Rainwater Collection – Quality Issues

This is a fairly typical rainwater collection installation.

Gutters discharging to a pipe which discharges onto a screen fitted to the tank access point, cheap and cheerful!

I must have seen it hundreds of times . . . . . . but it has some negative implications on the water quality you will get from the tank!


  1. Although the screen keeps leaves, mozzies, and other debris out of the tank it lets sunlight in. This will encourage algae growth inside the tank.
  2. At the top of the tank the screen is out of view and consequently hardly ever gets cleaned. As a consequence the leaves rot and organic materials gets washed into the tank providing nutrients for that algae.
  3. Discharging water into the top of the tank isn’t the best location (see this link:  Inlet Improvements).


  • Install a cover over the access point (Something like a round dustbin lid with a hole for the inlet pipe) This will keep the light out, but the issue of the rotting leaves will remain.
  • Screen the leaves out at the gutter discharge using a rainwater diverter with a self cleaning screen (for an example see this link: Supadiverta), and pipe the inlet  flow to the bottom of the tank.


For more posts see Rainwater