GRP pipe wall consists of three layers perfectly adherent to each other and having different characteristics and properties in relation to their function.

		Inner Liner
		Structural Wall
		External Liner

	Material	GRP/GRV	GRE
Inner liner	Veil (Glass)	10%	10%
	Resin	90%	90%
	CSM (Glass)	30%	-
	Resin	70%	-
Structure
	Roving (Glass)	70%	70%
	Resin	30%	30%
External liner
	Veil (Glass)	10%	10%
	Resin	90%	90%

Inner Liner:
Liner or chemically resistant layer is the internal layer of the pipe. It is in direct contact with the conveyed fluid. This layer has the function to guarantee the resistance to the chemical corrosion and the impermeability to the pipe. Liner has the internal surface, namely be one in contact with the conveyed fluid, particularly smooth. This characteristic of smoothness reduces the fluid head losses to the minimum and opposes the growth of mineral deposits and algae. The liner is made of two monolithic sub layers. The inner one, in direct contact with the fluid, is reinforced with glass veil, with a resin content of 90% and the outer one is reinforced with CSM glass, with a resin content of 70% by weight. The standard liner thickness, is about 0.5 to 1.5 mm, higher thickness can be produced on request.

Structural Wall :
Glass reinforced layers guarantee the mechanical resistance of the whole pipe against stresses due to internal and external pressure, external loads and thermal loads. For GRP/GRV pipes, this layer is obtained by applying on the previous partly cured liner, continuous roving of glass wetted with resin, under controlled tension. For GRE pipes, the structural wall is wound directly on a wet liner. This layer can contain aggregates like silica sand. Thickness of the mechanical layer depends on the design condition. .

External Liner:
Top coat or external liner is the outer layer of the pipe which consists of pure resin added with UV protectors to protect the pipe from sun exposure. In case of severe exposure condition like aggressive soils or very corrosive environment, the external liner can be reinforced with a surfacing veil or added with fillers or pigments