The roof panels (Layer: ROOF-PNL) are typically thinner than the wall panels (4mm vs 6mm). Why? No water pressure.

But look for the ventilation block (Layer: VENT). GRP tanks are sealed. Without a vent (200mm x 200mm with insect mesh), the roof will implode when a pump draws water out, or explode during thermal expansion.

Before opening AutoCAD, you must understand the anatomy of a GRP tank. Unlike welded steel tanks, GRP tanks are modular.

Key components found in every GRP drawing:

Although this article focuses on AutoCAD, the industry is shifting. If you are generating GRP drawings, consider the "Information Delivery."

Actionable Tip: When saving your GRP drawing, use _WC (Write Block) to extract the base unit. This creates a reusable library of GRP modules.