How to test a through hull for leakage.

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brianbob

I recently purchased a Hunter 20 for trailer sailing. While getting it ready I found that the drain hose from the sink to the through hull fitting needs to be replaced. Before I simply replace the hose, I would like to check the through hull valve to make sure it is safe. Can someone tell me the best way to do this? Thanks, Brian
 
Sep 25, 2008
7,511
Alden 50 Sarasota, Florida
don't think there is one

Brian About the only way to be sure it is "safe" (I assume you mean if it leaks) is to put the boat in the water and see. I'm sure this is obvious already but can't think of any other way. If you are worried about it, why not simply replace it? If it is a gate valve, replace it regardless as it will eventually fail even in fresh water.
 
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Benny

There is a couple of things you can do,

Give it a visual inspection on the outside and on the inside; make sure there is no corrosion making the part ready to desintegrate in the next couple of days. On the inside give the valve and the through the hull a good jerk back and forth. If you find it is loose I would install a new one. The other part that can fail is the valve. Work it back and forth, close and open a few times applying pressure at the handle in both directions. Make it withstands some abuse. Replace the hose, lock the valve, fill the sink with water and check for major leaks. If there are any leaks leading to the interior of the boat with that small pressure replace the valve. If your through the hull and valve pass these simple tests chances are very good it will not fail tomorrow. I consider a safe through the hull one that will not lead to a catastrophical failure. A leak in a valve does not necessarily make it unsafe. Taking into consideration that you are talking about a trailer sailer and that you will be pulling that boat out of the water frequently if not everytime you use it. I would not advice the replacement of the the through the hull or valve at this time until you further test it under sailing conditions. If it were a heavy keel boat I would certainly would recommend a more rigurous inspection but you should be fine. For more piece of mind carry a set of wood plugs and a mallot. Nice looking sailer.
 
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brianbob

thanks

Thanks for the responce. I will check for leaks and then go sailing. I do plan on having plugs on board just in case. Just seems like a prudent thing to do.
 
Sep 25, 2008
7,511
Alden 50 Sarasota, Florida
physical abuse

probably isn't a wise test particularly if it is not a true seacock properly fixed to the hull. At best, it can create problems not previously existing and at worst can rip a thruhull out of the glass not adequately bolted to it or loosen it to the point of probable failure. You didn't say what type valve it is or why you suspect it but the prudent thing to do would be replace it if in doubt.
 
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brianbob

The boat is old

It has been restored to a great extent. The through hull I assume is original to the boat. It is used for sink waste water to exit the boat. The valve looks mildly corroded on the outside. It has a round handle to open and close it. The handle only turns a quarter turn before it stops. I agree that physical abuse does not make sence. I intend to try to look inside the valve with a flashlight to see if I can see if their is any damage inside. Then replace the hose (which was broken on one end) and fill the sink to check for leaks. I really don't have any intention of using the sink but just want to make sure the treough hull does not lead to catastrophic failure.
 
Sep 25, 2008
7,511
Alden 50 Sarasota, Florida
Round handle = gate valve

Brian Gate valves (similar to your home exterior water spigot handle) are not only useless but dangerous on a boat. They were common on older boats but you never see them on newer ones for good reason. Do yourself a favor not to mention the peace of mind it will bring to simply replace it with a proper seacock and stainless ball valve (the type with a handle). If you never intend to use ot in the future, remove it and glass in the hole. Whatever you decide, get rid of it!
 
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brianbob

Thank you

for your responce. This was what I was looking for. I have been looking for replacement parts just in case. Thanks again
 
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Benny

Yes you have a gate valve and it seems to

be stuck. Take it apart and see in what condition the innards are. Hunter used gate valves in boats of that era and there are still many boats out there that have them. I have experienced a failure on a gate valve in a keel boat as I was closing it and ended up with the handle in my hand and as I pulled it the gate came out and water in. It was as if the neck of this 1 1/4 inch valve desintegrated because of corrosion. I placed the gate back and placed a plastic bag inside and held it with duck tape. I remember because I was readying this boat for a hurricane that had been forecasted for that night. It held fine for another month before the boat could be taken for a haulout. Like I previously said I would not be so concerned for a boat that sits on a trailer. If you want to replace it that is the best course of action but since you were asking I figured you were weighing your options. What I meant by jerking the valve and abusing it a little was that if it was going to fail it would be better that it fail on the hard than before you put the boat in the water. Gate valves have gotten a bad name because most of the in usage are old and those which fail are badly corroded but the dangers associated with the design itself are overplayed. I would be more concerned with the integrity of the through the hull than with the valve itself.
 
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brianbob

after taking the valve apart

I was able to free up the handle and open it completely. It looked good on the inside and seated nicely. I think I will first replace the hose. I can see the value of a valve handle which can be checked visually to make sure it is closed. I also intend to replace the valve, however I think the boat would be safe for daysailing and weekending as it is. Thanks for your responces. This is my first production boat and I have a lot to learn about the fittings and such.
 
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