The pump plays an essential role in the functioning of the cistern. It is the heart of the rainwater system. What requirements must pumps for cisterns meet? We have put together 12 tips for choosing a pump.
Table of Contents
Before installing a cistern, you should check the individual requirements and clarify how the water can reach the consumer. Basically, this is possible in two ways:
- with a submersible pump
- with a suction pump
Submersible pumps are lowered into the water basin. So they are surrounded by the water they are supposed to carry. To bring the water to the place of use, a hose is therefore laid outside.
Suction pumps are installed outside the water basin. They are equipped with a suction hose that is placed in the water. This is how the water is transported.
12 Notes on pump selection
1. Check requirements
Check before pump selection
- the required flow rate
The flow rate describes how many liters of water can be pumped through the cistern pump per hour.
- the delivery height to be overcome
The head is the maximum height difference between the water surface and the consumer.
- the required delivery pressure
The pump can generate 1 bar of pressure for every ten meters of height. The lower the head, the more pressure is available at the point of consumption.
- the suction height to be overcome (when using suction pumps)
The suction height characterizes the difference in height between the water surface and the pump.
2. Calculate delivery rate
Bear in mind that the flow rate decreases as the flow rate increases. When operating a cistern pump over a large difference in height, the specified maximum delivery rate is not available.
3. Consider antifreeze
The installation of suction pumps is carried out outside the pool. In winter it is important that the delivery lines are completely drained so that they cannot burst. The pump is then dismantled and placed in a frost-proof winter quarters.
4. Consider height differences
When using suction pumps, the difference in height between the water surface and the pump may only be eight meters. Otherwise, preference should be given to submersible pumps. These can handle greater delivery heights.
5. Note space requirements
Submersible pumps are space-saving because they disappear in the water tank and do not require any space outside the cistern. In the case of cisterns with a small capacity, on the other hand, suction pumps are advantageous. Because they are installed outside the cistern, they do not require any additional space in the tank.
6. Consider material differences
Pumps in cisterns mainly consist of an electric motor and a pump head. The housing is made of cast iron, plastic, steel or stainless steel.
Usually rainwater is transported. This has a slightly acidic pH value, so that parts made of steel or cast iron are affected by corrosion in the long term. Stainless steel and plastic housing are corrosion resistant and more durable.
7. Calculate volume
Submersible pumps work under water and are therefore significantly quieter than suction pumps. Before you buy, consider that suction pumps make running noises throughout their entire service life. This can be very annoying.
8. Include maintenance work in the planning
From time to time, cistern pumps require maintenance or repairs. Keep in mind that submersible pumps are less accessible than suction pumps.
9. Consider the size of the cistern and the number of consumers
Suction pumps are suitable for cisterns with a storage capacity of up to 5000 liters.
On average, three tapping points can be supplied. Choose a submersible pump for higher requirements.
10. Relate the delivery height and pump pressure
The higher the pressure that the pump can build up, the greater the head that can be handled. A pressure of 1 bar is required for every ten meters in height. Suction pumps can build up a higher pressure than submersible pumps.
11. Ensure compatibility with garden irrigation
In order to water the garden or property, owners usually use hoses or pipes. Make sure that your cistern pump is compatible with the common hose and pipe systems.
12. Pay attention to robustness against environmental influences
A safe functionality must be given even with contaminated rainwater. In addition, the cistern pump should be insensitive to algae and all components should work steadily, even with temperature fluctuations and high humidity.
frequently asked Questions
The rainwater flows from the gutter via the downpipe into the retention basin, the cistern. A pump is used to transport it from the cistern to the end devices, such as the washing machine, the toilet or the garden for irrigation. When using a suction pump, the water is sucked in. Submersible pumps, on the other hand, push the water upwards.
Pumps intended to pump water from deep wells or cisterns must be fitted with an additional pressure switch. This has a metal membrane that reacts to the water pressure at the hose connection. When you open the hose, the pump turns on automatically. Closing the hose changes the water pressure and the pump switches off automatically. An integrated pressure switch increases the price of the cistern pump, but it makes a lot of sense.
Pressure switches are integrated in many cistern pumps. On models that do not include a pressure switch, this can be retrofitted in front of the pump.
Submersible pumps are equipped with a rope that can be used to lower them into the water and bring them up again.
The pumps contain a filter system that filters out dirt particles from the penetrating water. However, if you want to use heavily polluted water for garden irrigation, for example, you should prefer a dirty water pump.