Adhering to the International Plumbing Code (IPC) and Uniform Plumbing Code (UPC), a minimum of 2-inch drainpipe is required for any toilet. Although less common, this size must be installed in strict accordance with specific code sections to ensure proper ventilation and waste removal (Quora).
If it is an outlet size (from base of toilet to a Sewer Line, you need to replace all of the 2 inch line with the size of the toilet discharge (usually 3 inches). A 2 inch outlet on a toilet will clog the first time you use it. It is too small.
Toilet Vent Pipe Size? It's typically recommended that you go with a 2" PVC pipe for the vent. This is according to the uniform plumbing code (UPC).
A typical toilet waste pipe is 100mm/4 inches in diameter.
(a) Main Vent. The drain piping for each toilet shall be vented by a one and one-half inch (1 1/2") minimum diameter vent connected to the main drain by one of the following methods: (1) A one and one-half inch (1 1/2") diameter (min.)
The standard drain line size for a toilet is 3 inches in diameter, which is recommended to ensure proper drainage and prevent clogging. It's important to check local building codes for specific requirements, as they can vary by region.
A 2-inch (51 mm), 1½-inch or 1¼-inch (38 or 31.8 mm) drain would require a minimum 1¼-inch (31.8 mm) vent, this being the minimum size allowed.
Flush pipes are also manufactured to suit both of these sizes. Standard flush pipes are equal at both ends (1 1/2" to 1 1/2"), the European / modern size flush pipes are usually different sizes at both ends; 2" at the flush valve end which then reduces down to 1 1/2" at the toilet pan end.
Since these pipes shouldn't be carrying contaminated water (stop peeing in the sink when the toilet is occupied!), the waste system doesn't need to be vented the way a soil system does, as no harmful gasses are produced.
Standard Supply Line Sizes
3/8 inch: The most common size for toilet supply lines. 1/2 inch: Occasionally used, especially in older homes.
The Importance of Toilet Ventilation
The vents deliver fresh air into the system while removing gas and odors that are byproducts of the waste disposal process. It also helps to balance the pressure surge you create every time you flush the toilet.
A toilet trap sounds like something you'd want to steer clear of, but it's actually a key component of a toilet drain that helps keep sewer gases out of your home. There are two types of toilet traps—P-traps and S-traps—that accomplish the same goal with different designs.
The standard toilet drainpipe is 3 inches in diameter, though some toilets may use 4-inch pipes. Four-inch pipes are commonly used to carry wastewater out of the house and to the main drain line.
When builders look only at the table without reading the text, they find that a 2-inch-diameter drain can run a maximum distance of 8 feet to the vent.
Yes, It's Possible! In some plumbing setups, especially in older buildings or homes with limited space, a combined drain system might already exist. If the toilet and shower share the same drain, it's usually because of a “wet vent” arrangement.
Your toilet's individual vent needs to be 2”. (See UPC Section 904.1, Table 703.2, and Footnote 3 of Table 703.2). And if that's you, install a 3”x3”x2” wye, with a 2” street 45 to vent this toilet.
When connecting a toilet soil pipe, it is advised to never use a pipe smaller than 100mm to carry the waste from said toilets. This size soil pipe is not designed to handle solid waste and can result in a blockage. So 110mm soil pipe is important to consider in this instance.
When drain lines aren't properly vented, low pressure inside the pipe can suck water out of the traps, letting sewer gas in. Air pressure imbalances inside the drain pipe can restrict water flow and cause sluggish draining, often mimicking a partial clog inside the pipe.
PVC Pipes
Polyvinyl chloride pipes (PVC) are commonly used as part of a sink, toilet, or shower drain line. Its plastic tubing is ideal for this kind of usage because it protects the water from rust and corrosion better than other types of pipes. This capability also makes PVC pipe incredibly durable.
In general, the maximum distance of the toilet from the main drain should not exceed 4 meters, with a 2% minimum slope. Within these limits, the plumbing system can guarantee an effective draining, avoiding bad smells and the problem of emptying the siphons.
But do you know the proper slope? The ideal slope of any drain line is ¼ inch per foot of pipe. In other words, for every foot the pipe travels horizontally, it should be dropping ¼ inch vertically. Many drains either have too little slope or too much slope.
You need a 2" vent to take off from the branch line within 6 feet of the toilet. It can run up any convenient wall until it is above the toilet's flood level.
a 1.5 inch vent can run 20 feet in the horizontal. A 2″ vent can run 40 feet in the horizontal. However you can increase it by 1 pipe size over what is required and run indefinitely.
How to vent a toilet without going through the roof? The best way is to install an AAV which will pump air into your drainage system. Other methods are using the Garden Hose technique, a plumber's snake, or using baking soda and vinegar solution.