Choosing a System

Three steps to a professional rainwater treatment system

Rainwater harvesting is a simple technology and requires hardly any maintenance.  No chemicals are needed to ensure water quality.

Step 1

Filtration: The first purification stage starts before water enters the holding tank, with the aim of keeping larger dirt particles (eg leaves) out of the tank.  The best solution is a filtration system that collects the draining water, filters it without retaining the dirt and is therefore self-cleaning.

Step 2

The holding tank not only stores the water but also purifies it in a second biological filtration step.  The tank should be able to protect the water from dirt, light and temperature.  The water in the tank must be keep calm so that heavier particles can settle to the bottom and the lighter particles float to the surface.  This is assured by the calmed inlet.  Thanks to the floating extraction, the cleanest water is always taken approximately 15cm below the water’s surface.  The holding tank must be specially dimensioned so that the stored rainwater overflows several times a year, thus the floating dirt layer is disposed via the overflow siphon.

Step 3

A pump is needed to supply the rainwater to the application.  The pump should be silent running and corrosion resistant.  The installation of a mains water back-up system is required to ensure permanent readiness for service of the rainwater harvesting system.  This component provides the supply of mains water into the system in the event of rainwater shortage.  For easy installation and maximum operation safety, our Conderflo Manager can take over the function of pump and supply unit in a single product.  The pipe installation should be corrosion resistant as well.  The pipe installation and water taps must be marked clearly (according to WRAS).  The water taps should be detachable but secure.

Enjoy soft, natural water

  • Ideal medium for enabling plants to absorb minerals
  • Better washing efficiency – 50% of detergent can be saved
  • Due to the softness of the water, there is no limescale build up in the washing machine and no urinal calculus in the WC

Water quality

If a rainwater harvesting system is professionally designed and installed there is no reason for any doubts about domestic use of rainwater regarding hygiene aspects.  This has been verified by several scientific reports and researches, eg in a long-term study by the State Hygiene Institute in Bremen, Germany.  One result was that there is no difference between the quality of clothes washed with potable water or rainwater.

System sizing

Rainfall can be sporadic but the tank size is usually less than imagined.  As a guideline, size the tank of the system to hold 18 days worth of demand or 5% of annual yield, whichever is lower.  To calculate the optimum tank size, first calculate the potential yield.  Once you know the potential yield, simply find 5% of this.

Roof area in m2 x drainage factor x filter efficiency x annual rainfall in mm x 0.05.