Aluminum water tank leak

[tkeithlu]

Pheiffer, I'm going to change my recommendation after further thought and the added information from you.

Consider constructing an entire patch out of think aluminum plate, complete with threads for the outlet. Drill anchoring holes around the edges of the patch. Cut a gasket for it. Cut out the old outlet, and mount the replacement with sheet metal screws. In effect, replace the entire problem area rather than repairing it. The result would be stronger, and work without questions as to its strength.

[fourlyons]

I talked with the technical department of West Systems, 9 years ago now, and they didn't like the idea of using epoxy in a potable water application. If I remember it was a concern about unmixed amines from the hardener.

Maybe that was from an over abundance of caution, but something to consider.

[DeValency]

It all depends on the size and location of the leak.

In many cases, it is close to impossible to locate a micro leak. I have one at a high level of one of my SS water tanks. It is 375 liters in capacity, well located under the saloon settee and the internal dividers make it impossible to reach all the seams. I have seen this material, for spraying inside with a long garden sprayer flexible tube and nozzle:
http://microleak.com/

Anyone with experience with this material?

Have also purchased, after a very long consultation process with 3M a two component material called Scotchkote. - it is basically a liquid brushing epoxy, appropriate for drinking water tanks, although we don’t use the boat tanks water for drinking. - yet need to try this out

Bladder; heard about it a lot. Might be ok for small, undivided tanks, where there is an easy way to connect to the draining (close to bottom) and filling on top, but I don’t see how it would work with any of my SS tanks (all are 375-400 liters each on both water and diesel). Removing the tanks will be extremely difficult - although possible without destroying half of the interior cabinetry (or worse [emoji33]) as seen in other boats.

On a SS diesel tank, I had, years ago, a positive success when a crack in a seam, could be fixed with JB Weld 2110 Metal Fuel Tank Repair Kit (epoxy) with added JB Weld 8281 on top of the first coat - where I could actually reach the leak from both inside and outside after tedious efforts. - as hard as it was, in comparison to removal and repair/welding etc., it was by far a way more practical solution.

[Dougtiff]

SPLASH ZONE, sticks to anything.

[Djarraluda]

Several posts here refer to attaching a repair plate with screws. As you are deadline with an aluminium tank, be careful! Stainless screws into aluminium and water will cause corrosion and I doubt the ability of Duralac or Tefgel of similar to be appropriate at low level in in a fresh water tank.
Check the data for toxicity and long term use under water, or if the base tank metal is thick enough, drill and tap so you don’t penetrate the wall. Blind rivets (closed end) May be a better mechanical fastening!
Roger

[Pfeiffer]

Great information and thanks to all of you. I just bought this boat and after closer inspection, it appears that the leak is from a corner seam just above the valve and not at the valve itself I have an an access opening that I can reach through and feel that at that seam someone has tried to fix it before. It feels like there is a soft sealant, possibly silicone. My plan is to scrape that out, clean and sand as much as possible and then epoxy from the inside. Sound reasonable? Removing tank is a major, major problem, and it does not lend itself to insert a bladder because my only access is a 6 inch opening at one end of a 75 gal tank.

[keepondancin]

I have used gray Marine-tex on a small seam leak. Got about 7 years out of it. Have to do it again, and I am going to use JB Weld, because I have open tubes of it. Use the usual procedure of cleaning and degreasing, then patch.