[PERLS]

Howdy All--

Whenever there's a serious storm with 40-50Mph wind velocities around my house, the standing water in one toilet bowl disappears.

Under ordinary conditions, all the drain fixtures function perfectly-- that is, the sinks drain in a flash. None of them gurgle or make unexpected noises. The toilets flush perfectly.

None of the traps are affected by flushing the toilets or draining the sinks.

But when gale force winds come in from certain directions one toilet bowl loses it's standing water. The water isn't blown out, it's sucked away as if a vacuum forms in the sewer line.

The toilet that empties is a "US goverment" toilet-- i.e. 1.6gal flush toilet, "low boy" type unit.

The other toilet in the house is non-goverment mandate flush. During these wind storm conditions it isn't affected although the standing water jumps around a little, but never clears.

There are two vent pipes that exit the two storey roof. Both pipes are 2" diameter below the roof, and exit as 3" pipes at the roof line. Vent pipes extend about 24" above the roof surface.

Main house DWV system is 4" PVC, with the "government toilet" on a 3" pipe branch that's about 6 feet long. This 3" pipe branch is vented by a 2" vent pipe that's 21 feet long straight up and exits at the roof.

My guess is that when the wind gusts hard enough across the vent pipe opening it causes a low pressure to build in the vent pipe. Column of air in vent pipe then acts as a piston that creates a short vacuum burst in the house drain system. Low flush government toilet has shallow trap that's finicky to slight pressure changes in DWV line. Negative pressure causes trap to drain.

Under "ordinary" condtions and wind velocities, no-effect on standing water in either toilet bowl.

Thoughts anyone? Fix for this?


THANK YOU for your attention!

[speedball1]

This situation doesn't happen very oiften but when it does installing a vent cap,(see image) helps to break up the airflow from around the vent pipe.
Good luck, Tom

[PERLS]

Howdy speedball1-

Thanks for your answer to my question about the DWV vacuum problem.

Can you elaborate a bit on the vent cap?

Can you provide me with a brand name or trade name? I did a bit of searching
And I find products meant for RVs rather than residential plumbing applications.

Many thanks!

Perls

[ballengerb1]

You are experiencing the Bernoli Effect in action. Even during moderate winds you will see the water bounce a bit in most toilets. In your situation it sucks water down the path of lease resistance. I will leave the brands to Tom but you can buy them at Home Depot.

[speedball1]

You may check out vent caps at: Plumbing Vents Good luck, Tom