CTE & TRADES · GRADES 9-12, CTE · 45-55 MIN
The Plumbing Wall: Wet Walls, Supply & Drain Runs lesson plan
Students locate fixtures, identify wet walls, lay string for supply and drain runs, and price a far-corner remodel.
At a glance
Time: 45-55 min
Grades: Grades 9-12, CTE
Subject: CTE & trades: Wet Walls, Supply & Drain Runs
Grouping: Teams of 3.
Space: A house plan with a kitchen and at least one bathroom.
Teacher prep: 15 min printing + 40 min taping
Included: Teacher guide, student sheet, checks for understanding, exit ticket with answers
Open the printable lesson: teacher guide and student sheet →
Essential question
Why do the bathroom and the kitchen share a wall — and what does it cost when they don't?
What students learn and show
Learn: Grouping fixtures on shared wet walls shortens supply and drain runs and lowers cost.
Show: Measure and price runs and explain why a remote fixture costs more.
Objectives
Locate every plumbing fixture on the plan (sinks, toilets, tub/shower, washer)
Identify wet walls and explain why fixtures cluster on them
Trace and measure supply and drain runs from the water source
Estimate total pipe length and compare two layout options by cost
Before this lesson students should: Measuring; multiplication with money.
Materials and prep
The 1:1 print
Colored string or chalk lines (one color supply, one drain)
Tape measures
Fixture checklists and run worksheets
Painter's tape for the redesign round
Prep (about 15 min to print, 40 min to tape)
Mark the water service entry and main drain location.
Provide a per-foot pipe cost.
Two colors of string.
Space: A house plan with a kitchen and at least one bathroom.
Grouping: Teams of 3.
Ways to run it: Painter's tape on the floor; 1:1 printed floor plan
Lesson procedure
Teacher model: 'Bathroom and kitchen share this wall: one run serves both. 34 ft x $6 = $204 before fittings and labor.'
Guided practice: Teams find and flag wet walls together before running string.
Fixture hunt: teams find and check off every fixture on the plan — count them before you pipe them.
Find the wet walls: which walls have fixtures on both sides, or fixtures stacked near each other? Tape-flag every wet wall and say what it serves.
Run the lines: from the service entry, teams lay string for supply runs to each fixture group, then a second color for drains falling toward the main. Walk each run at a calm pace and measure it.
Price the pipe: total the measured runs × the per-foot cost. Which fixture was most expensive to reach, and why?
The bad remodel: tape a new bathroom on the far corner, as far from every wet wall as possible. Re-run and re-price its lines. Feel the money flow away.
Debrief: this is why bathrooms stack in two-story houses and why 'let's just move the sink' makes plumbers smile.
Checks for understanding
Ask: What makes a wall a wet wall? Look for: It carries plumbing serving fixtures on one or both sides.
Ask: A run measures 34 ft at $6/ft. Cost? Look for: $204, before fittings and labor.
Ask: Why did the far-corner bathroom cost more? Look for: It needs new supply and drain runs over a longer distance.
Exit ticket
A new sink is 18 ft from the nearest wet wall. Supply and drain both needed at $6/ft. Added pipe cost? Answer: 36 ft x $6 = $216.
Scoring: 2 points (setup, answer) plus 1 for explanation.
Common misconception
Students may think: Drains can run any direction like supply lines.
Address it: Drains rely on gravity and need slope and venting; supply lines are pressurized.
Supports and extensions
Learning support: Fixture hunt with a picture checklist; the string-layer role is concrete and paired; provide one pre-traced run as a model.
Multilingual learners: 'Supply,' 'drain,' and 'wet wall' taught at the wall with the string in hand; the cost table carries the comparison in numbers.
Mobility and access: Runs can be measured with string on a tabletop plan; the reasoning stays the goal.
Extension: Add venting: every drain needs air. Where would the vent stacks rise, and which roof do they exit?
Transfer task: Find the wet walls on a second-floor plan above the first.
Spaced review: Next unit: compare two bathroom locations on a new plan by pipe length.
Standards connections
NCCER (framework)
Connections show which skills the activity practices. They are not a claim of full coverage; see the library for scope notes.
Why this approach
Drawing on 50 years of longitudinal data, spatial ability is an independent, underused predictor of STEM entry and achievement. Limit: Correlational. It shows spatial ability matters; it does not show that this lesson changes it.
Ready to teach it?
The printable version has the full teacher guide, a student recording sheet, prep steps and an exit ticket. Open the printable lesson →
Need the floor plan itself? Get a 1:1 print quote.
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