I am saving 300 Litres of water per day.
I simply made an adjustment to my grey water pipe
with a few PVC connectors.
This was then directed into a tank
(which I got second hand)
Now I can water my garden with no extra cost.
The thin pipe comes from baths/basins,
the thick one is the black water pipe from the toilet
(DO NOT tamper with the thick pipe).
Once a week rinse out the grey water tank with some
clean water so that new grey water can stay fresher for longer
Try and use the water up within 3 days so it doesn't go stagnant / smelly.
Attached is an image to show you how easy it is.