A distinct sewer gas smell was coming from the bathroom sink area. At first I wondered if there were a leaky pipe or such. Sniffing around, it was clearly strongest under the vanity. I discovered the Studor® Mini Vent Air Admittance Valve had gone bad, allowing sewer gases to back flow into the house.
Studor Mini Vent
The Studor Vent is a one-way air admittance valve that allows air to flow into the drain pipe but not out into the room. Running water going down the drain pipe creates a vacuum that could siphon the U-trap dry. The purpose of the U-trap (also called a P-trap or J-trap) is to create a water seal to prevent sewer gasses from coming back up the sink drain. The Studor Vent allows air into the pipe to break the vacuum preserving the water seal in the U-trap.
The Studor vent is commonly installed under the sink at least 4″ inches above the weir of the trap in situations where connecting to a vent pipe to the roof is not practical. A quick inventory of my house found a Studor Mini Vent is installed at nearly every bathroom sink and the kitchen sink.
Malfunctioning Sink Plumbing Vent
This vent is about 8 years old and malfunctioned because flies and mosquitoes (yuck!) from the sewer line had clogged up the valve, preventing it from fully closing to seal out the sewer gases.
Install the New Sewer Vent
A new Plumb Pak Studor Mini Vent was purchased from at Lowes for about $23.00. The old vent was removed with a pair of Channel Lock Pliers because the threads were tight due to the hardened plumbers putty on the pipe threads. Be sure grasp the main pipe firmly to minimize torquing the glue joints when unscrewing the old vent. A fresh swab of plumbers putty was applied to the threads and the new vent screwed on. Total time for the job was about 5 minutes.
Studor Mini Vent installation instructions are available on the manufacturer’s web site here.
Additional Studor Mini Vent installation photos are available here about 1/2 down the page.
Hope this saves you some money.
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