Rainwater can save on wasted resource

WITH THE arrival of the rainy season, you can avoid flushing expensively processed water down the lavatory and save money on water bills at the same time.

Rainwater can be used for the flush and that will save fully 25 per cent of the daily household usage of drinking water from going straight into the drains. That also represents a quarter of your water bill.

The traditional lavatory flush is a crazy waste of processed water and every homeowner should consider if a rainwater-fed system is practical for their property.

It is a very simple concept: a water butt filled directly, or via a rainwater diverter, from the guttering downpipe. The water butt should be sited above the level of the lavatory cistern and is then connected by pipe to the cistern.

The bigger the water butt, the better, as it means you will have more “flushing capacity” to get you through dry periods.

However, it is best to leave the mains water supply connected to your lavatory just in case, and you can simply turn this off when not required – there is usually a small tap on the cistern.

The water butt must be above the height of the cistern in order for gravity to fill it, so that means it is only really practical for a lavatory on the ground floor.

A minimum height of 50cm above the the cistern will do, but more height equals better flow. You may need to build a simple structure on which the barrel can sit.

The top of the barrel must have an overflow drain connected back into the gutter system, so it will not overflow and cause water damage. There should also be an outlet – ideally with a tap – at the bottom of the barrel.

Two filters should be fitted: one at the top (on the down pipe, or across the entry to the barrel) so that debris and flies cannot get into the barrel; a second filter should be fitted somewhere in the pipe or the connection to the cistern.

This is most easily achieved by using a rubber washer that already has a filter, such as those you see on flexible shower pipes.

You also need to insulate the pipe that goes into the house from the water barrel to protect it against freezing.

Connecting the rainwater feed pipe to your cistern is a simple matter, as most already have water connections on both the right and left hand sides so you
probably have a spare already.

Voilà – one rainwater-fed lavatory-flushing system and lower water bills.

This column is written by Marc Asker, head of EcoPower, a renewable energies company that he set up in 2007. He has been in the industry since 2003