The new style plunger valves also have a vacuum breaker device built in. It is designed to let air into the suction side of the pump (making it loose prime) if the intake gets restricted. This is a safety feature to prevent entrapment. They also let the hoses hang straight down. There is a close up picture of the "B-adapter" and a plunger valve in this thread.

http://www.poolforum.com/pf2/showthr...ter-changeover.

Pappy