Domestic rainwater harvesting systems can help save on laundry detergents

The installation of domestic rainwater harvesting systems leads to substantial savings for families on detergents and other additives used for laundry purposes, says a study by Spain based Institute of Environmental Science and Technology.

The study arises from the current need to find corrective and preventive measures to deal with water supply problems, particularly in view of the effects of climate change. It shows that 80% of the savings incurred by installing these systems come from reduced consumption of detergents and fabric softeners. This is because rainwater is soft water, meaning that it needs 59% fewer additives for washing than hard tap water.

The findings show that when rainwater is used to wash clothes there is a considerable saving on detergent. As soap does not completely dissolve in hard water, some of the present minerals will remain in the materials or cloths after being washed. This means more water is wasted in trying to wash off the soap, and also more rubbing and scrubbing.

On the other hand, rainwater contains trace amounts of certain ions like sodium and potassium that help dissolve soap and lift sediments like soil and excess soap from previous washes from your clothes. When clothes are soaked in rainwater overnight, the washing process is greatly reduced as rainwater should already loosen dirt and other sediments, thereby greatly extending the fabric’s life span.

The doctoral thesis concludes that, for laundry purposes, rainwater collected in tanks is an improvement on tap water, especially in areas where tap water is extremely hard or scarce.