In the Field · Part 4
Low pressure: the PRV, galvanized pipe, and the sequence that finds which one it is
"Low pressure" is the customer's word for three different problems: low static pressure from the street or a failed regulator, low flow from pipe that has closed up inside, and a fixture that is clogged at the aerator. Each has a different fix and a different price, and the gauge on the hose bibb tells them apart in the first five minutes. This lesson is the sequence: static, then flow, then isolate by fixture and by section, then the ladder, which runs from a $12 aerator to a whole-house repipe of galvanized pipe, with the pressure-reducing valve in the middle as both the most common cause and the most common cure.
What the full lesson covers
- Static pressure at the hose bibb with nothing running: under 40 psi is a supply or regulator problem; 40 to 80 is normal; over 80 requires a regulator by code (CPC 608.2). A regulator that reads low static has failed closed; one that reads high has failed open.
- Flow: open a second fixture while watching the gauge. A large drop under flow with normal static means restriction, which in a pre-1960s house means galvanized pipe closing up with rust and scale.
- Isolate: one fixture low is the fixture (aerator, cartridge, supply line, angle stop); one bathroom low is the branch; hot only is the heater's dip tube or nipples; everything low with good street pressure is the regulator or the main line.
- The ladder: clean or replace the fixture parts; replace the regulator (with the expansion tank the code requires); replace the failed branch; repipe the galvanized house, sized by fixture units.
- Never raise a regulator above 80 psi to "fix" flow; the code caps static at 80 and the flow problem is in the pipe.
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More lessons in The Field: Method, Code, and Cases
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- 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. reroute
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- 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
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- 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