The floating removal provides clean rainwater

The floating removal of rainwater from the cistern uses a simple physical principle. The smallest particles of dirt move in the collected water as suspended particles down. Therefore, with calmed cistern contents, the water can always be skimmed off at the top in the cleanest state.

Suspended particles sink

All coarse dirt particles are prevented from entering the cistern by mechanically acting cistern filters. By basket, filter or cartridge filter also sand and sludge can be retained to some extent in the passing rainwater. Depending on the pore size of the filter cartridges, small particles remain in the water.

When the rainwater "comes to rest", the suspended particles begin to settle down because they are heavier than the water molecules. This creates a permanent sediment layer on the bottom of the cistern. The "clearly drizzled" cistern water is now cleanest on the surface.

Float ball, suction hose and pump

The clean water is sucked in from above by means of a pump and discharged for use as service water. For this floating withdrawal a float ball, a suction hose and a pump are required. The suction hose delivers the rainwater in a quality of cleaning that is suitable for connection to a domestic waterworks.

On the water-filled float ball, the suction hose is attached, which leads to the overflow or overflow of the cistern. The weight of the ball keeps the end of the hose permanently under the surface of the water and drops parallel to the falling water level. The length of the tubing determines the end of aspiration because if the water level is too low, the ball connected to the tubing begins to "float". The end of the hose exits the water and draws air.

It is important to choose a pump that has an automatic dry-run switch to prevent damage to the motor. Suction pumps can be used as pump types up to a maximum delivery height of eight meters; in addition, submersible pumps must be used.

Length of the suction hose

The ideal length of the suction hose should be determined by several factors:

  • The more restless the cistern water, the shorter the hose.
  • End suction at the latest at double the level of the sedimented layer.
  • The lateral edges of the cistern may not be reached from the end of the hose.
  • If the depth of the cisterns is large, the float ball should be "guided" with the end of the hose to allow a long length without lateral impact.

At the end of the hose, a further filter element is normally attached in order to bring about an additional filter effect. The float ball can bind self-influx particles during prolonged retirement, which are avoided by occasional "stirring" of the cistern water or a maintenance pump.

Tips & Tricks

Decisive for the removal of water with the least possible amount of suspended particles is the settling time in calm water. Therefore, you should stop the floating withdrawal when new rainwater runs after. Ideal is the withdrawal after rest periods of about 24 hours.

Video Board: Rain water Harvesting and Collection for Drinking purpose