Sucking Water from an Underground Tank

The inlet of your pump, where water enters in from your tank, is considered the suction area of a pump. Suction pressure is how much water your pump can suck in through its inlet.

Many pumps specify a suction lift, represented in metres. This represents how far down your pump can lift water up from.

All our pressure pumps have the suction depth displayed (in the description or additional information), so please check the suction depth before you purchase the pump to make sure the suction depth is enough for your application.

Most standard pressure pumps will have a maximum suction depth of around 6-8m.  Keep in mind that this is a maximum suction depth.  This means that the flow (litres per minute) will reduce the greater the depth.  Add your suction depth to the head performance of the flow chart.

Surface Pressure Pump

A surface pressure pump sits on the ground above the tank. The pump sucks the water up from the underground rainwater tank.  It is important to have only one pipe with only one elbow from the tank to the pump.  Never install a T-piece instead of an elbow as air bubbles can get caught in the T-piece.  You must also install a quality foot valve at the bottom of the suction pipe so the pump does not loose prime.

When calculating the head, add your suction depth (in meters) to the head performance on the pump’s flow chart to get the total head.

Surface Bore Pump / Convertible Jet Pump

If you need to suck water up from greater depths, for example a deep well or bore, then you will need to look at a convertible jet pump which is also called a surface bore pump. It uses a venturi system with 2 pipes that need to be primed at all times. They push water down the hole through one pipe then through the venturi which forces water up the other pipe and back into the pump for discharge.  They can handle a max depth of 50m.