Mastering Wisconsin Plumbing
This podcast is dedicated to making the Wisconsin Plumbing Code (SPS 381–387) more accessible for plumbers, apprentices, inspectors, and designers.
Mastering Wisconsin Plumbing
Water Sizing Basics: From Bathroom Groups to Meter Limits
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In this episode of Mastering Wisconsin Plumbing, Ryan returns after a short break to talk about water sizing in a typical Wisconsin home. He shares updates on balancing college, the prefab shop, an upcoming trip to the MCAA Prefab Conference, and even a siding project at home. With day school starting back up, Ryan reflects on the value of applied learning and offers tips for apprentices connecting classroom code to field applications.
The technical focus dives into fixture supply sizing under SPS 382.40, explaining why ½-inch pipe is so limited, how meter size and maximum velocity requirements play into system design, and why a bathroom group always pushes you to a ¾-inch cold water line. Using both official code language and plain-speak interpretation, Ryan breaks down the “why” behind the rules and ties them back to real-world plumbing practice.
Listeners will leave with a clearer understanding of water supply sizing, code compliance, and how to think through system design in the field.
Sources Referenced
- Wisconsin Administrative Code SPS 381.01(29) – Definition of Bathroom Group
- Wisconsin Administrative Code SPS 382.40(8)(f) – Minimum sizes for ½-inch water distribution piping
- Wisconsin Administrative Code SPS 382.40 Tables – Fixture unit values, friction loss, and sizing by developed length
- Wisconsin Administrative Code SPS 382.40(7)(c) – Maximum velocity design requirement (8 feet per second)
