resealed all 9 seacocks and hose barbs on our new-to-us 30-year-old boat. So I was a bit disappointed when we splashed and I ran down to check them all and 3 had slow leaks. Initially a fairly fast drip which gave me a bit of a panic, but with some tweaking I got them under control to a very slow drip.

I've read a bazillion articles and forum posts on seacocks, so I think I've about tapped out what I can learn from articles. Most articles seem to focus on basic seacock safety, and skip the little common sense things like how to deal with a slow leak at an elbow joint junction.

Any tips on how to fix these? I had slow leaks before too, so the situation isn't any worse now, but they're the only thing standing in the way of a dry bilge, which I see as a sign of a well kept boat.

Eventually I'll probably replace many of the seacocks and thru-hulls (since the backing plates were a survey issue), but not till the fall at least. I'd like to find a temporary fix for now without doing another expensive haul-out.

Exhibit A) Stbd scupper 1.5" bronze seacock with 1.5" Marelon 90 degree elbow, teflon tape sealant.

Leaking from the elbow joint threads where I placed fresh teflon tape sealant during haul-out. Frustrating since isn't this exactly what teflon tape is supposed to prevent? I did about 3 360 degree overlapping wraps.

I wonder if the seacock is NPS and the elbow NPT. Maybe should replace with a bronze elbow. But I didn't notice any threading problems when spinning it on. Is there a different non-adhesive thread sealant I could try?

Exhibit B) Port scupper 1.5" Marelon with 1.5" Marelon 90 degree elbow attached by a large cap nut and sealed with some kind of white soft adhesive sealant (prior owner).

Leaking from the sealant at the elbow to cap nut joint. I tried to unscrew this nut during haul-out and couldn't get it to move. I probably disturbed the seal a little though. Is there a better, relatively non-adhesive sealant I could try overlaying? 4200 seems too permanent.

Exhibit C) Engine intake bronze 1" leaking from seacock barrel at nut end.

This one I might not be able to fix until I replace seacocks. I cleaned and lubed it (with Forespar marelube) like all the others. Tightening the nut slowed the leak but not stopped completely. So the seacock probably needs to be relapped or is done for. I have pics of the seacock barrel.

Note: Gray PVC elbow joint is glued on to the seacock with a gray very hard glue (5200?). An unfortunate decision of a prior owner to crazy glue non-marine elbow joints on to several seacocks, and on my fall haul-out list to fix. Removing it will probably require destroying the joint and/or seacock. It's not leaking however.
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Old 14-06-2015, 11:50   #2
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Re: Tips for slow seacock leaks?

"Its not leaking, however"
Sorta tells you that 4200 could be a good choice to replace the teflon tape.
Obviously 5200 is not wanted.
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Old 14-06-2015, 11:58   #3
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Re: Tips for slow seacock leaks?

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"Its not leaking, however"
Sorta tells you that 4200 could be a good choice to replace the teflon tape.
Obviously 5200 is not wanted.
Perhaps so, but isn't 4200 still quite adhesive / semi-permanent? It appears so from my limited use of it so far, and Maine Sail says even 4200 is almost overkill for thruhull bedding (the exterior mushroom head sealant). Sikaflex is apparently a little less adhesive, but I'm still not sure about using that on elbow joint threads. I want to be able to remove elbow joints for servicing / replacement if needed, without destroying the seacock.
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Old 14-06-2015, 12:00   #4
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Re: Tips for slow seacock leaks?

I've found teflon paste to be more reliable than tape, either used together or the paste on its own.
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Old 14-06-2015, 12:16   #5
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Re: Tips for slow seacock leaks?

You need to use the appropriate number of turns with Teflon tape. This can be anywhere from 5 to 12 turns/wraps.
Thread systems vary between plastic, Marelon and Bronze. Often they don't seal well together.
For #3 /bronze seacock, I prefer Lanolin or Lanocote (will usually prevent drippage) Unfortunately you cant use that now that you are back in the water.
I don't usually use 4200 or 5200 on pipe joints.... although I love the stuff! Either is OK for metal if you must use it... 5200 comes readily apart on metal joints.
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Old 14-06-2015, 12:40   #6
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Re: Tips for slow seacock leaks?

You may also have a thread mismatch in your different pipe joins. 3m silicone sealant might be your best bet but for at least one of those leaks you are going to need another haul-out.
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Old 14-06-2015, 12:57   #7
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Re: Tips for slow seacock leaks?

The normal white Teflon tape is crap. Use Teflon paste or the thicker yellow or pink Teflon tapes.
If it's just the threads you can you dive and plug or seal the thru hull and fix without a haulout
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Old 14-06-2015, 15:21   #8
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Re: Tips for slow seacock leaks?

