An improved heat trap disposed in at least one of an inlet pipe and an outlet pipe for delivery of cold water into and hot water out of a water tank. The improved heat trap includes a tubular body and a seal element comprising first and second axially spaced flapper members which are adjoined by a spine. The seal element extends through the tubular body whereby the first and second flapper members form a seal against an interior surface of the tubular body to prevent the delivery of water through the tubular body.