It is estimated that each person consumes an average of about 150 liters of high-quality drinking water per day. But it turns out that its consumption can be reduced by almost one and a half times, and without prejudice to comfort, and only through the rational use of it and the use of simple technical means. These include, for example, the installation of water-saving fittings and taps with water flow limiter, the use of modern washing machines and dishwashers.
In everyday life for drinking and cooking is only a small part of the total consumption of drinking water. Its larger volume is used for household needs: toilet, laundry, watering plants. Here it can be replaced by rain, with savings of up to 40-50%.
Rainwater meets all existing hygienic requirements and is quite suitable for economic use. However, there are some limitations in its application.
Collection and use of rainwater
Rain water flowing from the roofs is discharged through the filter into the supply tank and from there by means of a pump to the consumers. When the tank is not filled enough, for example, during a drought, it is automatically replenished with drinking water. The system is simple, but for its smooth functioning requires constant monitoring.
Device for collecting and using rainwater: 1 – water level sensor in the collection tank; 2 – fine water float filter; 3 – water level meter; 4 – multistage centrifugal pump; 5 – polyethylene collection tank; 6 – siphon; 7 – self-cleaning vortex filter.
In principle, it is possible to collect rainwater from any roof, and its amount largely depends on the type of roof. So, green roofs (with grass cover) roofs take a significant part of water for themselves, and its remaining part is saturated with organic impurities that can stain water. To use such water, for example, for the washing machine, it is impossible.
A similar effect on rainwater and have roofing on the basis of bitumen. Water collected from the metal roof is not recommended for irrigation of edible plants. The most acceptable in this regard, the roof, covered with clay and concrete tiles, slate, glass.
System for charging the supply tank, which can be equipped with a water level sensor (manufactured by Intewa).
At the very beginning, rainwater passes through mechanical cleaning filters that separate dirt, moss, foliage and bird droppings. Due to accumulated dirt, they must be constantly cleaned. There are quite effective self-cleaning filters that do not require special care, but do not exclude water loss. Both filters can be installed both on drainpipes and on the ground. The choice of filter depends on the roof area and the number of drainpipes: if there are few pipes, filters are mounted on them, if there are many, on the ground.
The rainwater entering the tank is further purified by sedimentation of small particles of dirt. If necessary, it can again be passed through a filter installed in the area between the pump and the consumer.
It is important to choose the right place to install the collection tank. The inner tank of opaque plastic can be placed in the basement of the house, but it takes quite a lot of space. It is better to put the tank outside the house, lowering it into an open pit. In this case, it will meet the requirement of storing water in a dark and cool place. Such tanks can be made of plastic or in the form of concrete tanks. It is advisable to dig a hole for the outer tank at the same time as the pit for the house under construction. When installing a rainwater harvesting system in an already built home, it will be cheaper to put a collection tank in the basement.
It is important that the water enters the tank without raising the sediment, and it is better to select it for later use from above. To remove dirt and avoid overflow, a suitable hatch and siphon should be provided in the tank for draining excess water, for example, during prolonged rains.
Water supply to consumers
One of the important elements of the system for collecting and using rainwater is a pump that supplies it under pressure to consumers. In most cases, this is done using a water-supply house machine – a pump that is turned on when water is taken. Often use water supply station (with a pressure tank) with centrifugal pumps, characterized by a smooth running, low power consumption and high corrosion resistance. If there is no water in the collecting tank, the pump automatically turns off. By performance, the pump should be selected taking into account the capabilities of the system for collecting and using rainwater.
Concrete tank for collecting rainwater. Capacity of standard tanks – from 3 to 9.5 m3.
Hydria drinking water collection system from Zapf. The capacity of the collecting tank, which serves simultaneously as the foundation of the garage, is 22 m3.
When laying pipes for domestic water supply, it is necessary to exclude contact between the pipes of rainwater and drinking water, and control the drinking water supply by means of a magnetic valve and a float switch. For water supply, it is preferable to use recyclable and corrosion-resistant pipes made of polyethylene or polypropylene. The use of copper pipes is unacceptable, the rest are subject to labeling.
Polyethylene tank for collecting rainwater installed in the pit. Tank capacity – 5.5 m3.
Parameters of the system for collecting and using rainwater
Calculation of system parameters can be made independently. For this, the expected amount of collected rainwater and the need for it for household needs should be taken as a basis. The first of these two indicators depends on the area of the roof projection on the ground, the amount of precipitation (according to the weather service) and the coefficient of water outflow, which is determined by the type of roof and water losses during its filtration.
According to DIN standards applied in Germany, rainwater sampling points must be labeled or labeled.
The need for water for household needs can be determined based on the number of families. It is quite enough that the volume of the collecting tank is about 5% of the water that is drained from the roof. This is quite enough to “hold out” without precipitation for several weeks. If you install a smaller tank, the probability of its frequent overflow is high.
On a note: Fear of infection is not worth it. Studies conducted by the State Institute of Hygiene (Bremen) and other organizations suggest that rainwater can be safely used for household needs. At the same time, to prevent the development of algae and bacteria, the container with rainwater should be located in a dark and cool place.
Compliance with environmental requirements
The desire of some homeowners to use rainwater is most likely due to their desire to contribute to improving the ecology of the environment. Therefore, in some European countries, local authorities encourage this initiative.
Self-cleaning filter mounted on the drain pipe. Dirt retained stainless steel mesh.
At the same time, for the construction of such a system, for example, in Germany, the permission of local authorities is necessary. Regardless of whether the system is equipped with an external or internal collection tank (the latter is cheaper), its payback period is quite long, including due to the growth of water tariffs.