I've just bought myself a small plastic covered "greenhouse" thing from the local garden centre. It's great, it does just what I need for a small garden and was cheep too. I'm using it to cultivate some seedlings that I'll be planting out in the garden, but given the unpredictable nature of the English climate, I can't trust them to be totally unprotected from the elements right now. The problem is that little pots and tubs dry out very quickly and I'll be going away for a few days soon. I need an automatic watering system that will stop things from drying out while I'm gone.
Key objectives are:
-Use stuff lying around the house
-Don't spend ages getting it working
-Make sure everything get a good soaking.
-Keep and eye on environmental considerations
-Be Safe - Don't mix water and electricity!
Step 1: The pump and reservoir
I bought the pump a few months ago from ebay. It's a 12v windscreen wiper pump from a ford. I bought it because I thought I'd have a go at making some kind of water feature for the garden, but never got round to it. It will be just the right size for this job. The pump is not submersible so it has to be mounted on the outside of the reservoir.
The ideal reservoir would be a large bucket, but I didn't have one lying around that I could cut a hole in. Instead I had a whole bunch or plastic plant pots that could hold about one and a half litres. These are easy to cut and disposable (or at least their primary use is not affected) if I got it wrong the first time. Their problem is that they have large drainage holes cut in the bottom, which makes them less than ideal for holding water. A simple watertight fix for this is to put a plastic carrier bag inside the plant pot and force the input pipe of pump through a small hole in the bag. As the plastic is a bit elastic it helps to make a water tight seal. The pump has a rubber grommet which goes over the input pipe to create another water seal between the inside and outside of the container. Filling the reservoir with water and placing it on a dry surface shows me that it is not leaking.