This year, as well as the greenhouse, we’ve actually got round to putting in some veg. Added to the flowers in the borders, when it’s hot, it gives quite a watering load – it was taking an hour a month ago. That was such a lot of time that I thought it was worth automating some of the watering. So, for a few weeks I’ve been playing. Some things have worked, some have not worked at all, so I thought I’d jot down some notes to help others who may try the same things.
Micro-irrigation in the greenhouse
As well as the hydroponic stuff, we’ve got various things in grow-bags in the greenhouse. So, I wanted to water these using a micro-irrigation system I bought and had success with in the last house we had in Farnham. But, it is designed to work from mains water … which we don’t have in the greenhouse. However, we do have a 12 volt battery powered system to run a flood and drain hydroponic set-up (see here). Last year I used the second timer circuit to run a pump to ensure another hydroponic system was topped up once a day. But, I managed to insert a side-branch, made from micro-irrigation tubing, in the flood and drain pump circuit that puts a dribble into the other hydroponic troughs, and a couple of weeks trials has shown that it keeps them topped up nicely.
So, I now had a spare circuit and pump (a 10 litre/minute caravan water feed pump from ebay) that could do duty to run the micro-irrigation system. This is now working superbly, though trying it out led to a couple of discoveries. Firstly, the pressure that this little pump can throw out is impressive – I had assumed that I could manage without the 1 bar pressure regulator (that I planned to use elsewhere), but there were leaks everywhere. Putting the pressure reducer in sorted that out. Secondly, I had two branches – one at floor level for grow-bags, and one above the staging, to use for plants in pots. The pump only needed to run for a minute or two in total, but when it was off, the upper branch drained back down again, and when empty took several minutes to prime (i.e. it didn;t during the time the pump was on. You can’t get non-return valves for this stuff, but I found that if you put the stiffeners that you use with domestic plastic water pipe down the pipe, then it is possible to get brass compression fittings to be watertight, so I was able to use a standard non-return valve. The feed tank for all this was simply another central heating header tank, which has the benefit of being light-tight, so stopping stuff growing in the tank (the tank at the front is the new one, the rear one is the hydroponic sump :-
Gravity powered micro-irrigation in the veg patch
My next foray was to try and water quite a number of potato and other tubs from the water butts, but using only the pressure from the water butts to do so. This was as simple as using micro-irrigation tubing connected to a timer that was connected to the water butts. I found a two-channel water timer in Aldi for only £16 which was a bargin. Actually connecting that to the water butts was a little more tricky. I put short lengths of hose with female hoselock connectors on on each butt, which allowed be to gang several butts together using Y connectors, or split the system if I wanted. These feed a four-way splitter attached to the wall that has the timer on, and also other circuits, such as one to fill a watering can.
I was concerned that the long run (15m) would give an excessive pressure drop, so tried using pressure compensating drippers, but there wasn’t enough pressure to make them drip at all. So, I reverted to standard adjustable drippers, and adjusted the 9 of them together to balance the system. It seems to work well, though it takes a fair while to work – we run it for an hour a day.
The last experiment has been to use soaker hose in a couple of flower beds, and most recently a fair chunk of the veg patch as well. The first test was for flower beds, with the intent being to run it from a sump pump in another water butt on the other side of the house. This was, over a couple of hourse of frustrating and very very wet experimentation, a total failure. The pump, a standard immersion sump pump, simply couldn’t handle any material back pressure down the 1/2 inch hose, and we effectively got no water out. I was really surprised, given the sheer volume of water that comes out of a short hose from this pump, but I guess it was a good reminder that volume is not pressure. So, instead we used an old water timer we had on a garden tap that we recently connected up. This fed one length directly, and via more pipe we laid under the lawn when we put it down. another circuit.
This has worked a treat, though the mains pressure is such that you get tiny sprays coming out of the hose as well as drips. The final experiment (so far) has been to use a chunk of soaker hose directly from the water butts, with no more pressure than gravity gives. I was a little suspicious that this would work well enough (mains only seems to get a bit of water out over time) – but, so far, even with 10 m of soaker connected, it looks good, and it is now on the second veg patch timer channel for a couple of hours a day. You can see the three parallel lengths in the photo below.
And teh joy of this pottering about (and it is just pottering) is that it has taken me less time than the watering would have done – and a lot less water.