Drinking water supply in periods of low precipitation


If a cistern is designed to generate rainwater as industrial water, the question arises in dry and rainy periods how to ensure a replacement supply. While garden irrigation is sufficient for a water source independent of the cistern, the water supply of connected equipment can be provided by drinking water supply.

Device supply and connection options

In most cases, a cistern seldom supplies enough rainwater to store the garden irrigation and to supply, for example, toilet flush and washing machine throughout the year. For garden irrigation, an external water connection is sufficient for used cistern water, just like a tap connected to the regular drinking water supply.

In piped installations with directly connected water consumers there is a risk of "dry running" of the equipment or flushing. An automated drinking water supply can fill up the used rainwater in the cistern. Connection options are possible directly in the tank container or on the pump line.

In the tank container or on the pump line

Anyone who builds a cistern himself has the option of installing a float switch in the cistern container. On the one hand, he can control the level indicator from which the water level can be read or, on the other hand, automatically activate a magnetic switch after reaching a defined minimum. He opens the drinking water supply, which replenishes the tank container.

A more complex and more precise in water consumption construction is the connection of the drinking water supply to the pump line. In this variant too, a float switch measures the water level in the cistern and triggers a magnetic switch when the load is low or empty. The drinking water supply takes place in a separate buffer tank installed directly on the pump line. From here, the pump "draws" exactly the amount of drinking water that is needed for toilet flushing or washing machine.

Official operating conditions

Decisive legislation when approving a cistern is the guaranteed separation of the rainwater and drinking water circuits. For this purpose, the following structural requirements are mandatory in order to obtain an operating permit:

  • The drinking water supply must be able to drain freely and must always be above the maximum possible filling level of the cistern.
  • The minimum distance to the rainwater surface must be twenty millimeters and, if necessary, twice the supply diameter.
  • Backflow and back suction effects may not be possible.
  • The installations and pipes of the water circuits must be complete and separated at each point.
  • All pipes and outlets carrying rainwater must be labeled as such to avoid confusion with potable water.
  • Even temporary connections of the water circuits, for example with a hose are not allowed.
  • The competent authorities, usually lower water authority and / or health department are authorized in cases of doubt during inspections to immediately prohibit the cistern use.

Tips & Tricks

If you have not had to use your potable water supply for a long time, rinse the pipes, taps and other components at least once a year to prevent damage, increased porosity of seals or bacteria formation.


Video Board: Understanding the SEQ Water Grid