Came across this today during an inspection. Because of the height of the water heater the installed set the draft hood flush to the top of the water heater and added an opening for air (?) in the middle of the vent connector. It feels wrong, the manufacturer doesn’t cover it, why is it wrong please?
It is wrong because it does not comply with the manufacturer’s installation instructions for the listed appliance.
Yup I get that, I just was hoping someone understood the drafting stuff to explain why its wrong
Well…
Naturally drafted appliances bring cool air in through the draft diverter to cool the exhaust gas some and facilitate convection and protect the burner / flame from excessive drafting which can affect the flame. That’s why there is a draft diverter and a space below it. Take away the legs and you disable it.
90° bends are not permitted in natural draft appliances unless the listing indicates that they are.
Natural draft vents need to slope upward at least 1/4 inch/foot
The length of the run should not exceed the length of the rise for a natural draft appliance
The vent termination of a natural draft appliance must be a minimum of 5 feet above the appliance outlet…
You have to install it the way that manufacturer says too. You can’t cut the legs off of the draft diverter to shoe-horn it in where it doesn’t fit.
I have come across those same vent openings in the vent pipe a few times, checked for CO levels in the room the first time i saw this and no elevated levels. Seems insane how it cant be leaking some but i guess it’s a vent that helps with drafting out through the pipe. Just had another 2 days ago. I just state that drafting should be at the draft hood as recommended by mfg and have technician review the drafting of the unit and replace pipe opening if recommended by technician.
Yes I measured for CO also and got a zero reading the boiler has one of those open bottom elbows for draft right behind the unit. The water heater has been in place for 15 years.
Thanks Chuck - appreciate the concise information.
When a factory draft hood needs to be removed in order to achieve the minimum rise of the pipe needed, a horizontal draft hood should have been used rather than that barometric draft regulator and the factory draft hood should have been taken off completely to get more rise. *(Either that or a shorter water heater)
*The purpose of a draft hood is not to let cool air in, it is to allow back draft out, otherwise let’s say if wind was blowing flue gases back down and not getting out they would go down to the burner and smother the flame causing carbon monoxide.
Letting cool air in would be the opposite of trying to keep the flue gases hot which is what makes a flue work. (hot air rises)
Don’t think I’ve ever seen any flue pipe without elbows.
Not to code, not to manufacturer’s installation requirements, but that does not mean it isn’t going to work. The gas flame needs a good draft to burn properly. If the chimney is providing enough draft to provide the burners with the right amount of oxygen, the not to code stuff is not interfering with combustion.
The 0 CO reading, no scorching suggests that correct combustion is taking place, or nobody is using hot water 
You could never say that though.
It might be a wrong, I guess!