Garden Watering System – Part 2 – Pipes

In Part 1 I introduced my new garden watering system and the components used to switch water on and off. In this post is more detail on connecting the pipes and other hardware parts needed.

I put the master solenoid valve directly on a tap, using  a 3/4″ to 1″ adapter. After a while, I added a 2x adapter so that I could use a hose on the tap too. I used a brass adapter because plastic ones I’ve used previously degrade quickly in the sun. Having the master valve on the tap ensures that the pipe to the main valve manifold is not under pressure when not in use, and lets me locate the main valve manifold at a more convenient location than right next to the tap.

Master valve on tap

Master valve on tap

master valve on tap with adapter

Master valve on tap with brass tap adapter

Having the master valve directly on the tap means there is no water pressure in the buried pipes when the system is not in use, and only one potential failure point instead of four. Also, both the master valve and at least one of the other valves have to be on for water to flow. I’ve seen designs that have the watering system connected directly to the main plumbing, but I’m not comfortable burying a main line that is always under pressure, and that would mean you can’t work on the valves at all without turning off the water supply to the house. In that kind of a design, a fault in single valve would result in wasted water and potential flooding.

From that master valve, I have used rigid 25mm PE (poly) pipes with screw-on connections down to ground level, where the last one is screwed into a 1″ PVC pipe. This goes under a path and through a couple of turns until it comes up above ground five metres away, where it joins to a 19mm poly pipe filter and 30cm length of pipe that joins to the solenoid manifold which the solenoid valve for each watering zone is attached to.

Master valve connection to PVC pipe

Master valve connection to PVC pipe

My grandfather recommended I use PVC pipe for the first section, but I’d never worked with it before so I wasn’t that motivated to try it out. So for the first version I used 19mm poly pipe. This reduced the available water pressure quite a bit (not good!) and I could see the poly pipe slipping off the barbed joins (also not good – if they come off all the way, they will waste water). So I finally bought some 1 meter lengths of PVC, some right angle and straight joins, a pipe cutter, cleaning solvent and glue. It is really amazing stuff to work with. It’s no harder to push two pieces of PVC into a joiner and glue it than it is to push two pieces of poly onto a joiner and clip it, and it gives a much stronger result. I should have listened to my grandfather in the first place!

Each solenoid has a 25mm threaded inlet. So to join to this I used 25mm to 25mm/19mm threaded poly joiners (some are 19mm on the outside, some are 25mm), and then 19mm/13mm poly pipe barb to 25mm/19mm threaded adapter depending on the diameter of the pipe for the zone and whether I had used a 19mm or 25mm thread. Always buy extra of this sort of thing – I had to go back to the shop more than a couple of times because I had miscalculated and run out!

Solenoids in final position. Bricks underneath are to stop them sinking into the ground, you never know when you might have to change something.

Solenoids in position and connected. The wires are plugged into a terminal block (on right), the wire to the controller goes into the other side of the terminal block.

I had a couple of joins that kept spraying water – in the end I took them completely apart and found that a rubber gasket was missing. These fall out and are hard to spot among grass, so take care of them. No amount of Teflon tape wrapped around a thread can make up for a missing rubber gasket/washer!

In the end, I was still worried about the plastic clips on the poly barbs, so I added some metal screw-tightening grips, and then used hot melt glue over the top. Those connections haven’t moved since! I tightened them to the point of starting to dig into the poly. I wouldn’t do it much tighter because that might break the barb inside.

To get under the path I tried digging, I tried a hose. In the end what worked for me was getting a 60mm piece of PVC, cutting the end at an angle, and then rotating and pushing that pipe as hard as I could. Then I used a shovel to level it in. It cut a core through the clay which I then pushed out with a stick. Once that pipe was buried under the path, it was easy to push the smaller 1″ PVC pipe through. The wire to the 4 solenoids also goes through the larger pipe and is then buried next to the small pipe.

pipe and wire going under path

Pipe and wire going under path

Pipe and wire coming out from under the far side of the path

Pipe and wire coming out from under the far side of the path

Pipe and wire coming out from under the far side of the path - 2

Pipe and wire coming out from under the far side of the path

Pipes in ground, ready to be buried again

Pipes in ground, ready to be buried again

Water inlet pipe where it comes out of the ground to provide water to the solenoid valves. If I was doing this part again I would make it come up a lot closer to the valves.

Water inlet pipe where it comes out of the ground to provide water to the solenoid valves. If I was doing this part again I would make it come up a lot closer to the valves.

That’s the big picture with the watering zones. The main pipes for each zone have to go to where the plants are that you want watered, and then sprayers or drippers can be attached. You will probably have to adjust the pressure on each zone individually, depending on the length of the run and how many drippers and sprayers are on it.

 

Stay tuned for part 3!

Author: Paul

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