Water leak on top of MKI water tanks

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blobaugh
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Joined: 4/1/21
Posts: 26
Water leak on top of MKI water tanks

I flushed Shadow's water tanks last weekend, then refilled from the starboard inlet. A buddy called on Facetime to get a tour of the boat and I left the water running, overfilled the tank till water came out the vent. Whoops. I had the covers off the aft cabin so I could look at both tanks, and they were leaking.... from the top!

I am not sure if this is stock or not, the tank vents are Teed together. So when the starboard tank filled up and water went up the vent line, the centerline tank was filled via the vent. That seems less than desirable. 

Anyhow, I know that put a good amount of pressure inside the tanks themselves, but that leaking bothers me. I know there will be more times in the future when someone fills the tank and does not pay attention.

Is this a common occurance?
What are the thoughts on stopping the leakage?
Am I correct in assuming any water leaking around the tanks will go straight into the bilge?
What about that vent line T? Is that standard? Any reason not to seperate that into two vent lines?

I have attached some photos so you can see the leakage.

Ben Lobaugh
s/v Shadow
1987 MKI #724
Tacoma, WA
Cruising and Racing

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dlincoln3
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Joined: 4/24/16
Posts: 144

Mine do the same.  The large threaded plug on top does not seal.  In fact, it doesn't ever bottom out or seat at all, and if you keep screwing it in, it will fall all the way into the tank.  I don't know why it is designed this way, but I don't think it's a huge deal either way.

Don Lincoln
"Nancy Lynn"
1993 Catalina MK1.5, Hull 1238
LaSalle, MI (Lake Erie)
Universal M-35AC

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EUREKA
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Joined: 1/20/09
Posts: 115

I also had the same problem in my 1991 C36. I used all kind of sealants but no one work. Tired of finding water in the bilge each time a filled the tanks (I had an extra tank under the V berth) I ended by changing all 3 tanks with a local small business that are only dedicated to built "a la carte" any kind of tanks.

No more problems!

Eladio Vallina

C-36 TR EUREKA II
Hull 1122 (1991)
Home port Barcelona (Spain).

blobaugh
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Joined: 4/1/21
Posts: 26

Your comments make me feel a bit better. I can deal with a little leakage for now. New tanks will go on the projects list, on the way bottom of the list :). 

Ben Lobaugh
s/v Shadow
1987 MKI #724
Tacoma, WA
Cruising and Racing

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Chachere
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Joined: 10/27/10
Posts: 825

We've done that as well.  Some telflon tape on the top plug (inspection port) of the tanks seems to help.  But the tanks are apparently not designed to be over-pressured that way.   No a big deal, the excess just drains to the bilge (at least from the center tank).

Matthew Chachère
s/v ¡Que Chévere!
(Formerly 1985 C36 MKI #466 tall rig fin keel M25)
2006 Catalina Morgan 440 #30.
Homeported in eastern Long Island, NY

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