I was cleaning gutters and thought I would stick a hose down the vents on the roof. Theres the main, which is 3 or 4" and a 2" one for a kitchen.

I could let the hose run for 5 minutes on the large one, no water backing up.

The smaller one quickly filled with water. I got my higher pressure nozzle and it quickly cleared. At that point I could run water for the same 5 minutes without backup.

So obviously I cleared an obstruction.

But my questions...

Is it necessary to do this periodically? Any harm in this?

also

How long would it take for a say 15' piece of 2" pipe to fill? In otherwords, can I be confident after the amount of time I let the water run that I no longer have an obstruction?

The only time you would see anything from the roof is if the obstruction was above any other vent connection, and it would have to be a nearly complete blockage or you won't see anything at all.

15' of 2" pipe holds almost 10 gallons of water. The rate of water from your hose depends on the pressure and hose diameter and length.

100' of 3/4" hose @ 70psi for 5 minutes.

@60 psi that's 22 gallons per minute I think....

however, my high pressure nozzle likely skunks up the whole equation...

heres one for paranoia....


say the pipe (galvanized) was clogged. Me shooting water down when it overfilled caused pressure enough to break the wall of the pipe.... shooting water inside the attic or wall.

After I was able to flow water down the thing for 5 minutes, do you think I would have seen that water inside the house by now?

After 5 minutes, it might be 50-75 gallons, so I think it would have appeared.

I have seen water leak from a drain from the 2nd floor to the crawlspace. A galvanized to cast 1.5" line corroded away at the main stack and it ran straight down the pipe chase.

thanks. It bothered me enough to get in the attic and check for moisture. I shimmied myself practically into the soffits! No moisture that I see.

However, I got a better look at the pipe. Its actually 1.5 galvanized. It drops from the roof penetration about a foot and then has a street 90 connected to another 90 before going vertical inside a wall. It looks to be impossible to fit a saw in there to cut off the 90.

Does that sound pretty bad to you?

Street 90 into 90 is probably proned to clog correct?

On a roof vent? Only if a squirrel is helping you out. It is more likely to corrode shut if you can keep debris out.

rain water alone is enough to corrode it closed? Its been in service I say almost 60 years.... do you think that's the issue why it was clogged? (I didn't visually see any leaves, seeds or debris of course).

The exterior of the fittings looked excellent.... no burrs, barnacles or deep rust spots.

Seeing that the street90/90 configuration is quite an obstruction for a snake, is it risky to be poking at the inside of those old galvanized fittings with a manual snake? Is poking a hole in the thing a real possibility?



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