New Construction Plumbing Inspection Guide

A new construction plumbing inspection is an independent check of the pipes, drains, fixtures, and water heater in a newly built home, done by an inspector or plumber you hire rather than the builder. Many buyers skip it because the home is brand new and the city already inspected it. That is a mistake. City inspectors check for code compliance, not quality, and they spend a few minutes at each visit. A private inspection catches the mistakes that get buried behind drywall: a drain pipe with no slope, a vent that was never connected, or a water line run too close to a heat source. Finding those problems before closing costs a few hundred dollars. Finding them after move-in can cost thousands.

Why New Homes Still Need a Plumbing Inspection

New homes have plumbing problems more often than buyers expect. Builders work on tight schedules with multiple subcontractors, and plumbing crews may be rushed or staffed with less experienced workers. The city inspector visits briefly and checks a sample of the work against the building code. The code sets minimum safety standards, not good workmanship. A drain line that meets code but has a poor slope will still drain slowly. A vent that is technically connected but undersized will still gurgle. These are the defects a private inspector finds and a city inspector misses.

The builder warranty is not a substitute for an inspection either. Most builder warranties cover plumbing defects for one to two years, but using the warranty means living in the home while the builder schedules repairs, cuts into finished walls, and disrupts your life. A defect found before drywall is fixed in an afternoon with no damage to finishes. The same defect found after move-in means cutting drywall, matching paint, and possibly replacing flooring. The inspection is cheap insurance against that disruption.

There is also a simple timing advantage. Before closing, the builder is motivated to fix problems quickly so the sale completes. After closing, the builder is motivated to argue that the problem is minor or caused by the homeowner. An independent inspection report with photos gives you leverage while it matters most. Buyers of new homes should also review the plumbing disclosure requirements that apply when they later sell, since the condition of the original plumbing will matter then too.

The Three Inspection Phases

A complete new construction plumbing inspection happens in three phases that match the building schedule. The first is the rough-in inspection, done after the pipes are installed but before the walls are closed. The inspector checks the drain, waste, and vent piping, the water supply lines, and the locations of fixtures. This is the most important phase because every pipe is still visible. Mistakes found here are cheap to fix.

The second phase is the pre-drywall inspection, done after rough-in and just before drywall goes up. In many builds this is combined with the rough-in check, but when the schedule allows a separate visit, the inspector verifies that nothing was damaged or moved after the rough-in, that nail plates protect pipes where they pass through studs, and that the system passed its pressure test. A pressure test holds water or air in the drain system to prove there are no leaks in the joints. Ask your inspector whether a pressure test result was recorded.

The third phase is the final inspection, done after fixtures are installed and the home is nearly complete. The inspector runs every faucet, flushes every toilet, checks water pressure, tests the water heater, and looks for leaks at every connection. This is the phase most similar to a standard home inspection, and it is the one most buyers get if they only hire an inspector once. It is valuable, but it cannot see the pipes inside the walls. For the best protection, schedule all three phases. Our home inspection hub explains how each phase fits into the overall buying process.

What Inspectors Check at Each Phase

At rough-in, the inspector checks the drain layout first. Every drain needs the correct slope, usually a quarter inch per foot, so wastewater flows by gravity. Too little slope and waste sits in the pipe. Too much slope and water outruns the solids, leaving clogs behind. The inspector checks that ABS drain pipe joints are properly glued with no dry fits, that horizontal runs are supported, and that cleanouts are installed where the code requires them. Vent pipes are checked for correct size and routing, because a vent that terminates in the wrong place can let sewer gas into the home.

Water supply lines are checked for material, size, and protection. The inspector looks for kinks in PEX lines, for copper lines touching concrete without protection, and for shutoff valves at each fixture. The location of the main shutoff and the water heater connections are noted. Gas lines, where present, are checked for proper support and shutoff valves. The inspector also confirms that the pipes are kept away from heating ducts and electrical panels where they could be damaged.

At the final inspection, the work shifts to the fixtures. The inspector runs hot and cold water at every tap and checks that hot water arrives in a reasonable time. Toilets are flushed several times to check for rocking, leaks at the base, and proper fill levels. Showers and tubs are checked for drainage speed and for leaks around the drain and faucet trim. The water heater is checked for age, venting, the temperature and pressure relief valve, and whether an expansion tank is installed. The inspector also tests the dishwasher and garbage disposal connections and looks under every sink for drips.

New Construction Plumbing Inspection Cost in 2026

Prices depend on the region, the size of the home, and how many phases you book. A single final inspection is the cheapest option, while a full three-phase package gives the best coverage. The table below shows typical 2026 US pricing.

Most buyers who hire a full home inspector for the final phase pay $400 to $700 for the whole house. Adding a dedicated plumbing rough-in inspection for $200 to $400 brings the total to roughly $600 to $1,100 for complete coverage. On a $400,000 home, that is about a quarter of one percent of the price. One hidden plumbing defect, such as a misconnected drain that floods a bathroom, can easily cost $3,000 to $8,000 to repair after move-in. The math strongly favors the inspection.

Common Plumbing Defects in New Builds

Inspectors see the same defects in new construction again and again. Poorly sloped drain lines are near the top of the list. A drain that runs flat or slopes backward will hold water and waste, causing slow drains and recurring clogs that no amount of drain cleaner will fix. The repair requires opening the wall or floor, which is exactly why the rough-in inspection matters.

Missing or undersized vents are another frequent finding. Every fixture drain needs a vent to the roof so air can enter the system and sewer gas can escape. When a vent is forgotten or connected to the wrong pipe, drains gurgle, traps dry out, and odors enter the home. A related defect is an ABS drain joint that was glued without primer or with too little cement. The joint may hold during the pressure test and fail months later when the pipe expands and contracts with hot water.

Other common defects include water heater venting that is too short or poorly sealed, missing nail plates where pipes pass through studs, supply lines run without insulation in exterior walls, and fixtures installed with the hot and cold lines reversed. Reversed supply lines are easy to spot at the final inspection and cheap to fix, but they are also easy to miss if nobody runs the water. A pre-listing plumbing inspection years later will catch the same defects, but by then the builder warranty may have expired.

How to Use the Report With Your Builder

When the inspector finds defects, send the written report and photos to the builder in writing, not just in a phone call. Ask for a written response with a repair schedule. Most builders fix legitimate defects before closing without argument, because the report is factual and the fix is cheaper now than under warranty later. Keep copies of everything: the inspection report, your message to the builder, and the builder's response.

If the builder disputes a finding, ask your inspector to explain the defect in writing with a reference to the relevant code section or manufacturer instruction. Builders respond to documented findings far more readily than to opinions. If the builder refuses to fix a real defect, talk to your real estate agent and your attorney before closing. You may be able to delay closing, negotiate a credit, or require an escrow holdback for the repair.

After the repairs are done, ask the inspector to return for a re-inspection of the corrected items. A re-inspection visit usually costs $100 to $200 and confirms that the work was actually done and done correctly. Do not accept the builder's word alone that a hidden defect was fixed, because you cannot see the repair behind the drywall. Once you close, read how to read the plumbing section of an inspection report so you understand the language inspectors use if you ever need a follow-up visit. Your inspection report is also useful documentation for the future, since it records the condition of the plumbing on the day you bought the home.

Buying a new home is a major investment, and a plumbing inspection protects it. If you need a licensed plumber to inspect a new build or check a repair, call (877) 762-1902 for help.