negative dry vent pitch

[kimball gray]

In the attic, the kitchen, laundry and two bathrooms share the one vent that penetrates to the roof. One section of this vent sags and pitches downward for about 10 feet before going vertical and up through the roof. Is this allowed? Can moisture from rain or condensation essentially plug this vent at the low spot rendering the one vent useless? It appears that the ABS 40 piping just does not have the proper support and has sagged.

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[John Kogel]

I don't know about 'allowed' but it is certainly incorrect. Easy enough to fix. If the sag is less than a couple of inches, the vent will work. Put it in the report, but don't expect anyone to fix it anytime soon.

I think the rule for pipe support is every 4 feet, but somebody correct me if they know better.

That looks like the kind of tin roof you would see on a barn. No wonder there is only one plumbing vent. Vent flashings in that roofing are hard to impossible to seal.

[Brandon Whitmore]

Pipe support requirements vary by size of the pipe-- it should be easy to pull up for whatever code you use.

The DWV system must be sloped to drain.

[Greg Booth]

............just to note, that appears to be Schedule 40 PVC pipe-not ABS..........Greg

[Scottpat]

In the attic, the kitchen, laundry and two bathrooms share the one vent that penetrates to the roof. One section of this vent sags and pitches downward for about 10 feet before going vertical and up through the roof. Is this allowed? Can moisture from rain or condensation essentially plug this vent at the low spot rendering the one vent useless? It appears that the ABS 40 piping just does not have the proper support and has sagged.

Click to Enlarge

49.37?KB

Not good... Condensation and rainwater will collect in the low spot and clog the vent.... Simple fix that needs to be done.

[kimball gray]

Sorry, yes it is sched 40 not abs. dont know what I was typing. The roof is steel panel original construction built in 09. That is common in this area. I appreciate your replies and you did confirm my opinion.