Before any wall in a new house gets covered, its drain piping has to prove it doesn’t leak. Under the residential code most Arizona towns now follow, the crew fills the drain, waste and vent system with water to a level well above the pipe being tested and holds it there for 15 minutes. They can also pressurize it with 5 psi of air for the same length of time. The water lines and the gas piping each get a separate test. Every one of these has to pass while the pipe is still exposed.
In the White Mountains, the calendar adds a layer that builders in Phoenix don’t deal with. Ground freezes, dirt roads turn to mud in spring, and the inspector’s schedule fills quickly once building season opens. If a crew misses a test window in late fall, underground work can sit until the thaw. On a mountain build, the plumbing schedule is planned around when each inspection can realistically happen.
Many builders call ABS Plumbing Co for gas piping and drain cleaning first, and then bring the same licensed crew back for Pinetop-Lakeside residential new construction. That means one plumber is responsible for the house from the first trench to the last faucet. The shop on White Mountain Boulevard also covers Show Low, Snowflake, Springerville and White River, which helps when stage work and inspection dates have to fit inside one building season. If you already have home plans, send them in and ask for a rough-in estimate before excavation starts.
What Has to Be Settled Before the First Trench?
The paperwork stage decides how smoothly everything after it goes. The Town of Pinetop-Lakeside building permit requirements call for plumbing plans in the permit set. The town also needs Sanitary District approval when the house will connect to sewer, or a county health permit when it will use a septic tank. The town currently builds to the 2024 editions of the International Codes, so those editions set every test number that follows.
Before mobilizing, a professional crew confirms a few handoffs:
- The sewer or septic approval matches where the plans show the building drain leaving the slab.
- Fixture locations on the plans are final, because moving a toilet after the slab is poured means cutting concrete.
- The foundation contractor knows where pipe sleeves need to pass through footings.
How Does a Crew Handle the Underground and Slab Stage?
This is the stage that can’t be redone cheaply. The crew lays out the building drain, branch lines and stub-ups from the plans. Then they trench, set the pipe to grade, and bring each stub-up to the exact spot where a fixture will sit once the house is framed. When the concrete is poured, those positions are fixed for good.
Slope is the first thing an inspector checks under a slab. Drain pipe 2-1/2 inches and smaller needs a quarter inch of fall per foot. Larger pipe typically runs at an eighth of an inch per foot. A drain that’s too flat lets solids settle and becomes a drain cleaning call within a few years.
Before the crew calls for the underground inspection, they confirm:
- Test plugs are seated at every opening, with a standpipe rising high enough to create the required water column.
- The water level holds for the full 15 minutes with no drop at the standpipe.
- The pipe sits on firm, even bedding with no rocks pressing against it, since White Mountains soil is full of volcanic cinder and stone.
- Sleeves protect the pipe where it passes through concrete footings.
- The water service trench is deep enough to stay below local frost depth.
The handoff is simple. Nothing gets backfilled and no concrete gets poured until the inspector approves the work. In cold months, crews try to schedule this inspection for midday so the water in the test doesn’t freeze before the inspector arrives.
What Gets Tested While the Walls Are Still Open?
Rough-in starts once framing is done and the roof is on. The crew runs vent stacks through the roof, branch drains to every fixture, and hot and cold supply lines throughout the house. At this point the inspector can see the whole system, which won’t be true again.
The drain test is tougher than it used to be. When the code was updated in 2021, the required water column for testing drain, waste and vent piping went from 5 feet to 10 feet, because a lower column can miss leaks at upper joints. The supply lines are tested separately, either with water at the system’s working pressure or with air at 50 psi for 15 minutes. Air can only be used where the pipe manufacturer allows it, since some plastics prohibit compressed air testing.
At the rough-in inspection, the inspector typically looks for:
- Vent terminations at the required height and distance from windows and openings.
- Steel nail plates anywhere pipe runs within 1-1/4 inches of a stud’s edge.
- Cleanouts that will still be reachable once walls and cabinets are installed.
- Proper pipe supports and fixture drain arms that stay within allowed lengths.
- A test gauge whose range fits the pressure being measured.
Cold weather causes more failed tests than bad joints do. Water left standing in lines inside an unheated frame can freeze overnight and split a fitting. Experienced crews drain supply lines right after the inspector signs off, or they schedule rough-in for after temporary heat is running.
Why Does the Gas Line Get Its Own Pressure Test?
Gas piping is tested on its own terms because a leak there is a safety problem, not just a water damage problem. The test uses air or an inert gas, never fuel gas or oxygen. The pressure has to be at least one and a half times the system’s maximum working pressure and no lower than 3 psig. In a single-family home, it has to hold for at least 10 minutes. Many inspectors ask for a higher pressure or a longer hold than that minimum.
Before charging the line, the crew makes sure of the following:
- Appliances and regulators are isolated or disconnected so test pressure can’t damage their valves.
- Every outlet is capped or plugged, including stub-outs for a future range or fireplace.
- The gauge reads in increments small enough to show a small pressure drop.
- Corrugated stainless tubing is bonded according to the manufacturer’s instructions.
Mountain homes add their own details. Many homes outside the gas mains run on propane, so the supplier sets the tank while the plumber tests everything downstream of the regulator. Leak checks are stricter now too. The 2024 fuel gas code requires any gas detector used for leak detection to be listed for that purpose.
How Does Trim-Out Lead to the Final Sign-Off?
Once drywall, paint and cabinets are done, the plumbers return for trim-out. They set toilets, faucets and the water heater, connect appliances, and flush the supply lines so construction debris doesn’t end up in new aerators. Then the gas piping is purged of test air and appliances are lit for the first time, with a combustible gas detector watching the discharge point.
The final plumbing inspection usually happens alongside the building final, and the certificate of occupancy depends on both. In a mountain town, the best schedules aim to finish before the first hard freeze, or they make sure permanent heat is running before water sits in fixture traps. Homes that pass on the first try are usually the ones where each test was scheduled around the season, rather than squeezed in whenever the inspector had an opening.
