In years gone by the  water pump was not considered an important part of a rainwater harvesting system. Rainwater collected and stored in barrels only being used for gardening and other outdoor work that didn’t require crystal clear water.  Today water pumps are considered essential when it comes to building a rainwater harvesting system. Following the evolution of some other components of rainwater harvesting systems allowing a purpose-built system to purify rainwater – remember that the rainwater that falls on the roofs of houses seems clean but it actually isn’t, with the water picking up a vast number of impurities in the atmosphere as it falls.

By utilising a water pump clean rainwater can be distributed to other parts of your home or property.  But not all pumps are the same and choosing an incorrect pump can lead to problems like low water pressure.  So how can you ensure that you choose the right pump for your system?  Getting the right pump simply means gaining knowledge on the following specs and features.

Suction Pressure

The specification known as suction pressure is often marked clearly on water pumps. Often its unit of measurement is in metres.  What exactly is suction pressure?  The pump inlet where the water enters from the tank is what’s considered the pump suction area. Suction pressure is the amount of water the pump is able to suck in through the inlet. Numerous pumps in the market indicate suction lift (measured in meters), which is how far the pump is able to suck water up into itself. 

How strong of suction pressure do you need to have?  Well the strength of the suction pressure depends on the rainwater harvesting system on your property and the location of the pump in respect to the tank.  If you have a large underground water tank on your property you may either have a pump to go along with it or alternatively you can install a more maintainable and accessible pump on the surface that’s above the tank. If tank base is located five metres below the pump, a pump that has an eight-metre suction lift can easily suck water from tank before pumping it to areas where water is needed. 

If your property is located on a steep slope your pump is better off positioned in a spot that is higher than the tank.

Water Flow Rate

Flow rate is another feature to be aware of. Flow rate from either a shower head or tap is influenced by aerators, water saving heads, and piping. However, it’s important that the pump also be capable of generating flow. The unit of flow is litres per minute. A general rule of thumb is, the higher the volume of water a pump can push through pipes, the higher the number of taps which can be serviced.  Other factors that influence flow rates are elevation, pipework, and access points.

Maximum Flow Rate – Maximum flow refers to how many litres a pump can immediately pressure from itself without having to go through pipework. In other words, this is the volume of water that can be directly pushed out the pump.

Rated and Normal Flow Rates – Quite simply rated flow is the normal operating condition the pump is built for. Another term, normal flow, often is less than rated flow. Normal flow represents conditions your pump is supposed to operate much of the time.

If you find a pump which lists both, pay more attention to normal flow.


Head is another specification or feature of a pump. It refers to how much pressure the pump is capable of handling vertically. This is something you need to be aware of since it’s most likely that the source of your water and your pump are lower than their access points on the property. Intuitively, a pump which exerts additional pressure must be capable of pumping water higher, and therefore must have higher head.

Rated and Maximum Head – Rated and maximum head have a couple of different values. To explain what both mean, one example would be to a look at a pump with a 35-metre maximum head. This means that a pump is able to pressurize water to that particular height under ideal setup conditions.  Maximum head, is defined as the maximum height a pump can operate before it can longer able to pump water. The thing is, it represents ideal setup conditions. There are so many bends in your house’s plumbing, and all of these have an effect on maximum head pressure.  At this point, it becomes important that rated head be observed as well. Rated head is the best height the pump can operate.

For more information or a quote to upgrade or install your rainwater pumps contact Alpha PMS today

Related Tag: Grundfos Pumps Gold Coast