Here is an illustrated example of a solenoid valve assembly in a manhole. This one, as well as those that could follow, is only an example among many solutions or preferences that each installer may have. Nevertheless, some basic principles are stated.
1/ Mounting the manifold
Here two solenoid valves with the water inlet in the center. Although there is a main water cut-off, a shut-off valve is always placed at the manhole inlet. The solenoid valves are removable before and after, by the "removable union" type fittings. The solenoid valves have been disassembled so as not to bother with the wires, protective tape (orange here) prevents the intrusion of earth. Pipe primers allow the manifold to be mounted completely without worrying about the rest of the piping.
2/ Positioning the collector
After the hole has been made for the manhole (wider than necessary), the bottom is laid flat, the solenoid valve manifold is placed, as well as a sheath here to allow the cable to be passed later. The pipes under the manifold allow to raise it a little with respect to the level of the manhole (the usefulness of this will be seen later).
3/ Arrival of the manhole
The manhole has been cut with a hole saw in order to let the pipes pass. It is positioned over the collector. We check that it is level and aligned with the limits of the garden (wall, alley, ...). Note that the manhole is deliberately larger than necessary: it is a false economy to try to put a maximum number of valves in a small manhole; maintenance and repairs are difficult, the connections are not accessible, ...
4/ Wedge the manhole
Once the manhole is correctly in place, we start to backfill all around it, gently so as not to shift it. The geotextile film is pulled up along the outside walls so that the soil does not enter the manhole.
5/ Backfilling
Once the manhole is in place, it can be completely filled in. The pipe primers are useful on some sites where the manholes are installed well before the garden pipes.
6/ Manhole bottom
The bottom of the manhole is filled with pebbles. The pieces of pipe which supported the collector are removed.
7/ Cleaning
The manhole is cleaned with water. All the components of a collector are watertight, so it can be washed with water. The solenoids are screwed -by hand- on the solenoid valves, the wires will not interfere anymore. The multi-core cable coming from the programmer is brought into the manhole, longer than necessary (it will not be cut).
8/ Connections
All that remains is to connect the wires of the solenoids with the cable, using waterproof connections. Here, the connections are enclosed in a box, for cleanliness reasons, so as not to leave unsightly connections lying around: be careful, it is never the box that makes the watertightness, but the specific connections used.
