NO potable water tanks made from bare FIBERGLASS !!!!! - unsafe and unhealthy.
Would strongly advise against the use of a FRG tank for potable water. Styrene resins are definitely contraindicated because of the continued leachables of the non cured styrene (monomer). Standard Epoxy continually leaches amines and other fragments. Styrene polymers are prohibited by NSF/FDA regs. for potable water; so is 'standard' structural epoxy !!!
For ultrapurity and a tank fully to FDA/EPA standards consider POLYETHYLENE. BUT a 44 gallon rotomolded poly tank will not have baffles which are important for hydraulic impact /life considerations ... Plus, you dont want 300 lb. of water 'shifting about' in a heavy sea state causing additional boat handling problems ---- because you simply cant put proper baffles in a large rotomolded poly tank!!!
Several solutions:
1. Several small manifolded rotomolded poly tanks
2. Custom made FRG tank with
polyethylene faced internal liner panels and the panel seams all welded with polyethylene. Such poly faced FRG panels are hard to get, the 'welding' of the seams requires great expertise and special plastic welding equipment. Specialty FRG tank builders using poly faced panels are uncommon ... unless you live in an area with lots of chemical process or biopharm industry. Not a DIY job.
3. Rebuild the old aluminum tank as necessary (in place) with structural epoxy + cloth where needed .... then covered with an FDA/NSF approved low-amine,
potable water rated, 'lining' epoxy. Just roll-on ALL internals until you have ~250 mil thickness. Might require that you cut in large access ports on the top of the tank to allow 'work room'. Closure can be 'studs' screwed and epoxied along the underside of the cut margins .... then you only need to fabricate new flange closures from new plate, etc. All would bolt together using BUNA strip rubber as the 'gasket', etc. Ive rebuilt 100+ gallon baffled water tanks in this build-a-tank-inside-a-tank manner, you just use the internals of the old tank as the 'mold' for the thin-walled new tank; cost is about $75 for NSF materials, $20 for the structural epoxy and $20 for the 'studs', etc.
Benefit with a low-amine epoxy 'liner' - you can now properly shock sanitize the tank with clorox/chlorine and can low maintenance dose (2-4oz Clorox / 100 gal) to keep the 'growth' under control. Maintenance dosages of 0.5-1ppm (common municipal dosage) chlorine would eventually destroy a bare aluminum tank. Free chlorine attacks the aluminum and forms aluminum chloride ... all that 'white stuff' that you will find in the bottom when you open the old tank.
http://www.nsp-specialty.com/pdf/120nsftds-07.pdf
hope this helps.
