Not every reticulation system in Perth has a master valve and that’s not such a good thing.
Here’s why it matters:
The master valve exists essentially to prevent you from losing water if any of your station solenoids leak. It is screwed directly onto the dual check valve / cut in tap.
Each time you run your reticulation you are actually opening 2 solenoid valves – the master AND the station valve. Should you develop a leak in your solenoid at station 1 (for example) then it will not leak continually so long as your MV is functioning.
Occasionally people ring me and tell me that their retic is leaking continually and they can’t locate the cause. The first thing I check is whether there is a master valve installed. The easiest way to check this is to go to the control box and see whether there is a wire in MV/Pump terminal. If there is then you do have a master valve. If not then you don’t.
A lot of older houses bypassed this part and while its not critical it does protect you against unnecessary water loss. It is possible to retrofit a master valve and might even be quite easy depending on the location of your ball valve for isolating your retic (usually by your water meter)
Essentially what would need to be done is
a) locate the cut in tap
b) install the MV onto it
c) wire it back to the control box