Fresh Water Tank Leak

[ronmar]

I have a 1993 350 Aft Cabin. My fresh water tank is under the bed in the aft cabin and is leaking. Upon inspection the leak appears to be a crack in the plastic tube where it screws into the tank. (tube exits tank straight out bottom end and threads into an elbow that connects to main water lines) I was unable to remove to see what size as did not have the right tools with me at the time. Will be going down again next weekend and hoping to take the parts with me as my marina has no parts and in a small town where parts are hard to find. Does anyone know what size the tube is? Also when replacing should I use Teflon tape?

[mjk1040]

I can only guess but would bet on 1/2". And yes I would use Teflon tape on the fittings.

[bud37]

When you get it apart, have a close look to make sure it is the fitting that is cracked and not the tank at the threads.
Regarding the teflon tape,I would not use it here, just a paste type thread sealant for the plastic fitting you are using....the reason being , if you were to put too much tape and then overtightened you will stand a very good chance of splitting the tank threaded fitting...FYI you can even split brass fittings this way.Good luck with it , be careful and all will be fine.........

[km1125]

I'm actually in the "use the tape" camp, but you certainly do have to be careful for what Bud37 says about applying too much wrench on those plastic fittings.

I'm confused about this part "tube exits tank straight out bottom end and threads into an elbow that connects to main water lines"

Use your phone to take pictures of everything you're working on. Gives you some good "before" and "after" pictures for down the road, but very helpful when you're in the middle of a project and not near the boat. Years ago I bought a cheap digital camera and left it on the boat, and had several SD cards to shuttle back and forth to hold the pics while I was working on projects. Now I just use the phone.

[ronmar]

Source of the post I can only guess but would bet on 1/2". And yes I would use Teflon tape on the fittings.

Thanks, going back Friday to tackle. Appreciate the help

[ronmar]

Source of the post When you get it apart, have a close look to make sure it is the fitting that is cracked and not the tank at the threads.
Regarding the teflon tape,I would not use it here, just a paste type thread sealant for the plastic fitting you are using....the reason being , if you were to put too much tape and then overtightened you will stand a very good chance of splitting the tank threaded fitting...FYI you can even split brass fittings this way.Good luck with it , be careful and all will be fine.........

Thanks for the tips> Always appreciate plumbing help!

[tomschauer]

For some reason, many of these boats use 5/8 ID hose, but 1/2 NPT threads.
Contrary to most of the above, I personally use a bit of 100% silicone on the threaded fittings, and make sure to let it cure for a few hours before adding water. This way there is no danger of cracking the tank due to too much tape, and the silicone will seal better than pipe dope (thread sealant).

[ronmar]

Source of the post For some reason, many of these boats use 5/8 ID hose, but 1/2 NPT threads.
Contrary to most of the above, I personally use a bit of 100% silicone on the threaded fittings, and make sure to let it cure for a few hours before adding water. This way there is no danger of cracking the tank due to too much tape, and the silicone will seal better than pipe dope (thread sealant).

Thanks!

[ronmar]

Well actually my problem much bigger than fitting issue. Found tank actually leaking from the bottom. After removing entire tank, discovered significant corrosion issues. A hole about size of pencil diameter near the center, and lots of pink spots on the bottom. Took it to be welded and discovered those pink spots were more corrosion, pitting, and holes. Now weighing having new bottom welded on or finding another tank.

[Midnightsun]

Nothing worse than aluminum tanks in older boats. One thing that never should have been if you ask me yet they were used in holding tanks and water tanks and all need to be replaced eventually. I strongly suggest you replace it with a polyethylene tank which is now the norm. These will never corrode and will last forever. They have even gone to this in the automotive industry for gas tanks (maybe a plastic derivative) and are starting to show up in boats now, by far a much superior product yet I assume the price is close to the same or cheaper.