Fernco bottom outlet AAV kit installed on a 1.5 inch tubular drain under a bathroom sink, next to the P-trap
 
Coming November 2026
Air admittance valves

AAV Kits

Vent a sink without opening the wall. The kit clamps onto 1½″ tubular drain, lets air in while the sink drains, then closes to keep sewer gas out.

 
Inline and bottom outlet 1½″ tubular Up to 8 DFU (branch) No glue
 

Gurgling sink? It may need air.

Drains need air to drain. Without a vent, draining water can pull the water out of the trap. That’s what lets sewer gas into the room. An air admittance valve lets air in when the drain needs it and stays closed the rest of the time.

Lets air inOpens when the sink drains to help keep water in the trap
Fernco Inline AAV Kit: gray air admittance valve clamped on a black rubber tee with stainless steel clamps
Code heightThe inline kit sets the valve 4″ above the branch drain
Keeps gas outCloses so sewer gas stays in the pipe
No wall work

Vent under the cabinet. Where your local code allows an AAV, you can vent a sink without running a new vent pipe through the wall or roof.

Fernco Inline AAV Kit installed on the trap arm under a bathroom sink
8 DFU

Rated for up to 8 drainage fixture units on a branch.

Clamps on

Stainless steel bands and a screwdriver or nut driver. No glue or cure time.

1½″ tubular

Both kits connect to 1½″ tubular drain pipe.

Tested

Designed to meet ASSE 1051, NSF/ANSI 24 and EN 12380.

Two kits. Which one fits?

Both do the same job. It comes down to where your drain goes.

Fernco AAVKIT-1 Inline AAV Kit
AAVKIT-1

Inline AAV Kit

For a trap arm that runs into the wall. The tee goes in the horizontal trap arm and holds the valve 4″ above it.

  • 1½″ tubular to 1½″ tubular
  • Bathroom, kitchen and bar sinks
Fernco AAVKIT-2 90 degree Bottom Outlet AAV Kit
AAVKIT-2

90° Bottom Outlet AAV Kit

For a drain that comes up from the floor. The trap arm connects at the side and the drain continues out the bottom.

  • 1½″ tubular to 1½″ tubular
  • Kitchen islands, vanities and laundry sinks

How an AAV works

A light seal inside the valve moves with the air pressure in the drain.

Cutaway of an air admittance valve with the seal lifted and air flowing in through the vents and down the pipe
Water drainsDraining water pulls on the pipe. The seal lifts and air comes in, so the trap keeps its water.
Cutaway of an air admittance valve with pressure pushing up from the pipe and the seal pressed closed
Pressure pushes backWhen the pipe pushes air up, the seal closes. Sewer gas stays in the drain.
Cutaway of an air admittance valve at rest with the seal closed
At restWith no water moving, the seal sits closed on its own weight.

See it installed

Watch an AAV kit go in under the sink.

Four steps

Inline kit

  1. Marking a 1.5 inch section of the trap arm under a sinkCut out 1½″Pick the install location and remove a 1½″ section of drain tubing.
  2. Fernco inline AAV tee fitted into the trap armFit the teeInsert both pipe ends into the tee sockets and push in until they stop.
  3. Tightening the clamp on the inline AAV tee with a screwdriverTightenHand tighten all bands with a flathead screwdriver or 5/16″ nut driver.
  4. Running water in the sink to check the inline AAV kit for leaksTestRun the sink and check for leaks.

Bottom outlet kit

  1. Cutting 1.5 inch tubular pipe with a pipe cutterCut the tubingPick the install location and remove a section of drain tubing.
  2. Fernco bottom outlet AAV fitting on the drain with the trap arm at the sideFit the teeInsert both pipe ends into the tee sockets and push in until they stop.
  3. Tightening the side clamp on the bottom outlet AAV kit with a screwdriverTightenHand tighten all bands with a flathead screwdriver or 5/16″ nut driver.
  4. Running water in the sink to check the bottom outlet AAV kit for leaksTestRun the sink and check for leaks.

Tools: tape measure, flathead screwdriver or 5/16″ nut driver, pipe cutter or hacksaw, deburring tool or sandpaper, and a bucket or towel for the water in the trap.

Install within 15° of vertical, where air can get to the valve and you can reach it later. Check your local plumbing code before you install.

Where it fits

Each kit handles up to 8 DFU on a branch. Typical fixture loads:

FixtureTypical DFU
Bathroom lavatory1
Bar or prep sink1 to 2
Kitchen sink2
Laundry or utility sink2

Typical DFU values are based on the International Plumbing Code (IPC) Section 709. Your local code has the final say.

Specifications

PartsAAVKIT-1 Inline AAV Kit
AAVKIT-2 90° Bottom Outlet AAV Kit
Connects1½″ tubular to 1½″ tubular
CapacityUp to 8 DFU (branch), where permitted by code
StandardsValve designed to meet ASSE 1051, NSF/ANSI 24 and EN 12380
GasketElastomeric PVC, tested to ASTM D5926
Clamps300 series stainless steel worm gear
Temperature-4°F to 140°F
UseResidential drain, waste and vent only
Weight0.8 lb
PackagingCarded polybag

Common questions

Is an AAV allowed where I live?

Many plumbing codes allow air admittance valves, but rules vary by state and city. Check with your local plumbing inspector before you install.

Does it replace the vent on my roof?

No. An AAV vents a fixture or branch. Most codes still require at least one vent to open air for the building’s drain system.

Which kit do I need?

If the trap arm goes into the wall, use the AAVKIT-1 Inline kit. If the drain comes up from the floor, like on most kitchen islands, use the AAVKIT-2 Bottom Outlet kit.

Will it fit Schedule 40 pipe?

The kits are made for 1½″ tubular drain pipe, the thin-wall pipe used under sinks. Not sure what you have? Reach out.

Where should the valve sit?

Within 15° of vertical, where air can get in and you can reach it for inspection or replacement. Don’t install it inside a closed wall without an access panel. The inline kit sets the valve 4″ above the branch drain for you.

Will it fix a slow drain?

Only if the problem is missing air. An AAV won’t clear a clog. If the drain is blocked, clear it first.

What temperatures can it handle?

-4°F to 140°F.

Under the sink

Connect to the drain.

Fernco Drain & Trap Connectors join the tubular pipe under the sink to the 1½″ or 2″ drain line in the wall or floor.

  • 1¼″ or 1½″ tubular to drain pipe
  • No glue or primer
  • Made in USA
See Drain & Trap Connectors ›
Fernco drain and trap connector installed under a sink