A cross-connection valve, with upstream and downstream valving, which prevents backflow from contaminating the source of liquid is provided with field serviceability features by arranging the upstream valving and backflow discharge passageway means on an access door that normally serves as part of the valve body. A tool is arranged to enter through the discharge passage to hold the upstream valving in assembled condition on the access door, to permit field servicing for repair or replacement of the upstream valving, when the access door is open, and the downstream valving is also accessible for field servicing through the opening for the access door.