The fresh water tank in my boat is molded in place fiberglass with a baffle. The top of the tank is fiberglass covered plywood with a gasket and inspection port. It is removable.

The top of the tank is delaminating. (the tank itself is not leaking and appears sound... although I will better verify this, after removing the top)

I was just thinking to replace the top of the tank with a clear piece of Plexiglas. There is a local supplier in the area, and I can easily get the stuff in just about any thickness or sheet size. I would of course go ahead and put in an inspection port or two to allow cleaning of the tank.

I figure this stuff is nearly indestructible, and would allow me to visually see how much water I have at any time. (there are no tank gauges)

The tank itself is located under the quarter berth, so the top would never see the light of day.

I am trying to figure out what the downsides of this idea might be. I really cannot think of any. Cost might be one... this obviously will cost more than just glassing over another sheet of marine ply. But I don't believe the cost is that great, over all. Gasket inspection and tank inspection will be the upsides.

A 3/8 thick sheet of Plexiglass 48" X 48" is $202.46. A 3/4 in sheet (4'x8') of marine ply is about $70. Epoxy, mat, hardener, and gel coat might be another $40.

So for the Plexi, I am looking over double the cost, realistically. But being able to see the whole water tank at any time... "priceless."