Rainwater for Laundry

Using Rainwater for Laundry

Every person in Canada uses 329 litres of drinking water per day on average. Approximately 25% or 82 litres is used for laundry. A four person household uses 4 x 29930l/year = 119720l/year for laundry.

e-Canada_domestic_water_useThere is no question that using rainwater for garden irrigation and flushing the toilet is an excellent way to save precious drinking water. Opinions differ though when it comes to using rainwater for laundry, primarily because of hygienic concerns.




Rainwater is lime free

From a technical point of view rainwater is much better for washing laundry than most drinking water. Rainwater does not contain lime and does not inhibit the effectiveness of the active substances in the detergent. Depending on the lime content of the drinking water up to 60% of laundry detergent can be saved. Using a water softener is unnecessary and lime build-up on the heating elements of the washing machine does not occur, thereby saving energy and prolonging the service life of the machine.

Rainwater quality: Better than you think

Concerns with rainwater used in washing machines are usually not founded, since the quality of the rainwater in the cistern is usually of excellent quality.  The quality of water from a professionally installed rainwater system equals that of bath water. This requires that the rainwater is stored in a cool and dark tank. Otherwise germs and algae could grow and compromise the quality of the rainwater. An underground cistern meets these criteria.


Usually a rainwater system consists of two cleaning stages. Big particles like leaves are caught by a filter with holes between 0.2 and 0.8 mm. The filter should be cleaned by hand at least once a year. The second cleaning stage is a self-cleaning stage. By allowing the rainwater to sit in the in the cistern for a long time, particles clump together and sink to the bottom of the cistern. It is shown that during this process germs cling to the particles, thus improving the quality of the rainwater. Approximately 1mm of sediment accumulates at the bottom of the cistern per year. This sediment should be removed every ten years or so. One should refrain from any other cleaning measures of the cistern, to ensure the quality of the collected rainwater. A film will form on the inside of the cistern, improving the self-cleaning properties of the system.