Hi Kreeper:
Stops are
shutoffs to each individual fixture. All sinks and toilets have shutoffs. Some tub/shower valves also have shutoffs.
The idea here is to shut off each shutoff individually until you find which fixture/valve is causing the cross connection.
If, for example, you shut the hot water shutoff off to the kitchen sink and then you run the cold water at the bathroom sink and you no longer have hot water coming out the cold side of the sink faucet then you will know that the kitchen sink mixing valve is defective and the cartridge will need to be replaced.
This test only applies to SINGLE HANDLE faucets/valves so no need to shut off shutoffs at two handle faucets...O.K.??
If your tub/shower valves cannot be isolated then test all other single handle valves/faucets and see what happens. If no answer the answer will be at the mixing valve of the tub/shower valves OR some other cross connection in the home.
Let us know what you discover...
MARK