[JLRedfish]

I own a 1986 Tiara 2700 Open with twin Crusader 270 inboards.  The 30 gal. aluminum fresh water tank would leak down in about 3 hours.  I keep the boat on a trailer at my shop.  The tank is located under the 2 90 gal. fuel tanks.  I didn’t want to drain and pull both tanks to be able to remove the water tank.  I did have access to the back end of the fresh water tank with the fill, vent and discharge ports. I used an endoscope to try to locate the leak, but could only determine that it was in the forward section of the bottom of the tank.  I flushed the tank and completely dried it with rags and compressed air.  I dropped the trailer tongue to the ground which gave a forward tilt to the tank.  I inserted a 3/4” hose thru the fill port and along the inside past the baffles to the front of the tank.  I poured about 8 oz of liquid Flex Seal down the hose.  After the hose emptied, I jacked up the starboard side for about 10 minutes, then the port side for about 10 minutes.  After that I removed the jacks and let it remain flat.
I let it sit for a day and a half then filled it with water.  No leak.  Since this tank is not used for potable water, the Flex Seal should present no problem.  I’ll see how it holds up this year and will update if it starts leaking again.  Thought this might come in handy if anyone had a similar problem.