Your bathroom plumbing system is not complete without installing a vent. Follow this detailed step-by-step guide to properly vent your toilet, sink, or shower.
Why Should You Vent Your Toilet, Sink, and Shower?
When you flush your toilet or drain your sink and/or bathtub, wastewater from these plumbing fixtures rushes through their individual drain pipes into the main drain pipe.
As the wastewater heads into the main drain pipe, it’ll push forward the air present in the drain pipes. If this air doesn’t escape, it’ll slightly compress to form a resistance. This will affect the free flow of the wastewater, leading to water lock in the drain pipes.
Also, if additional air doesn’t enter into the main drain pipe, a vacuum effect can form within the pipe and this will slow down the flow of wastewater. Hence, it’s important to have a vent for the entry and exit of air when necessary.
Furthermore, you need the consider the following to vent a toilet, sink, or shower:
- Drain works on a gravity-flow system. So, drain pipes should be sloped downwards at ⅛ to ¼ inch drop per foot.
- The size of your drain pipe should be 3 inches minimum.
- The “horizontal” vent pipe(s) should be sloped slightly upwards to allow condensation to run back to the drainpipe(s).
- Except if your shower or sink is sitting too far away, a single vertical vent stack running through to the roof is enough.
- According to the IPC (international plumbing code) standard, the individual vents should be sized at 1.5 inches. According to the UPC (uniform plumbing code) standard, the individual vent should be sized at 2 inches. But you may choose to plumb your toilet with a 3-inch vent.
In either case, a vent pipe shouldn’t be less than 1.5 inches.
- The toilet, sink, or shower must have a trap and the trap arm (the pipe between the trap and the vent) should be 6 feet minimum.
- The rule of thumb is that other plumbing fixtures aside from the toilet can work with 1.5 inches fittings.
Step-by-Step Guide on How to Vent a Toilet, Sink, Or Shower
There are several different options to vent a toilet, sink, or shower – indirect connection, parallel, or opposite side. Your best option depends on the factors available in your bathroom. However, the most common configuration is the parallel setup as presented in the picture below.
You can also choose to either follow the IPC standard or the UPC standard of venting your toilet, sink, or shower.
According to the parallel setup above, a 2-inch PVC pipe (vent stack) is placed within (or along) the wall behind the toilet, reaching the roof. Other vent pipes run parallel to the vent stack. Also, the vent pipes are connected parallel to the main drain.
The vent stack connects to the toilet’s drain pipe. The shower’s drain pipe and sink’s drain pipe are vented with 2 inches and 1.5 inches pipes that branch from the 2 inches PVC pipe.
So, let’s get started.
Step 1: Connect the Toilet’s Drain Pipe
In this plumbing setup, the vent stack connects to the toilet’s drain pipe. So, setting up this plumbing system starts from the toilet flange.
Connect the toilet flange to a 4-inch toilet drain pipe. At the elbow, reduce the drain pipe to a 3-inch pipe using a 4-in. by 3-in. DWV closet bend. The reduction in pipe size allows the free flow of wastewater.
Step 2: Run the Trap Arm into the Vent Pipe
Where the elbow is reduced to 3 inches, connect the trap arm to run horizontally from the toilet flange. As said above, you may choose to observe the IPC standard or UPC standard.
Whichever standard you wish to follow, the trap arm should be at least 6 feet long. Connect the end of the trap arm to a 3-inch combo. Try as much as possible to adhere to this requirement during installation, or else you may be forced to remodel your toilet when the authorities get to know it.
Since toilets already have an in-built trap, you don’t need to install a trap again when connecting the pipes. Trapping the toilet again is called “double trapping” and is a code violation because it’ll cause unnecessary obstructions in the wastewater flow.
Step 3: Run the Vent Pipe
The 3-inch combo should connect upwards to the vent pipe that brings in air from the stack vent. As seen in the layout above, a sanitary tee connector is attached to the vent pipe at an ideal distance to connect horizontally to the vent pipe from the shower.
Connect another pipe vertically to the sanitary tee connector. At an ideal distance, connect another sanitary tee connector to link horizontally to the vent pipe from the sink.
Connect a pipe to the vertical opening on the sanitary tee connector. This vertical vent runs upward above the roof as the roof stack.
Step 4: Run the Main Drain Pipe
From step 2, connect the 3-inch combo to the DWV pipe that connects to a 3in by 3-inch by 3-inch wye at an ideal distance. Glue the 3-inch combo, DWV pipe, and 3in by 3-inch by 3in wye correctly to ensure that there is no clogging at the elbow.
Connect 3 inches pipes to both ends (discharge ends) of the 3-inch by 3-inch by 3-inch wye. This forms the main drain pipe. You will also connect the shower drain and sink drain at suitable distances along the main drain pipe. Considering the slope, one end of the main drain pipe should be closed with a clean-out adapter while the other end leads into the sewer tank.
Step 5: Connect the Shower Drain and Vent Pipe
According to the diagram, the shower is connected to the left-hand side.
Just like in step 1, connect a 2-inch p trap to the trap arm using a DWV closet bend. Connect the trap arm horizontally to a 3in by 2in sanitary tee connector. The 3-inch outlet connects to a DWV pipe that connects to a 3-inch by 3-inch by 3-inch wye at an ideal distance along the main drain pipe.
The 2-inch outlet connects with a 2-inch pipe that bends to connect to the sanitary tee on the vent pipe rising behind the toilet.
Step 6: Connect the Sink Drain and Vent Pipe
According to the diagram, the sink is connected to the right-hand side.
Similar to step 5, connect a 1.5-inch trap adapter to the trap arm. Connect the trap arm horizontally to a 1.5-inch sanitary tee connector. One outlet connects to a 1.5-inch pipe that connects to a 1.5-inch by 3-inch by 3-inch wye at a suitable ideal distance along the main drain pipe.
Connect one of the two 3-inch outlets on the wye to the main drain pipe. Seal the other 3-inch outlet with a 3-inch clean-out cap.
Connect the 1.5-inch vertical outlet on the sanitary tee to a 1.5-inch pipe that bends to connect to the sanitary tee on the vent pipe rising behind the toilet.
Make sure that you get all the fittings right, considering the gravity and gradient of your ground. Also, the arrangement of the toilet fixtures doesn’t matter i.e. the toilet doesn’t necessarily have to be installed in the middle of the sink and shower. The toilet can come before the sink and shower as seen in the image below.
Watch this video to better understand how to vent a toilet, sink, or shower
Installing a toilet, sink, and shower requires detailed knowledge of the arrangement of pipes. You must also consider the gravity and gradient of your ground when connecting these fixtures. To avoid code violations, double-trapping is highly discouraged.
If you find it difficult to connect these fixtures correctly, it might be best to hire a professional plumber for the job. Good luck!