Ceiling staining but no water leak

[Brian Harwood]

On a recent inspection in central Florida, I observed staining on the textured ceiling around the gas hot water vent as it entered the ceiling. This type of staining is consistent with what I have seen with a roof leak. The staining is very uniform around the vent entrance to the ceiling and protrudes approximately six inches out. When I inspected the attic side of the ceiling expecting to see a leak around the roof penetration of the vent, there were no indications of moisture or staining. This attic space is over the garage and is not insulated. Could this staining be caused by condenstion buildup during the colder months when the garage side of the ceiling is warm from the vent and the attic side cold (the home owner has the water heater at the highest setting)? Sorry I could not upload the photos due to excessive file size. Any thoughts?

[Billy Stephens]

On a recent inspection in central Florida, I observed staining on the textured ceiling around the gas hot water vent as it entered the ceiling. This type of staining is consistent with what I have seen with a roof leak. The staining is very uniform around the vent entrance to the ceiling and protrudes approximately six inches out. When I inspected the attic side of the ceiling expecting to see a leak around the roof penetration of the vent, there were no indications of moisture or staining. This attic space is over the garage and is not insulated. Could this staining be caused by condenstion buildup during the colder months when the garage side of the ceiling is warm from the vent and the attic side cold (the home owner has the water heater at the highest setting)? Sorry I could not upload the photos due to excessive file size. Any thoughts?
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Brian,

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[Kristi Silber]

I would think it more likely due to condensation on the vent itself, say in the late evening when temps outside drop but the attic is still warm, and people have gone to bed so there's enough time between hot water heating cycles for the vent to cool.

Photos would be good!

[Jack Feldmann]

What makes you think its not just running down the vent stack? Gap in flashing?

[Jerry Peck]

How 'tight' is the ceiling to the vent?

Single wall or double wall Type B gas vent?

[Thomas McKay]

Brian, I have seen the same thing on the ceiling penetration where copper pipes are used to attach a solar roof panel to a hot water tank, its definitely condensation resulting from the differences in temp. Its a good idea to check the roof penetrations to be sure there aren't any other contributing factors.

[Eric Barker]

I'm careful with water stains. I try to stick with what I know. If I see no other indicators of a possible cause I simply write that the stain exists and that the cause was not determined. It usually seems best to leave the assumptions up to someone else. Just because there is a stain does not mean that there is a water or moisture issue.

[Jerry Peck]

I'm careful with water stains. I try to stick with what I know. If I see no other indicators of a possible cause I simply write that the stain exists and that the cause was not determined. It usually seems best to leave the assumptions up to someone else. Just because there is a stain does not mean that there is a water or moisture issue.

Precisely why I asked the questions I asked.

To me, we don't "know" that it is a "water" stain.

The stain could be caused by heat ... depending on the answers to the questions I asked.

[Brian Harwood]

Jerry and Jack,

The sheetrock is approximately 1/2" from the single wall type B gas vent. My thinking is more along the lines of what Kristi mentioned in that as the attic temp drops in the evening, condensation forms on the vent pipe, and falls down past the ceiling sheetrock onto the ceiling plate. The ceiling plate extends approximately 3" out from the vent thus allowing contact with the ceiling sheetrock on the garage side. The sheetrock then absorbs the condensation causing the staining. But it may be better to stick with what Eric said and stay with what you know... since there were no active signs of moisture during the inspection.

[Rod Butler]

Jerry and Jack,

The sheetrock is approximately 1/2" from the single wall type B gas vent. My thinking is more along the lines of what Kristi mentioned in that as the attic temp drops in the evening, condensation forms on the vent pipe, and falls down past the ceiling sheetrock onto the ceiling plate. The ceiling plate extends approximately 3" out from the vent thus allowing contact with the ceiling sheetrock on the garage side. The sheetrock then absorbs the condensation causing the staining. But it may be better to stick with what Eric said and stay with what you know... since there were no active signs of moisture during the inspection.

I sort of agree with this, but it would seem to me that it is the vent pipe that has cooled as a result of the indoor temp being lower than the attic and does not matter the temperature of the attic, rather the attic humidity level.

[Jerry Peck]

The sheetrock is approximately 1/2" from the single wall type B gas vent.

The minimum required clearance is 1" all the way around.

If there is a 1/2" gap and there is condensation on the vent, wouldn't the condensation just run down along the vent and not even touch the drywall ceiling? Or is there a firestop collar installed which is collecting the condensation?

Just trying to visualize what is actually there.

[Brian Harwood]

Jerry,

From the information gathered here, the firestop collar appears to be collecting the condensation (or some form of moisture... it does not appear to be coming from the roof penetration) and providing the source of moisture which is then absorbed by the ceiling drywall.

Thanks to everyone for their input!