I live an older house with an upgraded high efficiency furnace and new mid efficiency hot water heater (3 years old). I've noticed a number of times when I've entered our utility room that the hot water heater is backdrafting and sending the exhaust into the utility room instead of up the chimney. Slightly concerning. The small exhaust pipe from the hot water heater enters the original large exhaust that was previously for the furnace. Without the heat and air movement from the furnace there seems to be insufficient draft to pull the exhaust out of the atmospherically vented water heater.
I added a CO detector in the room and it has not gone off yet but it's easy to tell when you enter the room that it's not venting. When this happens I open the back door of my house which almost immediately helps with the differential and sends the exhaust up the pipe.
With that being said, what is the best and easiest way to fix this? New power vented hot water heater? Chimney liner? Power vent retrofit? Fresh air vent into utility room?
Any recommendations?