You have now the technical study in hand to realize your underground watering system. Now it's time to tackle one of the most difficult parts (for the arms...): the earthwork.
Let's see the steps and our advice for the earthwork for the installation of your underground sprinkler.
1/ The trenches
Make the trenches as shown on the plan
The width does not matter. A trencher makes cuts 9 cm wide and this is more than enough to pass pipes and sprinklers. If you are working with a backhoe, there are small buckets that make narrow trenches (so there is less soil to put back in place afterwards!). Finally, with a spade, there is no choice but to get the width of the tool.
Remove all the stones if possible.
In terms of depth, there are several opinions...
- I often advise 35 cm minimum (a little more than a spade).
- It is useless to dig at 60cm to protect yourself from frost. In some regions, if the winter is very hard, the ground can freeze very deeply. It is better to foresee anti-freeze systems as soon as the installation is done.
- The idea of putting the pipes at 90 cm to be sure that nothing freezes is very risky: the sprinklers are on the surface, and they will be damaged by the cold: it is therefore better to have the possibility of draining the whole installation. Moreover, at this depth, when it is necessary to intervene to modify or repair, it is very complicated. Think about the hole that will have to be made for a simple connection to be added.
Don't forget when opening the trenches to foresee the location for the manholes (see manhole picture).
2/ Setting up the pipe network
Unroll the polyethylene pipe at the bottom. In case of important presence of stones or pebbles, put a bed of sand under the pipes (in this case, dig deeper).
Install fittings and sprinklers.
DO NOT PLUG UP!
At the end of the line, do not put the plugs in yet. You must first send water into the pipes to clean them of all the debris that could have slipped inside. (see photo turbine380)
Screw in the plugs once this step is completed. Shim and adjust your sprinklers. Leave the system running and check ALL the connections.
There are no leaks after your installation? You can now fill in the gaps...a little...
3/ Locate the water network
3) If you have a 40 cm deep trench, put 20 cm of earth and then put a blue wire mesh. This will avoid piercing the pipes if you have to work on them in a few years: it will indicate the presence of pipes underneath. The blue color of this plastic mesh is important, it is a recognized standard for water (for information, green = telephone, red = electricity, yellow = gas).
4/ End of the earthwork
That's it, you can fill it in completely. Let the soil settle for several days before renovating the damaged lawn.
Technically, the trenches are not the most difficult part, but a well done earthwork allows an easy maintenance during the following years.
