Can Rainwater Be Used for Household Appliances with a Cistern?

Cistern Sizing for Household Appliances

When sizing a cistern for household appliances that use rainwater, consider the total water demand of the household. A general rule of thumb is to estimate 12-15 gallons of water per person per day for non-potable uses such as washing machines, toilets, and irrigation. For a family of four, this translates to 48-60 gallons per day. A cistern with a minimum storage capacity of 1,000 gallons is recommended to account for fluctuations in rainfall and household water demands.

Treating Rainwater for Household Use

Before using rainwater for household appliances, it must undergo treatment to remove contaminants and particles. A simple treatment system consists of a first flush device to divert the initial flow of rainwater from the roof, a sedimentation tank for particle removal, and a disinfection system such as a UV filter or chlorinator. Regular testing of the rainwater quality is essential to ensure it meets the required standards for household use.

Connecting Rainwater to Household Appliances

Connecting a cistern to household appliances requires a proper piping system to prevent contamination and ensure safe water usage. Piping materials should be food-grade and resistant to corrosion, such as PVC or PEX. The system should also include backflow preventers to prevent contaminated water from entering the potable water supply. A pressure tank and pump may be necessary to maintain a consistent water pressure for appliances such as washing machines and dishwashers.