Posted 2/8/2019 20:31 (#7307551 - in reply to #7306699) Subject: RE: Water heater vent
I'm not an expert by any means but, I think the horizontal run as well as the shortness of the discharge outside is causing the problem.
I believe you need a power vent heater for horizontal discharge.....or you have to get that flu up where draft can be consistent.
Also, consider how close you furnace is to the water heater. Could be that the furnace fan is pulling /sucking in outside air through that vent.
Adding: Left as is, I think your counting on the gas value working properly to save your life when that pilot goes out.