Automated irragation

Yes at some cost. How much water and money will you save doing this? How much will it all cost?

Of course. But much cheaper to just connect the mains to the irrigation system and forget about the butt and the pump.

I am not saying that saving water is a bad thing but at the scale of a water butt (200 l ?) you are paying lots of capital costs and getting little return. You would be doing this for ideological reasons probably not for saving money.

Do your sums first.

David

Get as large a butt as you can to make it worthwhile. Also, check the specifications of the irrigation timers to ensure that they will operate properly from a low water pressure. If you can mount the butt up fairly high, that might help.

All you need is a ballcock-type valve (as used in a toilet cistern) placed as near as possible to the bottom of the water butt (but where it can still open a little). The valve will then only open when the butt is nearly empty, but will not allow mains-water in when there is even a small amount of rain water in the butt.

To be perfectly honest for a "little" courtyard that's "so small" it wouldn't be worth the time, effort, and expense to automate watering for a couple of raised beds... I strongly suggest using a garden hose betwixt the times it rains directly into your beds... diverting water from your roof tops would probably be enough to drown your beds and your entire system... unless one resides in an arid clime I don't see the point.