Guide · Nov 4, 2026
How to Read Plumbing Plans: Fixtures, Drain and Vent Lines, Risers and Schedules
By Eli Gewirtzman, Owner · Last checked Nov 4, 2026
A plumbing set has two kinds of drawing. The plumbing floor plan shows where each fixture sits and how the pipes run horizontally. The riser (isometric) diagrams show the same piping in 3-D, with every pipe size, so you can see how it all connects. Read the legend, find each fixture tag in the fixture schedule, then trace the water supply in from the meter and the drain-waste-vent piping out to the sewer.
Plumbing sheets usually carry a P prefix, like P-101. Our guide to what sheet numbers like A-101 mean covers the numbering. On a small house, plumbing is sometimes shown on the floor plan itself, so check the sheet index first.
1. Start with the legend and the general notes
Plumbing drawings depend on line types, so the legend comes first. Most offices draw each system with its own line style or label: cold water, hot water, sanitary waste, vent, storm and gas. The general notes set pipe materials and often a default slope. King County, Washington, allows pipe slope to be “noted on each pipe segment or as a General or Keyed note on each sheet,” but it won’t accept a general note on the cover sheet alone. So check the notes on the sheet you’re reading.
2. Read the plumbing floor plan
The plumbing floor plan is the architectural floor plan with the walls drawn light and the piping drawn on top. Minnesota’s Department of Labor and Industry asks the floor plan to “show all fixture locations, all horizontal drainage pipe locations, and all pipe sizes for new plumbing.” Look for:
- Fixtures: toilets, sinks, tubs, showers, washers and floor drains, each with a tag like P-1 or WC-1 keyed to the fixture schedule.
- Pipe sizes: written beside each run, like 3″ or 1/2″.
- Cleanouts: often marked CO. Las Vegas asks for the “location and size of cleanouts to be shown.”
- Water heater: Las Vegas asks for its location, type and size.
Our blueprint abbreviations guide decodes the shorthand you’ll see on these sheets.
3. Tell supply piping from drain-waste-vent piping
| System | What it does | What to look for |
|---|---|---|
| Water supply (cold and hot) | Brings pressurized water in from the meter to each fixture | Smaller sizes, shutoff valves, backflow devices, the water heater |
| Drain-waste-vent (DWV) | Carries waste out by gravity and lets air into the system so traps don’t siphon | Larger sizes, slope arrows or notes, traps, cleanouts, vents through the roof |
| Storm | Carries roof and area drains | Roof drains and the roof area each one serves |
| Gas (if shown) | Feeds appliances | Pipe sizes, lengths and appliance loads |
Minnesota requires both “water riser diagrams” and “soil, waste and vent riser (DWV) diagrams,” which is a good reminder that they are separate systems drawn separately.
4. Read the riser and isometric diagrams
A riser diagram, usually drawn as an isometric, shows the piping as if you were looking at it from a corner of the building, so vertical pipes and horizontal runs both show up. Richmond, Virginia, asks for one “entire riser so the reviewer can determine how all piping interconnects,” not several partial risers. On the waste and vent riser it asks for “all pipe sizes” and “connected loads (DFU counts),” plus traps and cleanouts. DFU stands for drainage fixture units, a way of rating how much each fixture loads the drain. On the supply riser it asks for valves, pipe type, backflow devices and the water heater.
To read one, pick a fixture on the floor plan, find the same tag on the riser, and follow the pipe until it reaches the main. Every change in size should be labeled. When a riser continues onto another sheet, King County asks for “a clear and distinct label at each continuation,” so look for a matching label on the next sheet.
5. Check the fixture schedule
The fixture schedule is a table listing each tagged fixture with its description and its hot water, cold water, waste and vent connection sizes. Las Vegas allows fixture and fixture-group pipe sizes to be given in a fixture schedule instead of on the plan, and asks for a water supply fixture unit count with the required meter size. If a fixture tag on the plan isn’t in the schedule, or the sizes disagree with the riser, ask the designer before anyone orders material.
