It's amazing: we are so fixated on water from the faucet that we hardly think about other water sources. One of the most important of these is greywater.

Greywater is obtained by treating slightly polluted water that accumulates in the household – for example, when showering or doing the dishes. It is not potable, but you can use it without hesitation for the toilet, the washing machine or for cleaning, for example, to reduce your drinking water consumption. Depending on the situation, you could even use it to water plants or flowers.

Everyday tips for using rainwater and greywater without large investments

There are simple and inexpensive ways to use greywater and rainwater every day. With these tips, you can conserve resources and save money at the same time without having to make a big investment.

Collect rainwater

Collect rainwater in rain barrels or buckets: Place them in the garden or on the balcony to collect rainwater. You can use this to water plants or to clean garden tools and furniture.

Collect cold water

While you're waiting for the water in the shower or at the faucet to get warm, you can collect the water that normally flows down the drain in a bucket. Use this water to flush the toilet by pouring it directly into the toilet bowl, or water houseplants.

Reuse cooking water

After you cook vegetables or pasta, the cooled cooking water can be used to water plants. It contains additional nutrients that will benefit their growth. However, make sure the water does not contain salts or oils that could harm the plants.

Collecting water from the air conditioner

Might sound a bit far-fetched, but many air conditioners produce condensation that is usually drained away. You can capture this water and use it to water your garden or clean outdoor areas.

Domestic water treatment on a large scale – here's how it works

Although greywater is well suited for flushing toilets or watering gardens, drinking water is still usually used for these applications – what a waste! To use graywater instead,you need a greywater system. This must be separated from the drinking water circuit to avoid contamination.

A domestic water system uses special filters to treat the water for re-use. To prevent legionella from forming, it is also necessary to heat the water to at least 65 degrees Celsius. This applies even if you want to use domestic water for the washing machine. Otherwise, especially when rinsing with cold water, harmful germs cannot always be eliminated.

Is a greywater system worthwhile for your household?
A greywater recycling system costs around 5,000 euros without installation. Nevertheless, depending on the water consumption of your household, such a system can be financially worthwhile – especially if you frequently do laundry or many plants need to be watered.

By installing a domestic water system, you can save up to 70 liters of drinking water per day and per person in your household. For a family with two children, that's quite a lot – about 8,400 liters per month. This is not only good for your wallet, but also for the environment. In addition, depending on where you are based, you may be able to get subsidies from the state. This reduces investment costs. However, it is still best to decide whether a graywater system is worthwhile for your household by compiling an individual cost-benefit analysis.

Collect and use rainwater – not just for watering flowers

Everyone knows what rainwater is, of course – but many people still don't think about using it. But it's quite simple. You can collect it and use it to water the plants, as mentioned above. Rainwater is more suitable than drinking water from the faucet, because it does not contain lime.

While watering plants with rainwater seems obvious, there are concerns about other fields of application. These are primarily based on the question:Is the use in the household hygienic and harmless to health? After all, rainwater may come into contact with pollutants in the air or become contaminated in the gutter on the roof, for example by bird droppings.

So if you want to use your rainwater like graywater in the household, you should definitely ensure its cleanliness by installing a filter system between the catchment area (e.g. downpipe) and the rainwater storage tank (e.g. rain barrel or cistern). Garden centers or DIY stores offer suitable solutions.

The simple answer is that using rainwater is almost always worthwhile. For example, owners of a garden can expect to use several 10,000 liters of water to irrigate their property over the course of a summer. This water consumption can be covered, at least in part, with rainwater, thereby reducing drinking water costs. For this type of use, the investment costs for a collection system are also very manageable.

The bottom line

The use of rainwater and recycled greywater in the household and garden can significantly reduce the mindless consumption of valuable drinking water and save costs.

Together with other water-saving measuressuch as the installation of water-saving faucet aerators and flow regulators in the kitchen, bathroom or office, the use of rainwater and gray water is another step towards saving one of our most valuable resources. In this way, many small steps help with the big social goal of protecting the environment and the climate.