Increase your raintank’s holding capacity #2

Like theĀ previous method, this method raises the level of the overflow before it reaches the overflow pipe that runs to your stormwater. Unlike the previous method though, this one is adjustable and doesn’t restrict the outlet at all. It uses three 90 degree bends (one of which you are using already) to create an adjustable dogleg which allows you to set the height of the overflow and, thus, the height of the water stored in your tank.

How to do it-

Assemble these pieces.
Assemble these pieces.

Start by sourcing 2 x 90 degree bends. and two short pieces of pipe to join them. You will already have the the third one connected to your tank and existing overflow pipe.

Arrange them like so.
Arrange them like so.

You will need to join the pieces together to make a dogleg like in the picture. Don’t use glue for this project because you will be needing to twist things around a little. I’ve included a third bit of pipe in the pic to show the complete thing. You won’t use this because it will be replaced by your overflow pipe.

Fit the assembly to the tank and you're done.
Fit the assembly to the tank and you’re done.

Fit the assembled pipes to the outlet on the outside of your tank and downpipe as shown.

Twist the new bends so that the (horizontal) joiner in the centre is at the same level as the desired water level in your tank.

You can now increase and control your water level.
You can now increase and control your water level.

You can see that you have created a restriction that the outflowing water must climb to before it can flow into your stormwater pipes, this effectively raises the water level in the tank.

Don’t set your level too high, though, or the water in the tank will flow out through the inspection hatch and cover on the top of the tank and flood the ground around the tank. You still need the water to be able to flow away.


Capturing and storing as much water as possible whenever we can is the only way we can keep gardens and home food production going. The extra litres saved may not seem like a lot but all of the climate projections point to less rainfall coming in heavier downpours because the warming atmosphere can hold more water and is more reluctant to let it go in small amounts. Because global heating adds a degree of uncertainty to any projections, we may see increased localised rain in some areas but, overall, things will be drier. Saving water will become a necessity.

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