Reduced shower flow is usually due to limescale buildup. This can easily be removed with a descaling product Tools and materials Screwdriver, bowl, descaling solution

Unscrew the shower head from the hose. Unscrew the spray plate and immerse it in descaling solution. Leave it in the solution for specified length of time. Flush any remaining scale from the pipes before replacing the shower head.

Extracted from DIY- Know How With Show How published by Dorling Kindersley, price £25.00. Copyright © 2006 Dorling Kindersley Ltd, Text copyright © 2006 Julian Cassell and Peter Parham