Water, Water Everywhere

Water, Water Everywhere

So, just in time for the heatwave that’s forecast to hit the UK, I’ve installed an irrigation system.

Now, we don’t have a particularly big garden, so the idea of installing an automatic irrigation system might seem like extreme overkill. But of course, it’s a great big gadget that needs tinkering with, so I was interested.

The idea is that there is an electronic valve, called a solenoid, attached to a pipe connected to the outside tap. This controls the flow of water, which is then connected to a loop of pipe that runs around the perimeter of the garden. At four main points around the garden (pretty much the corners) there are short lengths of pipe that split off from the main feed that run to four pop-up sprinklers.

There are several different types of sprinkler, each using slightly different methods to distribute the water over the ground. In my case I was limited by the available flow-rate, the amount of water that passes out of the tap per minute . I used a standard petrol can to measure the flow-rate available to me. It took about 18 seconds to fill the 5 litre can, so I worked that out to be about 18 litres per minute. Many of the more simple fan design type sprinklers have quite a high flow rate, in the region of 4-6 litres per minute, so if I had four of those, I’d be hitting my limit pretty quickly.

Then I chanced upon some ‘rotator’ nozzles instead. The Hunter HP 2000 nozzles produce several thin streams of water, at varying trajectories. The picture at the top of this post shows one of the heads while it’s running. They use the water pressure to rotate the head to provide even coverage over an adjustable arc of up to about 6 meters. Crucially, the rotators were specified to need only 1-3 litres of water per minute, so they were ideal. Plus they look cool when they’re running.

I think pop-ups are generally intended to be used in lawns where the ability to drop down out of sight is desirable, in fact you can even run the mower over them. But I liked the idea of them disappearing out of sight when not in use even though they’re in the borders of our garden.

I ignored most of the advice I’d read and also included some simple ‘micro misters‘ like those you’ll probably find in your local DIY store. They sit on spikes and just hammer out some water over an arc. These were to fill in some edges and gaps around the patio that couldn’t be covered by a pop-up.

The next stage now is to hook an Arduino (or possibly even a Raspberry Pi) up to a relay controlling the power to the solenoid. This will mean that the whole thing can then be switched on or off automatically. The ultimate plan is to get a rain meter hooked up to it too, so it can postpone the watering program if it’s rained in the past 24 hours or so.

I’ve also ordered a water flow sensor, which I’m hoping I can hook up to the Arduino too, in order to measure the amount of water that’s dispatched during each watering session.