What permit reviewers look for on plumbing sheets
| Item | Minnesota DLI | Las Vegas, NV | Richmond, VA |
|---|---|---|---|
| Fixture locations on the floor plan | Yes | Fixture types with symbols | Not stated |
| Pipe sizes | All new plumbing | Water and DWV piping | Every pipe on the risers |
| Water supply riser | Isometric, all sizes and fixtures | Not stated | Isometric, valves and backflow |
| Waste and vent riser | Isometric, all sizes and fixtures | Not stated | Isometric, DFU counts, traps, cleanouts |
| Cleanouts | Not stated | Location and size | On the waste riser |
| Water heater | Not stated | Location, type and size | On the supply riser if new |
| Who may design | Licensed PE or licensed master plumber | Not stated | Not stated |
Your town’s list may differ. For how many paper copies a building department wants, see our plan copy requirements by state.
Printing plumbing sheets
Riser diagrams are full of small pipe-size labels, so print them at the size they were drawn at. A half-size print halves every label too. Most residential sets are drawn on 24×36; our 24×36 (ARCH D) blueprint printing guide covers that size. If the designer used color to separate hot, cold and waste lines, print those sheets in color so the legend still works.
PrintMyPlans.com prints PDF plans on 20 lb bond at $1.95 per sheet in black and white or $3.75 in color, the same price at every size: 17×22, 18×24, 22×34, 24×36, 30×42 and 36×48. Printing only, before shipping:
| Example | Sheets | Black & white | Color |
|---|---|---|---|
| Plumbing floor plan and riser sheet, 1 copy | 2 | $3.90 | $7.50 |
| 4-sheet plumbing set, 1 copy | 4 | $7.80 | $15.00 |
| 4-sheet plumbing set, 2 copies (permit and plumber) | 8 | $15.60 | $30.00 |
WELCOME20 takes 20% off a first order, so the 8-sheet black-and-white example comes to $12.48 in printing. Price your own set with the plan printing cost calculator. For trade and field sets, see construction plan printing, and for complete house sets, architectural plan printing.
We print plans; we don’t design, check or change them. Questions about pipe sizes or code items go to your designer or plumber.
FAQ
What is the difference between a plumbing plan and a riser diagram?
The plan is a top-down view showing where fixtures are and how pipes run across each floor. The riser diagram shows the same piping in 3-D with every size, so you can see how floors and fixtures connect.
What does DWV mean on plumbing plans?
Drain, waste and vent: the gravity piping that carries waste out of the building and the vent piping that lets air in.
What does CO mean on a plumbing plan?
Usually a cleanout, an access point for clearing the drain line. The legend confirms it.
What is a DFU?
A drainage fixture unit, a rating of how much load a fixture puts on the drain. Reviewers use DFU counts to check drain sizes.
Should plumbing plans be printed in color?
Only if the designer used color in the legend. Most plumbing sheets are drawn to read in black and white.
Printing it
When the PDF is final, upload it on the order page and choose the size it was drawn at, black and white or color, and the number of copies. Export native CAD files to PDF. Order by 3 PM ET, ships same day, arrives as soon as the next day, rolled in protective tubes, to all 50 states. Affordable 2-day air and next-day air shipping are there when you need them.
Sources
- Minnesota Department of Labor and Industry, Plumbing Plan Review Checklist (revised 7.1.2025)
- City of Las Vegas, NV, Building & Safety, Residential Submittal Requirements (1.9 Plumbing Plan Requirements)
- City of Richmond, VA, Planning & Development Review, Plumbing Plan Requirements (Sept 14, 2018)
- King County, WA, Public Health, Plumbing Plan Review Design Guidance (updated 11/21/25)
Order by 3 PM ET, ships same day. Delivery timing depends on the shipping service and destination. See the terms for business-day and holiday details.