Water coming out of water heater power vent

[stevemachine]

So my brother in law has a direct vent Bradford white 50 gallon water heater. Every time it kicks on he is getting like a half gallon or more of water coming of his vent on the outside. I have never hear of this. It sounds like there is some sort of build up if pressure then, the water comes shooting out. Ill post pictures soon. Any thoughts or opinions?

 

[stevemachine]

Picture of vent inside, once its light outside ill post a pic outside

 

[Caduceus]

I'll give this one a shot, Steve.
I've seen some power vent HWTs get ice build-up from condensation in the vent pipe, but this usually results in the tank shutting down due to air flow restriction. If there is just enough ice to allow flow without affecting the air flow switch, the warm air could be thawing the ice and producing the sudden water discharge.
I would also have to guess that the inducer motor isn't strong enough to cause a sudden rush of water from pressure build-up, so the possibility exists that the pipe has back-fall towards the outlet exiting the house. Power vents should have slight fall (like drainage/vent pipes for plumbing) towards to tank. A "belly" or sag in the pipe may also be presenting an opportunity for water to build up and then freeze.
If this is a new problem and the tank has been in for years, changes in landscaping over the summer may be allowing cold air to enter the pipe when the tank is not in use. The absence of a 45 or 90 degree fitting with a screen could account for cold air turbulence in the pipe, too.
With all of these considered, taking a look down the pipe with a flashlight may reveal any other new obstructions that can develop ( i.e hornets nests, shrub leaves/nettles, dead critters) that are blocking the pipe and letting moisture build up.
Hope this helps.

 

[IFIXH20]

Caduceus, the vent piping should have a slight fall towards it's termination point and not the motor correct.
If i'm not mistaken bradford white makes a drain kit for the power vent water heater if you do not have one installed now.

 

[Caduceus]

http://www.statewaterheaters.com/lit/im/res-gas/184326-001.pdf
Note pages 17 and 18 of this PDF installation manual from State.
I can see where it would seem practical to have the slope go towards the outside of the house to allow drainage of condensation. But, especially in colder regions, condensation will freeze into a little icy waterfall on the outlet and block the flow of air. Also, most power vented HWTs and high efficiency furnaces allow for a vertical install of the vent. Both vertical and horizontal installs are designed to accommodate the free flow of rising hot air/carbon monoxide with assistance from the blower. Returning condensation will be heated, evaporated and discharged.
As always, though, consult the manufacturers installation manual for any changes in design that require an atypical installation.

 

[IFIXH20]

http://www.statewaterheaters.com/lit/im/res-gas/184326-001.pdf
Note pages 17 and 18 of this PDF installation manual from State.
I can see where it would seem practical to have the slope go towards the outside of the house to allow drainage of condensation. But, especially in colder regions, condensation will freeze into a little icy waterfall on the outlet and block the flow of air. Also, most power vented HWTs and high efficiency furnaces allow for a vertical install of the vent. Both vertical and horizontal installs are designed to accommodate the free flow of rising hot air/carbon monoxide with assistance from the blower. Returning condensation will be heated, evaporated and discharged.
As always, though, consult the manufacturers installation manual for any changes in design that require an atypical installation.

I knew this, that was a bonehead post I posted .

 

[stevemachine]

Thanks guys, ill take a closer look. Now basically they had these vents installed before with a tankless unit. Now they got that swapped with a tank due to multiple issues with it, so a majority of the venting was there previously and the issue didn't exist before but this all make sense and I think I have a pretty good understanding of some solutions. Thanks!