Trailers In Niagra Ontario Dual Propane Tanks On Fleetwood Niagra Tent Trailer?

Dual Propane tanks on Fleetwood Niagra tent Trailer? - trailers in niagra ontario

Can we leave the two gas cylinders open at the same time to allow a continuous flow of propane in a tank empty ... or if we wait until they dry, turn it off and open the reserve tank, others?
Question on the basis of a reservoir dry during the cold night ... Freezing awoke heating did not work. Thanks