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Under sink vent not working |
![]() Oatey sure vent 6 DFU Approved to vent pipes up to 2" Buy sure-vent air admittance valve: 1 piece vent and tubular adapter 1 piece vent and tubular adapter |
![]() Oatey sure vent 20 DFU Approved to vent pipes up to 3" Buy sure-vent air admittance valve: Admittance valve 20 DFU vent Oatey sure vents are 100% closed if they fail... so never sewer gas odor |
![]() Sure vent wall box So vent can draw air Buy louvered access box: Oatey sure vent wall box Oatey access panels |
![]() Tubular drain pipe Flexible coupling 1-1/2 to 1-1/4 connector Chrome flexible drain pipe |
![]() T plus 2 with applicator brush Guarantee no leak Buy Rectorseal at Amazon |
Connect to tubular
sink drain Approved up to 2" drain pipe Resource: Oatey 6 DFU spec sheet |
Glue to 1-1/2" or
2" PVC Approved up to 3" drain pipe Resource: Oatey sure vent installation |
Louvered access required for inside-the-wall sure vent Sure vent requires open access to air; to draw air, and for visual inspection, and for replacement |
Hard-to-find tubular parts for sink drains | T plus 2 guarantees
no leaking under sink (read instructions below) Does not dry out in can. 1/4 pint: handy size for DIYers |
Question about vent not working: Under sink vent not working. I have double sink with 1 P trap and a Tee that connects both sink bowls. There is AAV vent installed between P-trap and where pipe enters wall. When I run my disposal, it blows air up out of the other bowl and I get septic smell. It only does it when disposal is running. What can I do to fix problem? |
Answer: The problem with AAVs
If the drain is not letting water flow as quickly as normal vented sink, it can eventually cause line to get blocked with garbage. The sink probably shouldn't be on an island, and maybe your experience will help others with similar remodeling plans. With a double sink, a single P trap is code, but there are other issues. First of all, the AAVs will respond to air pressure in the line. But they do not function like a normal through-the-roof-vent that also allows air to escape the drain line. If air is drawn into pipe (Negative pressure) the AAV lets air into the drain line ..... and drain works correctly. But when the drain is full of water and moving toward the AAV, it pushes a column of air in front of the water, creating positive pressure. The AAV shuts off when there is positive pressure..... The air has nowhere to go ... it cannot push up through an open vent to the roof and get released into atmosphere like normal ... instead the air creates blockage, causing a back up and gurgling into the other sink bowl. Once the column of water passes the AAV, it will begin draw air into the pipe from the AAV, and the water should be able to flow normally. Suggestions for island vent not working: - Experimenting with different behaviors might help. -If the drain line is not full of water, the AAV seems to work fine. -So maybe there is too much water being used when the disposal is running. Reduce the water flow. -Cut up less garbage and increase water flow. It will take longer each time, but long term result will probably be better. -To make sure all garbage is getting flushed completely out of the line, run water into the drain for a while after each use. Also consider following actions in this order: - Blockage: Take apart the tubular plumbing under sink to check if there is constriction. - Use drain cleaner and run water. - After repeated drain cleaner, fill both sinks several times and let drain to try and flush out line. Repeat each week. - Higher level of DUF for the AAV ... use 20 DUF instead of 6 DUF ... might help - Bigger diameter pipe. Larger 2" schedule 40 drain and trap up to the point where AAV is located ... this will increase pipe capacity ... then hopefully the drain line and AAV will give better result. - You don't say it the tubular drain lines are 1-1/2" slip joint typically found in residential construction .... or a larger size 2" schedule 40 PVC drain typically found in commercial installations. The commercial size drain is solvent welded (get one with a clean out) and probably should be a requirement for island installation and might solve problem. - Install 2" PVC trap and drain instead of using 1-1/2 tubular (likely available at plumbing supply) - If your kitchen has access from underneath, say from the basement or crawlspace etc, check if the drain line drops straight down into a 3" pipe ... getting the kitchen drain into a larger pipe as soon as possible will improve flow. Buy: 2" P trap |
![]() ![]() Vent stack on roof. Must meet code for distance above roofing material. 6" minimum. To use sure-vent and meet code, the home MUST have at least 1 main stack vent to roof I never met a plastic roof boot / roof jack that didn't leak at one point. Use lead ... it will last forever Buy: Lead roof boot Roof boots |
