Locker room drains clog because the code lets hair and soap residue through the shower strainer, and heavy use keeps feeding the same branch. The 2024 plumbing code sets only minimums: 1 1/2 inch outlets and strainer openings of at least 1/4 inch. A recurring clog usually means the trap or branch needs cleaning, not another quick snake.
What does the plumbing code say about shower drains?
Less than most people expect. Section 421.3 of the 2024 International Plumbing Code (IPC), as adopted in Phoenix, says "Waste outlets serving showers shall be not less than 1 1/2 inches (38 mm) in diameter and, for other than waste outlets in bathtubs, shall have removable strainers not less than 3 inches (76 mm) in diameter with strainer openings not less than 1/4 inch (6.4 mm) in least dimension."
Read that carefully. The openings must be at least a quarter inch across. That is a minimum, not a filter. Anything smaller than the opening, including a lot of hair, passes through, then collects in the trap and the pipe behind it. The strainer stops big debris and nothing else.
Locker rooms often add floor drains. Section 413.2 says "Floor drains shall have removable strainers" and that the drain "shall be constructed so that the drain is capable of being cleaned," with "Ready access" to the drain inlet. Section 413.3 sets a drain outlet of not less than 2 inches in diameter.
Phoenix's published amendments to the 2024 IPC (Ordinance G-7397) change other sections, including 604.4 and 704.1 for specific cases, but they do not list 413 or 421, so the base text applies there. Other Valley cities use their own adopted editions, so check the one where the gym is.
Why do the same drains clog over and over?
Four things stack up.
- Volume. A busy locker room can run many showers through one branch during a peak, and every one carries hair and soap film into the same pipe.
- A strainer that only catches the big stuff. As above, the code opening is generous. Hair and sediment get past it. The manufacturer of a hair and lint interceptor says its unit "intercepts hair and sediment which is commonly encountered in these areas," and it names dormitories, motels and beauty salons as typical places for it. A locker room is another place where hair and sediment head for the drain.
- Dry traps. A trap must hold a liquid seal of 2 to 4 inches under IPC 1002.4, and Section 1002.4.1 says "trap seals subject to evaporation" must be protected by one of its listed methods, such as a trap primer. A floor drain that is rarely wet, like one in an equipment area, can dry out and let sewer smell into the room. That is a separate problem from clogging, and our page on dry floor drains in Arizona covers it.
- Slope and shape. The code calls for horizontal drainage piping installed "in uniform alignment at uniform slopes." A sag or belly in the branch collects hair and soap even with a clear strainer.
What actually fixes it?
Match the fix to where the clog sits.
- 1Clean the strainer and the trap first. If the drain is slow and the strainer is clean, pull the trap or the access and look.
- 2Add a hair catcher at the drain, if the design allows it, and make it removable so staff can empty it daily. A solids interceptor like the Jay R. Smith unit is built to be emptied by pulling the cleanout plug and the basket. Whether one is needed is a design question for the plan reviewer or plumber, not a code mandate; see whether a salon needs a hair interceptor for how Phoenix treats hair interceptors generally.
- 3Clean the branch, not just the opening. If the same drain clogs again within weeks, the build-up is in the pipe. Hydro jetting scours the walls instead of poking a hole. See what hydro jetting is.
- 4Camera the line. A camera shows a belly, an offset or a broken joint that cleaning will not cure. What a commercial sewer camera inspection finds explains the report.
- 5Set a schedule. Gym lines earn a regular cleaning interval from their own history; see how often a commercial building should have drains cleaned.
What should a gym manager do between visits?
Keep a daily routine for the parts staff can reach. Empty hair catchers, clear strainers, and flush floor drains that are rarely used. Log which drain slowed down and when, since repeat locations point to a pipe problem. If water backs up from a floor drain instead of draining slowly, treat it as a line problem, and read why a floor drain backs up.
HQ Plumbing & Air jets and cameras commercial drain lines and floor drains, with upfront pricing and free estimates, and handles commercial drain cleaning for facilities that need the whole branch cleaned.