In the Field · Part 4
Leak detection: slab leaks, acoustic and pressure methods, thermal imaging, and repipe vs. reroute
The leak call is the one where a plumber can destroy a house looking for a $200 repair, and the one where the method pays for itself fastest. This lesson is the sequence: the meter test that splits service line from house, the hot-side-versus-cold-side isolation that splits the house in two, the pressure test that finds the slow ones, the acoustic and thermal tools that put a mark on the slab, and the inspection hole that confirms before it destroys. It ends with the decision that follows a slab leak: repair the spot, reroute the line overhead, or repipe the house, each with its cost logic, its permit, and the honest statement of what the other two would have meant.
What the full lesson covers
- Meter test first: all fixtures off, indicator moving; house valve closed, indicator still moving means the service line, stopped means the house. Four minutes, no tools.
- Split the house: close the water heater's cold inlet; if the indicator stops, the leak is on the hot side. A warm spot on the floor, a water heater that runs, and a hot slab are the slab-leak signature.
- Pressure test each side with a gauge to find slow leaks, then listen (acoustic) and look (thermal) to locate; open the slab only where two methods agree.
- Repair the spot when the pipe is otherwise sound; reroute the line through the attic or walls when one line has failed in a house whose other lines are fine and the slab is expensive to open; repipe when the material or the pressure history says the next leak is coming.
- A leak search is time and materials with a stated estimate on the service and repair form; the repair or repipe is a home improvement contract with a permit. Over 80 psi static, the regulator goes on the ladder every time.
Unlock the full lesson
This is the public summary. The full lesson has the method, the worked cases, the checklists and the templates:
- All in-depth lessons, exam prep and After the License
- 1,000+ practice questions
- AI tutor (100 messages included)
- 14+ hours of audio lessons
- Full-length practice exams
- Pass guarantee
Start Free — Create Account$149 one-time · lifetime access · no subscription
Already have an account? Sign in
More lessons in The Field: Method, Code, and Cases
- 1The diagnostic method: verify, isolate, cheapest test first, cause not symptom, the options ladder, document
- 2Permits: when one is required, what is exempt, pulling it online, the inspection sequence, what inspectors look for, and handling corrections
- 3Daily-use code: drainage slope, venting, water sizing, cleanouts, trap arms, and fixture units, with the section for each
- 4Gas piping in practice: sizing, CSST bonding, the pressure test, appliance connectors and shutoffs, sediment traps, and seismic shutoff valves
- 5Water heaters I: tank. Seismic strapping, the T&P discharge line, expansion tanks, sediment traps, pans, venting, and the garage rules
- 6Water heaters II: tankless and heat pump. Gas sizing, venting, condensate, the 2025 Energy Code direction, and where the gas-ban ordinances stand
- 7Sewer and drain I: the camera, the locator, hydro-jetting vs. cabling, and when each is the right tool
- 8Sewer and drain II: trenchless vs. open trench, whose lateral it is (it varies by city), backwater valves, and point-of-sale lateral ordinances
- 9Case: the hissing line. The meter test, the supply leak that fed the roots, the lateral to the city tap, and the contract and permit trail
- 10Leak detection: slab leaks, acoustic and pressure methods, thermal imaging, and repipe vs. rerouteYou are here
- 11Low pressure: the PRV, galvanized pipe, and the sequence that finds which one it is
- 12Sewer gas: trap seals, trap primers, vents, and the sequence that finds the smell
- 13Water treatment: where softeners are restricted in California, filtration, pressure regulators, and thermal expansion
- 14Fixtures and conservation: CALGreen flow rates, SB 407 retrofit-on-alteration and disclosure-on-sale, 1.28 gpf, and the ADA basics a plumber needs
- 15Materials and methods: PEX vs. copper vs. CPVC, ABS vs. PVC (it is regional), cast iron, and the transitions that fail
- 16Commercial basics: grease interceptors, the backflow program, and the tester certification that opens a second line of work
- 17Cal/OSHA for a small shop: the IIPP every employer must have, heat illness prevention, trenching and the 5-foot permit, confined space, silica, and ladders
- 18Environmental rules: EPA lead-safe certification for any pre-1978 home, asbestos and transite pipe, and stormwater
- 19Job-site craft: sequencing with the other trades, protecting the home, and the punch list that ends the job
- 20Case: the water heater that failed inspection twice
- 21Case: the gas leak call. The protocol, and the walk-away
- 22Case: the "customer doesn't want a permit" job
- 23Template: the job-site checklist, from the truck to the walk-through
- 24Template: the pre-inspection checklist by stage. Underground, rough, water heater final, gas, and trim
- 25Template: the Injury and Illness Prevention Program starter for a plumbing shop of one to five
- 26Template: the Heat Illness Prevention Plan for a plumbing shop, outdoor and indoor
- 27Template: the customer options sheet (good / better / best) with the cost band, the permit path, and the code trail on each rung