High Efficiency furnace vent pipe, why can't both pipes point down?

[WobblyElvis]

My son's house uses a large gas water heater for both hot water and hydronic heat in winter. Last week we had a couple hours of extremely heavy rain. The water heater failed to light the next day and water was leaking from the bottom of the heater. Eventually it was found that rain had entered the water heater via one of the vent pipes and after the water was removed, the water heater would light up and function properly.

Question is.... every time I see one of these high efficiency systems, the pvc [assume gas rated] pipes leaving the building have one pipe with an elbow pointed down and the other is just horizontal. Why can't they both point down, ensuring less change of water intrusion? Is it against code?

 

[Rmay635703]

At the very least should have a drain on the one pipe.

My guess is they want to minimize cross flow but spacing them far apart would solve that

 

[CDX825]

You don't want them both down because the intake will pull in the exhaust gasses. The intake should be pointed down. The exhaust side should go straight out. The exhaust side should have no problems with water getting in it because if its vented through pvc its a condensing unit anyway and will create lots of water vapor in the exhaust.

 

[tbm5690]

The downward one is intake, the horizontal is exhaust. My best guess as to why the exhaust can't point down is condensation freezing and plugging it during the winter months. Additionally, any rain getting in should just drain down through the condensate drain to the floor and not plug anything up.

 

[WobblyElvis]

My best guess as to why the exhaust can't point down is condensation freezing and plugging it during the winter months.

This appears to be the best reason.

 

[Wrenchturner44]

When I had a high efficiency furnace installed, I explained to the contractor that I did not want "the vent snorkels" installed on the side of my house. He finished the installation using a vent cover like this one. I have never had an issue with rain or snow.

 

[dnewton3]

Solution ...

Get a 45 deg elbow and point the exhaust bent "down" 45 deg, and also "turn" it 45 deg away from the intake.

Also, it helps to turn the two ports 90 deg apart from each other.