Abstract: A fluid controller for a fluid supply system such as the plumbing supply system for a bathroom comprises hot and cold fluid temperature sensors and flow sensors which are installed in respective ones of the hot and cold fluid supply pipes upstream of the fluid discharge outlet. Hot and cold fluid flow control valves operated by valve motors are also installed in such pipes. The sensors and motors are connected to a microprocessor including a comparator means which is operative to compare values programmed in a memory means with signals received from the sensors so as to generate control signals for the motors so as to obtain a desired fluid temperature and flow rate at the discharge outlet. The controller can be installed in an existing plumbing system without disturbing the existing faucets and manual control valves. Alternatively, the controller can be used in a new installation with or without manual control valves.