I read an article on water heater backdraft here: http://structuretech1.com/2013/09/wa...rafting-signs/ which got me thinking so I checked mine out. When the burner is lit on the water heater, I don't have a draft (even though there is a cold air return in the basement near the water heater). My test is as indicated in the article but it seems more intuitive to me to light a lighter next to the draft hood and see if the flame pulls into the vent pipe or blows away from it / blows out.
When only the pilot is lit though I do have backdraft when the AC is running. How concerned should I be about this (In the short term). I've been in the house 3 years so it's been that way. CO detector in basement hasn't gone off but doesn't show PPM. I've ordered one that does.
Is the test only relevant with the water heater running?
My plan in the long term is to fix the return ducting that is too small from the furnace to the returns. (I'm guessing an installer / homeowner figured this out and cut in the basement return to compensate).
Sealing off the return in the basement should deal with any backdraft concerns but if I do it now I'm starving the AC for air. There are two vents in the basement that have been closed ever since I bought the house. If I open them, the backdraft with the pilot only improves but the basement is freezing and upstairs doesn't cool.