Here’s a short video I made about drain worms in my shower because I realised that there was very little about them on the web. Hope it helps you beat these little nasties.

http://www.youtube.com/watch?v=px_f0JbwIrU&list=UU4bKk4PGekB_Wzqg5I1v8QA&index=1&feature=plcp

In short, the Drain Worms hatch from the eggs laid by the Drain Fly in a layer of scum just above the water level in the pipe. So the worms you kill today will just be replaced by more hatchlings in the following days. The worms grow up to be Drain Flies and then they lay more eggs.

You've got three choices to break the life cycle: 1. Kill the flies, 2. Block the flies from reaching the scum by keeping the drain plugged or covered when not in use, 3. Open the grate so you can thoroughly clean the scum away.

Although you see them in the shower tray grout, they actually start their journey from the drain - so stop them before they leave the drain.

Check out the video for a closer look.
Cheers
Rusty