How Loop Vents Work | This is the magic of a time-tested plumbing loop vent for island sinks. Don’t take the shortcut using an AAV. Copyright 2022 Tim Carter

How Loop Vents Work - Forget About AAVs

Have you heard the old saying, “You don’t know what you don’t know.” I think it’s an overarching axiom with just about everything there is to know about building homes. Stop and think for a moment about all you don’t know about all of the things hidden behind your plaster or drywall walls and ceilings not the least of which is your entire plumbing drain and vent system.

I’ve been a master plumber since 1981 and it’s one of the trades I love the most. I find it attractive because when installing plumbing drain and vent pipes in a new home it’s a true three-dimensional puzzle. If you have a young family member looking for a rewarding career where she/he will always be in demand, suggest plumbing. It’s a marvelous way to meet homeowners who will thank you for fixing their pipes.

My guess is the first thing you don’t know is the true purpose of the plumbing vent pipe that pokes up through your roof. Most homeowners I talk with compare it to their chimney. A chimney is designed to expel smoke or combustion gas out of a house. Thus, you might think the plumbing vent pipe’s job is to spew stinky sewer gas outdoors.

Roof Vent Pipe Lets Air In not Out

The exact opposite is true. The purpose of the vent pipe is to let air into the plumbing system just like that tiny pinprick hole you put into a large jug of drinking water that has a spigot in it. If you’ve ever tried to use one of those jugs without poking the hole in it, you discover rapidly the water in the jug has a very hard time getting out.

Before I share with you the way kitchen island sinks have been vented for decades, allow me to indulge you with the movement of water and air in the pipes hidden behind your walls and ceilings.

Imagine no one’s home or you’re sleeping. Let’s also imagine you don’t have any dripping faucets that waste vast amounts of water. When no water is running the only water in the plumbing pipes is that you have in the traps under fixtures and perhaps some condensate water in the vent pipes. The rest of the volume of all the pipes is filled with air and sewer gas.

What Happens When Toilets Are Flushed

When you flush a toilet, 1.6 gallons of water rushes through the toilet bowl into the pipes below the toilet. As the water cascades down the vertical pipes it pushes the air in the pipes ahead of it. This air must be replaced and it comes into the system via that stubby pipe sticking up through your roof. This same scenario happens when you put water down any other drain pipe in your home. It’s precisely why each plumbing fixture in your home needs to have a vent pipe as part of the drain.

If you go to my www.AsktheBuilder.com website you can watch my How to Vent Plumbing video. What you’ll see are all sorts of vent pipes that go up walls behind your bathroom vanities, your kitchen sink that’s on a wall, and all your other fixtures.

But how can you do this if you have a sink in the middle of a kitchen? Who wants some ugly plastic pipe going up through the countertop up to the ceiling? No one! Wait, I know what you’re about to say, “Tim, isn’t that what air admittance valves (AAVs) are for?” Yes, these devices that have moving parts were invented to try to solve the problem. The issue is I constantly have people pay me to tell them why they have sewer gas smell in their kitchens. It happens when the moving parts in the AAVs fail.

For all the decades before AAVs, plumbers like me installed a humble loop vent inside the island sink cabinet. It’s an ingenious, elegant, and simple solution that has no moving parts and is guaranteed to work for the life of your home. The best part is it takes maybe just an extra 30 minutes to install a loop vent.

First and foremost, the entire loop vent system including the drain pipe must be constructed using 2-inch pipe. This is paramount because it’s vital the horizontal portion of the drain pipe never fill completely with water. There has to be a layer of air above the water that’s traveling down the pipe on its way to the sewer or septic tank. The short horizontal pipe draining your kitchen sink needs to be a smaller 1.5 inch pipe to restrict the amount of water entering the loop vent.

The loop vent system looks like the giant letter P resting on its side. To top part of the P is where the kitchen sink pipe connects. The lower leg of the P is the vent part of the system. Here’s the magic of how it works.

I show you how to create a perfect loop vent in this wonderful product.

Imagine you fill your kitchen sink to the brim with water. You then pull out the stopper and the water begins to rush into the short 1.5-inch pipe. This pipe fills completely with water until the sink drains. As the water drops down into the vertical 2-inch pipe it’s swirling and there’s more than enough volume to allow air into the pipe as well as the water. Remember, before the stopper was pulled there was nothing but air in the plumbing system including the entire length of drain pipe from your sink to the sewer or septic tank.

