What does a plan checker look for on ADU plumbing sheets?

A plan checker reads the plumbing sheets to confirm that water supply, drainage, venting and water heating are sized and laid out to the California Plumbing Code, and that the drawings give the inspector enough to verify in the field. City correction sheets show the pattern: fixture counts and pipe sizing, a clear drain and vent layout, water heater details, and the connections to water and sewer service.

Items that appear on real correction lists

The Los Angeles Department of Building and Safety's plumbing plan check correction sheet and Yorba Linda's residential plan check list are good examples. Items they ask for include:

• Sheet basics. LA's sheet asks for the job address and scope of work on the plans, a scale no smaller than 1/8 inch per foot, and the license number and signature of an architect, contractor or engineer on every sheet.
• Fixtures. Yorba Linda asks for the location, flow rate and type of each proposed fixture and the new connection to the existing building drain or sewer.
• Water supply sizing. LA asks for a table of fixture units with hot and cold values, and riser diagrams showing pipe sizes, the fixture unit count on each leg, pressure regulators, backflow devices and the water meter.
• Pressure. A pressure regulating valve where needed to keep pressure at fixtures at 80 psi or less.
• Water heater. Type, size and capacity, the first-hour rating with the number of bathrooms and bedrooms, temperature and pressure relief discharge to an approved location, and a thermal expansion tank.
• Drain, waste and vent. The slope of horizontal drainage piping, vent sizing, and details for island fixtures and wet venting.
• Site plan. Yorba Linda asks for the water service line and meter size and location, the sewer lateral size and connection, and the locations of sewer, water, gas and electrical meters.
• Materials and notes. Pipe materials, and notes such as listed materials and fixture flow limits.

Local rules change the list

Correction lists reflect local ordinances and procedures. LA's sheet includes a note that new buildings must be all-electric with no gas piping, under a city ordinance, and it is used in the city's mechanical plan check section; how a small ADU is routed for review depends on the department. Yorba Linda requires a plumbing calculation worksheet at intake when a project increases the fixture count. Your city's list may be shorter, longer or organized differently.

How to use this before you submit

1. Ask your building department for its residential correction list or submittal checklist.
2. Compare it item by item against your plumbing sheets.
3. Confirm the site plan shows where the ADU's water and sewer connect.

What this means for your MEP plans

A plumbing sheet that answers these questions up front leaves less for the reviewer to ask. MEP Plans USA's plumbing sheets cover water supply sizing, DWV routing, the fixture schedule, water heater details and the sewer connection, and city plan-check corrections are included if the reviewer wants more. See what plumbing plans include, fixture unit counts and the DWV system. Every city's list differs, so confirm with your building department.

Sources: dbs.lacity.gov, yorbalindaca.gov.