![]() Failed black vent will let sewer gas into home. Black vents are rated 1 DFU: rated for 1-bowl sink ... like a bar sink. Black vents are cheap and they fail in open position .... letting sewer gas into house. A new black vent at my home lasted 1 month. Previous black vents lasted 20 years since I moved in ....but I replaced them all with Oatey 6 and 20 DUF. FYI: Oatey vents have higher DUF ratings, last longer, and fail in closed position ... sewer gas will never enter home. The first failed black vent stuck open and let sewer smell into home. It took a week to figure out the odor was inside 2 rooms ... so I suspeced a broken drain line ... but after looking at vent lines in attic, I could see there were just two vent stacks and no branch lines that connected to other drains ... then I thought ah ha ... maybe the house has quick-vents or AAVs... but if true, then they were concealed inside the wall. A concealed AAV is against code, but better than a broken drain line under the slab. I estimated where the vent was located based on where p-trap entered the wall... figuring it was slightly higher. The space under cabinet was too small to work, so I cut through the opposite side in middle of bedroom wall. Wanting to keep the repair small, I started drilling a line of tiny holes through sheetrock, then used a piece of wire to probe and find vent. Locating top of vent was key, so I knew how high to cut. Then located each side of vent based on when the wire probe hit nothing. I was able to remove black vent with channel locks and screw on a 1-1/2" cap to seal the opening, making sure to use T2 thread sealant to guarantee it would never leak septic odor. Then the new Oatey vent was installed under sink for easy access later if needed ... no more concealed vents. I discovered 3 more black vents hidden inside walls, and replaced each with correct DUF rating. In the process, I discovered that two sinks had no vents, one of them the kitchen sink. The other was rarely used and close to main stack. I think the kitchen sink worked all those years because the house is on septic system and does not have garbage disposal, and the 1-1/2" tubular drain under sink drops down pretty quick into a 2" PVC drain line that is about 28' long, but apparently enters the main 3" drain line right where the main vent stack goes up through roof. The home has 2 main vent stacks, and I never paid much attention but always wondered why the drains gurgled when the back yard septic was flooded with rain water. I would just go outside and unscrew the clean out and problem would mostly disappear .... The 2 main stacks kept problem to a minimum, but over the years, the back pressure from using sinks with flooded septic field was causing unsanitary sewer gas to bubble into home. The problem continued on a couple sinks even after the Oatey vents were installed, because an AAV does not work under positive pressure of a bath draining when the 3" main drain is full of water. So my experience shows that AAVs will continue to have problems when septic system is flooded ... and that installing through-the-roof-vent-lines is best solution . We finally resolved the issue permanently a few years ago ... after installing new areobic septic system that treats water and then empties though a sprinkler system in back yard.... and have not experienced any gurgling because the main 3" drain line doesn't fill up with water when it rains. Buy from my affilate links: Admittance valve 20 DFU vent Resource: How to make perfect drywall repair |
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![]() Oatey sure vent 6 DFU/ Approved to drain pipes up to 2" All in one vent for under sink Buy: sure-vent air admittance valve: 1 piece vent and tubular adapter 1 piece vent and tubular adapter |
![]() Add sure-vent to P-trap P-trap goes through wall Oatey meets code requirement: Minimum 4" space between horizontal pipe and vent Oatey 3925 rated 6 DFU/ Oatey 6 DFU vent specification sheet Vent must be located at least 2 pipe diameters away from trap weir Buy: Oatey sure vent with tubular adapter Sure vent with tubular adapter Sure vents at Amazon Buy: other parts: ![]() P-traps and trap adapter S-traps Quick vent or sure-vent at Amazon 1-1/2 tubular drain pipe PVC slip joint Tees at Amazon PVC slip joint elbow T plus 2 thread sealant at Amazon 'Trap weir' is the final bend in trap as water exits trap Read more |
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Image shows 20 DFU Sure Vent
installed under bathroom sink. Image below shows 20 DUF approved up to 3" pipe Bathroom requires minimum 3 DFU 3 DFU is enough vent for toilet, sink, and tub/shower Kitchen sink requires minimum 1-1/2 - 2 DFU Washing machine 2 DFU This sink drains into a line that also drains bathtub. The 20 DFU is plenty of vent to prevent slow drainage, gurgling drains and prevent sewer gas from entering home. Buy: sure-vent air admittance valve: 1 piece vent and tubular adapter 1 piece vent and tubular adapter Resources: Oatey 6 DFU vent specification sheet DFU specification chart |
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