connector 48 and through substantially vertically oriented portion 42 with particular reference to fig4 arrows u201c c u201d depict the entrance of dilution air through an opening in the lowermost portion of substantially vertically oriented portion 42 that lowermost opening is preferably less than about 18 inches from ground level dilution air flows upwardly through substantially vertically oriented portion 42 through connector 48 and into blower 50 for combination with exhaust gases exiting from the terminus of flue 22 it can be seen especially as shown in fig3 and 4 that simultaneous intake combustion air and dilution air can occur from different locations and without intermixing this can be achieved by the seal between combustion air pipe 40 and dilution air pipe 42 this simultaneous flow reduces the chances of undesirable flammable ignition of vapors that might be located adjacent the water heater and provides for a means to lower the temperature of exhaust gases to increase flexibility of installation of the water heater typical gasoline spills or other flammable vapors tend to migrate near the floor and be drawn into the dilution air intake and exhaust harmlessly outside with the products from combustion due to the difference in magnitude of the volume of the separate air paths 20 combustion air 80 dilution air drawn into each conduit it is less likely that vapor concentrations will exceed the lower flammability limit at the combustion air inlet this invention thereby reduces the propensity for flammable vapors to enter the combustion chamber where they could be ignited and can evacuate the flammable vapors from the space during operation thereby reducing the potential that these vapors will build up and come in contact with another potential ignition source the size of the.