BS 4994 (formally: British Standard 4994:1987) is the "specification for the design and construction of vessels and storage tanks in reinforced plastics".
Dual laminate construction, simple FRP with glass mats, or a combination of unidirectional filament winding are common.
DUAL LAMINATE : A thermoplastic lining material, preferably 3mm to 5mm thick sheet functions as a corrosion barrier.
FRP which is constructed over this lining provides the strength requirements for materials to withstand design conditions like pressure, vacuum, hydrostatic load, etc.
PP, PVC, PTFE, ECTFE, CPVC, PVDF are used as common thermoplastic liners.