First you will need to install the main pipework from cage to cage, and from your water source (see below) and consider whether to include electric heating cables to prevent freezing in Winter (because these cannot be shortened or lengthened this is a permanent decision!). Because we get temperatures below -30 we have used two of these, one for normal freezing weather, and the second for extreme temperatures. We have put these INSIDE the water pipes, for maximum effect and least heat required. The pipe should run outside the cage to avoid damage by gnawing.
Then using tees the valves as shown in the diagram above are fitted to cages at a convenient height.
The water source can be a large enclosed container, for example a 5-gallon jerry can, pail with lid etc. or the mains water supply if there is one to your rabbitry. To reduce pressure in the pipes install a float valve (like the one in your toilet tank). This would also need a coil of heating cable in the tank during freezing weather.