Liquid delivery system

A system for delivering a metered flow of liquid, said system comprising:

• a tank containing a supply of the liquid;
• a positive displacement pump, said pump being operable to withdraw the liquid from said tank via a suction conduit and to deliver a pressurized flow of the liquid via a delivery conduit;
• a metering orifice in said delivery conduit, said metering orifice being sized to modulate the flow of the liquid through said delivery conduit;
• a valve located in said delivery conduit between said pump and said metering orifice, said valve being normally closed, being opened in response to a pressure of the liquid exceeding a threshold level, and being operative when open to deliver the liquid to said metering orifice at a substantially constant pressure;
• a bypass conduit communicating with said tank and with said delivery conduit at a location between said pump and said first valve, said bypass conduit being configured and arranged to return a continuous flow of said liquid from said pump to said tank to constantly agitate the contents of said tank and to prevent overpressurization of system components downstream of said pump during operation of said pump;
• and
• a flow restrictor in said bypass conduit, said flow restrictor serving to modulate a return flow of the liquid from said delivery conduit to said tank.