Residential Plumbing Code RequirementsResidential Plumbing Code Requirements

The International Residential Code provides code regulations for residential plumbing and sewer issues. These regulations determine how plumbing should be installed and maintained.

Code requirements for residential plumbing

The following are the code guidelines for certain procedures under residential plumbing:

Water supply systems

According to the plumbing code, underground water pipes must be placed at a depth of 12 inches, and any solder used for linking the pipes must be lead-free in water systems for drinkable water. The pipe supplying water to any building must be at least 3/4 inches thick, although the code recommends using supply pipes that are 1 inch wide. Outlets for hoses and landscape watering appliances that use the potable water-supply system must link via a backflow prevention device. The code suggests the use of screw-on vacuum breakers.

Change-of-direction fittings

The plumbing code recommends using 1/16 bends, 1/8, bends, 1/6 bends or other similar sweeps for alterations to the direction of the drainage pipe. Drainage pipes that empty into another drainage pipe should do it through a wye or combination wye connection, a connection fitting that enables sewer line access, typically with a sewer snake. The code exempts horizontal pipes that empty into vertical pipes from this requirement, but discharge must occur through a sanitary “Tee” connection.


The code demands accessible cleanouts at the top end of each drainage pipe, excluding horizontal branches that are shorter than 5 feet and do not attach to sinks and urinals, pipes at a slope of 18 feet or higher from the horizontal and pipes situated on or over the second story of the building. A cleanout must be present at every 100 feet and for every change in pipe direction that goes beyond 135 degrees. Cleanouts for underground pipes need to be stretched to grade.

Traps and venting

According to the code requirements, every plumbing fixture in and around the house must have a trap, and every trap must have a vent pipe shielding it. The traps help to stop sewer gas from backing up into the house, while the vents stop any water prevent in the traps from being transferred via water movement to another place in the drainage system. The code allows special venting for kitchen island fixtures in cases where it would be impractical to vent a fixture in an isolated location where vent fixtures are usually demanded in the universal plumbing codes.


The code requirements recommend that the residential sewer must start at least 2 feet away from the building and link to the public sewer, with at least 1/4 inch per foot slope. A different cleanout must be on the upper end of the sewer, along with a pop-up cap or back-pressure relief cap at the property line cleanout. The entire assembly must be created from cast iron, and the pipe must have a wideness of at least 4 inches. The code also requires a 3-foot maximum to the cleanout.

Final note

It is necessary to follow the code requirements when designing a residential plumbing system. A professional plumber has the knowledge to make a functional system that is up to code.

Get more information here: or call Bevills Plumbing, Heating & Air Conditioning at (325) 225-4115

Check out what others are saying about our services on Yelp: Read our Yelp reviews.