Material: Made from durable, UV-stable, injection-moulded plastic (uPVC).

Design: They come in various shapes (oval, rectangular, round, sometimes conical or boomerang-shaped) and often have small prongs or clips on the back that push-fit into the weep holes.

Size: Designed to fit standard size drainage slots or round drilled holes (e.g., 5-6mm round holes or slots around 40mm wide x 12mm high).

Colors: Available in common uPVC colors like white, black, brown, grey, and sometimes “oak” or “mahogany” to match window and door profiles.

The drainage cap’s role is to:

1. Prevent Backflow: Stop wind-driven rain from blowing back into the drainage channels, which could lead to water ingress into your home.

2. Keep Debris Out: Prevent dust, dirt, leaves, and other external debris from entering and clogging the drainage channels. Blocked channels can cause water to build up inside the frame and potentially leak indoors.

3. Deter Insects: Reduce the chances of insects nesting inside the window or door frames.

4. Maintain Aesthetics: Cover the functional weep holes, providing a neat and finished appearance to the exterior of the window or door.

5. Thermal Efficiency (Minor): While not its primary role, a missing or damaged drainage cap can slightly reduce the thermal efficiency of the window by allowing more uncontrolled air movement.