Connecting Multiple Tanks

Here are some helpful guidelines when linking multiple tanks. Planning your rainwater harvesting system using this method maximises your available water without having to manually switch between tanks or install a transfer pump, so you will end up with the simplest possible system.

Align tank overflows

First, align the height of your tank overflows. Identically sized tanks are straightforward, but smaller tanks need to be raised to meet the overflow height of the largest tank in the chain.

Only one overflow in the chain is required (must be at least as large as your downpipe), so the remaining overflows can either be capped or connected to stormwater. Multiple inlet pipes require sufficient overflows to match the incoming flow.

Link the lowest outlets

Link the lowest outlet of each tank with suitable flexible hose. Melro tanks are supplied with valves, and we recommend you use these to control the water from each tank. In a tank chain of three or more different sizes, start with the smallest (most elevated) tank and connect to the next largest tank in sequence.

Tap off the lowest tank

Water from all tanks will now drain into your largest tank during normal use. Simply connect your pump (or hose for gravity fed systems) to the bottom outlet of this tank.

Multiple Tank Connection Examples

Same sized tanks

Both tanks in this image are the same height, so only a simple connection is required. Water flows into the first tank which has a matching overflow connection. You can choose to tap from either tank because the water level will continually equalise between both tanks.

Connect same tanks

Different sized tanks

The smaller tank in this image has been raised so that both overflows are at the same height. When the first tank fills above the base of tank two, the water level will then equalise between both tanks. As water is used, water from the smaller tank will drain into tank one. You only need to tap off the first tank.

Connect different tanks