Invest in a water butt, cheap, easy to install and after a little rain you can have 100 litres or more rain water stored for as and when you need it.
I have 2 x 100 Litre butts currently chained together and we are looking at buying a 200 Litre one for the front garden too as the 2 currently at the rear also serve as a top up tank for our garden pond.
For example, I emptied both the water butts this morning to top up the pond, after an hour and a half maybe of rain both are filled up to the brim again and ready to go.
I'll use maybe 10 or 20 Litres of water on a hot day when it has not rained for watering seedlings, my Bonsai, other trees, saplings, shrubs and plants in and around the garden and in my greenhouse so I have a good 10 days supply of water easily if we have a heatwave. Which is fairly rare in the UK and based on the weather this "so called" summer so far; I won't be worrying any time soon about running out of water that is perfect and natural for my Bonsai and Seedlings.
We are literally gob-smacked by how fast the water butts fill and we have the 2 installed off of only the rear drain pipe, when we get the one for the front that will fill from the front drain pipe so no matter which way the rain comes in we will be collecting water at a fair old rate.
The water butts we bought cost us £28 each and came with drainpipe filler, tap, lid and stand & were fitted in minutes. I honestly cannot see it being long before they literally pay for themselves at the rate they do their job.
