Not knowing your floor plan I'm going to guess. I'll use mine as an example.
rear dump on mine is one pull for black and one pull for gray. The front dump is one pull for Galley and one pull for Gray. Each tank has a seperate dump valve. No tank has 2 dump valves.
Not all tanks have automatic change over valves. If it is automatic The regulator handle points to the tank in service. Both tanks must be on but it will only draw for the tank at a time. Mine regulator has a valve with a pointer but is not automatic. I leave on off so I know when the in service one empty's. I then switch the valve to the other tank and remove the empty.
Regulator with a directional handle only draw from one tank at a time weather automatic or not.
2011 Keystone Sprinter 323BHS. Retired Master Electrician. Retired Building Inspector.
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