Yellow! Have comparatively modern house (built 1975) in Eastern Cape, South Africa. Non-pressure geyser always develops air lock after 3 minutes running bath. Outlet pipe is slightly upward orientated -which looks wrong- could this be the cause? Major PT to then eliminate resultant airlock. Placing copper T with vacuum breaker at highest point of outlet pipe did not solve problem (B. idiot, who would have thought it might save me?) Desperately seeking answers from kind experienced person(s)!