Fiberglass cloth is used in potable water tanks, but should be laminated and coated with a resin that is formulated entirely with substances that comply with US FDA Regulations 21 CFR 171.105 and 21 CFR 171.300 for adhesives and coatings that may be used safely as components of articles intended for use in packaging, transporting, or holding food. MAS makes a Potable Water Epoxy Resin that can be used for fiberglass water tanks.