In general, industrial water should not be used as drinking water unless it has first undergone appropriate treatment and purification to ensure its quality and safety.

The water we refer to as domestic water can be of varying quality, depending on its source and use. Rainwater or the water from a shower or washing machine, for example, may contain impurities or pollutants that make it unsuitable for human consumption.

It is important that domestic water is used only for appropriate purposes. Make sure it is suitable and safe for each specific purpose. If you are not sure whether the domestic water is suitable for a particular purpose, it is better to use drinking water.

Yes, it is possible to treat industrial water and bring it to drinking water quality. There are various technologies and processes that can be used to treat industrial water, such as membrane filtration, reverse osmosis, ozone treatment, UV irradiation and chemical treatments.

The exact type and extent of treatment depends on the quality of the source water and the requirements of the end user. However, treating industrial water to drinking water quality is usually more complex and expensive than treating surface water or groundwater because the source water often contains higher concentrations of contaminants.

The cost of domestic water can vary widely by region and provider and depends on a number of factors, including the type of domestic water, the amount of water needed, infrastructure, and operating costs for water treatment.

When it comes to using rainwater or treated wastewater for watering plants or flushing toilets, the cost is often lower than for drinking water because no extensive treatment is required. In some cases, these alternatives can even be free if the rainwater is collected on one's own property or if there are local initiatives that promote the use of domestic water.

There is often an additional cost for using treated wastewater as domestic water, as it is usually more expensive to treat and distribute than rainwater. These costs can vary by region and provider and should be checked with local water utilities if needed.

Industrial water and drinking water are both types of water, but they differ in composition, quality and use.

Drinking water is suitable for human consumption and must therefore meet certain requirements set by the Drinking Water Ordinance. For example, drinking water must be free of pathogens, chemical contaminants and other potentially harmful substances. It is provided by local water utilities, which ensure that it meets the required quality standards.

Industrial water, on the other hand, refers to water that is not intended for human consumption and can be used for various purposes, such as watering plants or flushing toilets. Industrial water can come from a variety of sources, such as rainwater, graywater, or treated wastewater.

Rain strength and roof size

The percentage of rainfall collected by WISY filters (i.e. their efficiency) depends on the amount of water coming through the pipes. In heavy rain (with a lot of water), the efficiency is lower than in light drizzle. Also, the connected roof size has a direct impact on the amount of water and thus the efficiency.

Averaged over the year, 90%.

All WISY rainwater filters are designed to collect approximately 90% of the rainfall on an annual average and use 10% to flush the stainless steel filter insert to keep it clean.

The majority of individual rainfall events in the temperate climate zone (Europe) is rather light. Here, the efficiency of the filters increases up to 99%. Heavy thunderstorms have only a very small share of the annual precipitation.

Moderate climate zone or tropical climate?

The roof area that can be connected for the use of rainwater depends on the local rainfall, since, for example, in the tropics, significantly different values are to be expected than in temperate climate regions.

But there are also considerable differences within a climate zone. The decisive factor is the diameter of the drainage pipes.

The architect plans the pipe diameter

When constructing a new building, the diameter of the drainage pipes is determined by the architect or designer. He takes into account the local climate conditions and the size of the connected roof area.

Determine the diameter yourself

If the rainwater filter is installed subsequently, the diameter of the existing pipes is decisive. Depending on the installation position, it can be the (almost) horizontal sewer base pipe (KG pipe) in the ground or the vertical downpipe.

At the channel base pipe

KG pipes are standardized in the DN standard to match our rainwater filters. The outer diameter of the pipes is decisive for a precisely fitting connection. It is often indicated on the pipe or can be measured with the sliding gauge.

At the downpipe

If the DN specification is not directly on the downpipe or pipe clamp, you can measure it yourself. The following article explains the easiest way to do this:

Determine downpipe diameter

Clocking pump:

If the stormwater utility pump cycles on and off at very short intervals, the cause may be a leak in the connected plumbing system. For example, a running toilet flush, a dripping faucet or a leaking lawn sprinkler.

In these cases, the automatic switch of the rainwater plant registers the pressure drop and properly switches on the pump. But because the flow is too small, the pump switches off again a short time later.

Check the piping system and the connected tapping points for leaks and eliminate them. This usually also ends the clocking of the pump.

Eliminate the cause, because continuous clocking damages the pump.

The simple answer is: yes, rainwater is harmless to health.
RRainwater is evaporated water, comparable to absolutely pure, distilled water. On its passage through the air and when draining over the collection surfaces, the absorption of impurities is rather low. Extensive scientific studies have been carried out on this, such as those by Holländer, R. et al. (1996).

The authors found that "if precautions are taken, such as strict separation of the drinking water and rainwater pipe networks, labelling of the pipe system and the tapping points [...] when [rainwater] is used as service water in the household (flushing toilets, washing laundry, watering the garden), there is no hygienic risk" from the rainwater collected in cisterns. [1]

A total of 1600 water samples from 102 different cisterns were used for the representative study.


[1] Holländer, R. et al..: Microbiological-hygienic aspects of the use of rainwater as process water for toilet flushing, garden irrigation and laundry washing. Das Gesundheitswesen, Heft 5/96, Georg Thieme Verlag, Stuttgart, New York.