Toilet Pipe Size and Diameter
If you plan on plumbing a toilet yourself, it helps to know what size pipe you need. There are different types of pipes used to install a toilet, including the drain pipe, closet bend and water supply lines. Learn the common sizes and diameters to better prepare for this big job.
Toilet pipe sizes are generally standardized for residential plumbing installations. For residential bathrooms, these toilet pipe sizes are the most common ones used. Most toilet installation parts are made to fit these pipe sizes.
Toilet Water Supply line – 1/2 inch copper pipe or plastic pipe routed from main water line or 1/2 inch cold water line.
Closet Bend – 4×3 closet bend connects to 3-inch schedule 40 pipe. This pipe installs underneath the toilet and connects directly to the toilet flange. Most flanges fit a 4×3 closet bend.
Toilet Drain Pipe – 3 inch PVC or 4 inch PVC pipe. Run from the other end of the closet bend to the home’s main drain line. Slope this pipe at 1/8 inch per foot grade to the main drain stack.
Main toilet drain or stack – 4 inch PVC or iron pipe. This is the home’s main drain line, the drain pipe connects to this pipe. Most homes use a 4-inch drain pipe, only high rises supporting more than 5oo appliances use a larger pipe size. Some homes may use a 3-inch stack. This pipe is typically an iron pipe.