Requirements for pumps for cisterns: 12 references

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.

Install cisterns

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.

Tip: Hand-operated pumps can also be used to transport water from the cistern. They are equally practical and decorative. In contrast to modern cistern pumps, it is operated solely by muscle power. They are excellent for transporting small amounts of water.

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.

Note: Select the flow rate so that sufficient water can be removed from all tapping points. Domestic waterworks that have an intermediate storage tank get by with a lower flow rate.

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.

Tip: Many manufacturers provide overviews in which the delivery rate can be seen as a function of the delivery height. Also note that the number of consumers increases the required flow rate.

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.

Tip: Keep in mind that the delivery head changes depending on the water level. To be on the safe side, use the bottom of the cistern as a reference point for the dimensioning. In this way, the water supply is secured even when the water level is low .

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.

Note: Plastic housings are by no means inferior to stainless steel housings. They also convince with a lower volume .

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.

Kira Bellingham

I'm a homes writer and editor with more than 20 years' experience in publishing. I have worked across many titles, including Ideal Home and, of course, Homes & Gardens. My day job is as Chief Group Sub Editor across the homes and interiors titles in the group. This has given me broad experience in interiors advice on just about every subject. I'm obsessed with interiors and delighted to be part of the Homes & Gardens team.

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