My Bus heater story

[pipes]

One more thing it will do..........Bottom flap DOWN upper flap UP it will suck the air from inside the bus and discharge the air overboard via the ABS pipe... No pic of that.
                           I am thinking of putting a 12 volt 3 inch RV sewer valve on the outer end of ABS pipe being it's not reachable from inside....It goes thru the floor behind the front bumpers.....Ken 

[pipes]

Update... The drivers and overboard air now have RV dump valves on them, no caps needed.

                                      Looks like this project generated as much feedback as my other invention,

Which is..........An electronic devise to clean out bird chit from cuckoo clocks