First--never install a plastic female pipe-threaded fitting over a metal male fitting.

Second--never mate tapered pipe threads to straight threads.

Third--never experiment with DIY sealants below the waterline.

Fourth--leave the Teflon tape at home. Use Leak Lock to seal pipe threads.
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Old 14-06-2015, 15:29   #9
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Re: Tips for slow seacock leaks?

In Exhibit C, the greyish glue looks to me like the color Marine Tex gets when it's set up. It's an epoxy, IIRC.

It's awfully cold in Puget Sound, but you'd probably survive diving in to put a plumber's friend over the outlet, and if you fix it with a retrieval string, you'd be able to remove it from above. Still, you've got two of them left to do. Personally, i'd feel weird about sailing with those guys leaking. I have an overactive imagination, and would be wondering how I'd tell and what I'd do when they started leaking more! That said, your boat, your risk.

There is a product called Seal Once that works pretty well on wet things.

I guess you get it that you're going to have to fix it right, and so it's really a question of timing, now.

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Old 14-06-2015, 16:13   #10
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Re: Tips for slow seacock leaks?

Leak Lock looks even better than teflon pastes such as Oatey or RectorSeal, thanks for the tip.

The only Seal Once I find is for sealing concrete, wood and masonry surfaces???

When doing thruhulls and marine plumbing, and especially while still on the hard, you can use the same test tools plumbers use. A variety of sizes of expanding or pneumatic test plugs are available at any plumbing supply house or online, and you can get air guages such as these Pressure Test Gauges by Pasco, Watts & Marsh Bellofram to dry test your work results. A pressure line should hold 50 psi on the high pressure gauge for 15 minutes. If it holds that, it should be good for 125 psi of larger water molecules. On land, drains only need to hold 5psi, but for any thruhull, I'd apply the same 50 psi standard to be safe.

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Old 15-06-2015, 08:49   #11
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Re: Tips for slow seacock leaks?

Quote:
Originally Posted by MarkSF View Post
I've found teflon paste to be more reliable than tape, either used together or the paste on its own.
I didn't know about teflon paste, good idea, thanks.

@Terra Nova, it looks like Leak Lock is a type of pipe joint compound, which is what teflon paste is. Any evidence that it works better than other pipe joint compounds, like Permatex's (product #80045)?

Interestingly the leaks all seem to have gotten better after 3 days. In the case of (A) with the teflon tape it's slowed to almost no leak (after initially about 1 drip/second upon launch). I think the teflon tape perhaps takes a bit of time to "seat" itself. Although clearly I should've put more on, and will try the paste.
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Old 15-06-2015, 10:29   #12
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Re: Tips for slow seacock leaks?

Teflon tape isn't "really" for sealing. Its for removing friction between two mating, tapered, threaded parts, so that they can be tightened to the point where they are sealed. 3 wraps.

It sounds like you aren't 100% certain your parts have matching threads. That's really not a good idea when you are talking about stuff below the waterline.

And if the male end is tapered and metal, and the female end is plastic, guess what's gonna happen when you really sock it down. (Spoiler, the female bit will crack.)

With my seacocks, there are parallel (non tapered) threads on the top of the seacock. The threads have nothing to do with the seal, well, directly anyways. When using the proper parts, the mating end of the elbow piece has a flat, machined face that mates with a corresponding flat, machined face on the top of the seacock body. These faces are where the seal is made, with a gasket or gasket-goop. The threads are there for the "nut" that attaches the elbow to the seacock and squishes the faces together.
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Old 15-06-2015, 10:31   #13
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Re: Tips for slow seacock leaks?

Quote:
Originally Posted by Terra Nova View Post
First--never install a plastic female pipe-threaded fitting over a metal male fitting.

Second--never mate tapered pipe threads to straight threads.

Third--never experiment with DIY sealants below the waterline.

Fourth--leave the Teflon tape at home. Use Leak Lock to seal pipe threads.

Excellent advice!
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Old 15-06-2015, 10:59   #14
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Re: Tips for slow seacock leaks?

For your pipe thread seals, you cannot go wrong using Permatex Form-a-Gasket #2 or #3 [NON-Hardening versions... NOT the hardening version #1]

Good for water, fuel, etc. Cheap and readily available. Gets on everything if you aren't careful...
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Old 15-06-2015, 11:00   #15
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Re: Tips for slow seacock leaks?

Quote:
Originally Posted by Terra Nova View Post
First--never install a plastic female pipe-threaded fitting over a metal male fitting.

Second--never mate tapered pipe threads to straight threads.

Third--never experiment with DIY sealants below the waterline.

Fourth--leave the Teflon tape at home. Use Leak Lock to seal pipe threads.
Fifth--double clamps on through hull fittings and any connection that could sink your boat.
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