When the water hits the horizontal part of the loop vent heading towards the sewer, it starts to level out with perhaps a 1/2-inch air space on top of the rushing water. As the water heads towards the sewer, the air on top of the water is rushing over it the other direction going up the other vertical pipe that’s part of the loop vent. It’s replacing the air that used to be in the pipe. It’s that simple and the best part is it will be trouble-free for the life of your home!

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Sewer Gas Detector | This is a p-trap although it’s a different design. This device, so long as it’s filled with water, stops sewer gas and vermin from entering your home. Copyright 2022 Tim Carter

Sewer Gas Detector - Read the Short Sewer Gas EBook First

Do you have the same problem I have with the passage of time? It’s hard to believe, but I’ve been a master plumber since 1981. I’ve always loved doing plumbing work because it’s a true three-dimensional puzzle.

You may not realize it but just after the US Civil War smart people finally connected disease and sickness to bacteria. All of a sudden it became quite apparent that it was a great idea to pipe body waste to remote parts of cities instead of throwing pans of it out second-story windows to splash on the street.

Plumbers all of a sudden became as respected as physicians because their skills working with pipes allowed people to stay healthy. This was true of both drain lines and the installation of potable water lines that provided fresh, clean, and sanitary water to millions of people.

To this day these facts are a primary driver why plumbers are well-paid. If you have a daughter, son, or grandchild that wants to have a rewarding career that provides significant income, point them to a trade school that teaches this craft.

It’s vital that plumbing drain pipes, as well as the vents that connect to them, be installed correctly so sewer gas never enters your home. Each week I solve sewer gas problems over the phone with homeowners just like you. In fact, yesterday I solved a vexing problem for a New Mexico homeowner just hours before he was expecting house guests.

Sewer gas can be found in septic tanks, city sewers, and the drain pipes in your home. It smells horrible. It’s caused by the decomposition of bodily waste and rotting food that you send down your drain pipes. It’s toxic and can cause severe illness if you’re exposed to enough of it for long periods of time.

Just two years ago a man hired me to come to his home to solve a sewer gas issue. His wife was seriously ill and no doctor could figure out the cause. Within minutes I connected her suffering to the leaking sewer gas. I found out that they had installed a new tile floor on top of an existing one in a powder room immediately adjacent to where his wife sat and watched TV.

After the new floor was installed, the tile setter or plumber didn’t put in an extra wax ring to account for the fact that the toilet now sat 1/2-inch higher than it did before the new floor was installed. Invisible sewer gas was leaking from the base of the toilet like smoke issuing from a raging wood-burning fireplace. As soon as two wax rings were installed on top of each other on the toilet flange and the toilet reset, the sewer gas stopped entering the home.

A year ago I decided to help homeowners like you solve sewer gas problems on your own. I decided to write a simple short book about sewer gas. It explains how your plumbing system works. I then ask you a series of questions that helps you narrow down why you’re having sewer gas issues. Within a few minutes you can normally figure it out on your own. If not, I can call you on the phone as I do with many many people each year.

Here are the basic things you need to know about your plumbing system and sewer gas. First, it’s vital the plumbing pipes in your home work like the blood vessels in your body. When all is well in your body, your blood stays inside the blood vessels. If you cut yourself or a vessel breaks under pressure, blood leaks out. The same is true for the pipes in your home. When all is well, the liquids, solids and sewer gas stay in the pipes.

But if a pipe cracks, has a hole drilled in it, or a trap under a fixture dries out, then sewer gas and vermin can enter your home. Dried-out p-traps under sinks, showers, and floor drains are the most common source of sewer gas.

Two years ago I did a phone consult with a man that owned a condo in a high-rise building in Monaco. He had a horrible sewer gas problem. It turns out the source of the leaking gas was in multiple other condo units above and below his unit!

Many of the condo owners only stay in their units for a few months out of a year and while they’re gone water evaporates from the traps under all the fixtures and from the toilet bowls. Once the water seal in the traps is broken, the sewer gas wafts into the unit and then enters the tall plumbing shaft where all the pipes go down to the street. The sewer gas in the tall shaft was getting into the man’s condo.

I had him contact the condo maintenance manager. He used his master key and went into each vacant condo. He then ran water in all the fixtures and flushed all the toilets. Within hours the sewer gas problem in the entire high-rise building stopped.

Wind can also cause a problem. That plumbing pipe up on your roof works the exact opposite of chimneys at factories. Chimneys are designed to get rid of smoke from a fire or furnace. Plumbing vent pipes do the opposite. They supply fresh air down into the pipes in your home each time you run water in a sink, shower, or flush a toilet.

If you want to read the first chapters of my short sewer gas book for FREE, go here.

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