UPC 705: Joints and Connections in Drainage Piping

Section 705 gives a set of rules for each DWV pipe material. Each material has its own subsection with its own approved joints. The headings the code uses read like this:

705.1 ABS and ABS Co-Extruded Plastic Pipe and Joints 705.2 Cast-Iron Pipe and Joints 705.6 PVC and PVC Co-Extruded Plastic Pipe and Joining Methods

The list goes on to cover copper DWV, stainless steel, and vitrified clay pipe and joints. Each subsection says how that material is joined and what is not allowed.

Plastic drain pipe is the most common in homes. ABS and PVC pipe are joined with a solvent weld. The plumber cleans the pipe, applies the right primer and cement, and pushes the fitting on. The cement softens both surfaces so they fuse into one piece. ABS and PVC use different cements and are not the same material.

Cast-iron drain pipe uses two main joints. Older bell-and-spigot pipe was packed with oakum and lead. Modern cast iron uses a no-hub coupling, a rubber sleeve held by a stainless steel band and clamps. See what a no-hub coupling is. Copper DWV pipe is joined by soldering. Each material has its own listed fittings.

Different materials often meet, such as new plastic tying into old cast iron. The code requires an approved transition fitting made for that pair, not just glue or tape. Some joints are flat-out banned in drainage. The code does not allow homemade or makeshift connections that can leak or catch waste. The point is simple. Use the listed joint for the listed material, and skip anything not approved.

If you see a drain joint wrapped in tape, sealed with caulk, or fudged with the wrong cement, it is likely not to code and likely to leak. A proper joint is why a licensed plumber uses the right primer, cement, coupling, or fitting for each pipe. For how these joints are checked on new work, see new construction plumbing permits in Phoenix. To learn how old drain pipe fails over time, see cast-iron drain pipe lifespan. Sound joints also make later leaks easier to trace: see how plumbers find hidden leaks. For related drain rules, see testing DWV piping and changes of direction.

UPC Section 705 is part of the Uniform Plumbing Code. IAPMO publishes it and holds the copyright, so only the section headings are shown here. The joint methods for each material are described in plain terms, not quoted. Phoenix enforces the 2024 UPC with local amendments. Read the section on the UPC viewer at UpCodes, review the official code at IAPMO, or confirm local amendments with the City of Phoenix Planning & Development Department at phoenix.gov/pdd.