myServer6 can coordinate the dumping of your RV Grey and Black and Fresh tanks. The IPRelays driver is used to electrically control the motorized dump valves.  The myTankDump app manages to coordination of the dump of multiple tanks.

On the dump valves, would be installed Barker motorized valves that install over the popular Valterra blade valves to motorize the valve movement.  Additionally the Barker system will energize for 3 seconds only which is slighly longer than it should take for the valves to completely close or open.  This helps protect the Barker motor from trying to move a seized valve blade.

The system is wired with a manual switch that is typically mounted in the water bay.  It is Open when not connected to a sewer drain.  When the RV is connected to a sewer, the switch is Closed.  This protects against inadvertent discharges.

You can also use a solenoid valve connected to the fresh water drain to empty the fresh water tank.  You can also install another solenoid on the fresh water fill line to automatically fill the tank when city water is connected.

To operate:

Ensure the system is booted.

Ensure the sewer drain is connected to a sewer.

Click the Drain button.  This should first drain the Black water tank.  The "Black Water Max" value is how many seconds max the valve should remain open to completely drain.  After this timer, the Black water valve is shut and the Grey water valve will then open for the "Grey Water Max" time..