New Home Plumbing Inspection Checklist — What to Check Before Closing

Use a pressure gauge on an outdoor hose bib or laundry connection. Pressure below 40 PSI indicates a supply line restriction, failing pressure regulator, or municipal supply issue. Pressure above 80 PSI stresses pipes, fittings, and appliances — a pressure reducing valve (PRV) is needed. Check pressure with no fixtures running, then re-check with two fixtures running simultaneously to identify supply bottlenecks.

Pipe material tells you the remaining lifespan of the supply system. Copper lasts 50–70 years and is ideal. PEX lasts 40–50 years. CPVC is adequate but brittle with age. Galvanized steel corrodes internally and should be replaced if over 40 years old — it restricts flow and contaminates water with rust. Polybutylene (gray plastic, common 1978–1995) is a deal-breaker: it fails unpredictably and most insurers won't cover homes with it. Full repipe costs $4,000–$15,000 depending on home size.

The main shutoff is your emergency stop for the entire home. Turn it fully closed and verify water stops at all fixtures. If it won't close fully, leaks when closed, or the handle is frozen, it needs replacement before you move in. A failed shutoff during a burst pipe turns a $500 repair into a $20,000 flood. Gate valves (round handle) are less reliable than ball valves (lever handle) — note the type.

Inspect exposed pipes in the basement, crawlspace, and utility areas. Look for green/white corrosion on copper fittings (pinhole leaks developing), rust stains on galvanized pipes, hose clamps or rubber patches (amateur leak fixes that will fail), and mismatched pipe materials joined without proper dielectric unions (causes galvanic corrosion). Each of these indicates deferred maintenance and future repair costs.

In a properly functioning system, hot water should reach the farthest fixture within 60–90 seconds. Longer waits indicate undersized supply lines, excessive pipe runs, or a water heater at end of life. Homes with recirculating pumps should deliver hot water in under 15 seconds. Excessively long waits waste water and signal issues with the distribution layout.

Find the manufacturer's data plate on the side of the unit. The serial number encodes the manufacture date (first four digits are typically month and year). Tank water heaters over 10 years old are in their failure window. If the unit is over 12 years old, budget $1,500–$3,500 for replacement within 1–2 years. A leaking water heater that fails catastrophically can dump 40–80 gallons of water in minutes.

Rust at the base of a tank water heater means the tank is corroding internally — replacement is imminent (weeks to months). Mineral deposits or corrosion at the temperature and pressure relief valve indicate it's been discharging due to excess pressure or overheating. Corroded fittings at the top of the tank where supply lines connect suggest the anode rod is depleted and the tank is deteriorating.

The T&P relief valve is a critical safety device. It must have a discharge pipe running downward to within 6 inches of the floor or to an exterior drain — never capped, plugged, or discharging upward. A missing or improperly installed discharge pipe is a safety hazard and a code violation. Replacement is simple ($20 in parts) but its absence suggests other code shortcuts.

Gas water heaters produce combustion gases including carbon monoxide. The vent pipe must slope upward continuously to the chimney or roof penetration with no sags, dips, or disconnected joints. Single-wall vent pipe must maintain proper clearance from combustibles (6 inches typically). Atmospheric vented heaters in tightly sealed homes can backdraft, pulling combustion gases into living spaces. A CO detector near the water heater is essential.

Fill every sink, run every shower, and flush every toilet within a 5-minute window. Slow drainage or gurgling at one fixture when another drains indicates a blocked or undersized drain line. Backups at the lowest fixtures (basement floor drain, ground-floor shower) suggest a main sewer line issue. Individual slow drains are usually simple clogs ($150–$300 to clear); main line issues can cost $3,000–$10,000+.

A camera inspection ($250–$500) reveals the condition of the underground sewer line from the house to the city connection. It identifies root intrusion, bellied (sagging) sections that collect waste, offset joints, cracks, and collapses. In homes over 30 years old, clay or cast iron sewer lines are common failure points. A full sewer line replacement costs $5,000–$15,000. This single inspection has the highest ROI of any pre-purchase plumbing evaluation.

Modern drain systems use PVC or ABS plastic (80+ year lifespan). Older homes may have cast iron (50–75 year lifespan, check for corrosion and scale buildup), galvanized steel drains (30–50 years, corrodes internally), or even clay tile in the sewer line. Cast iron drain pipes with heavy external corrosion or visible holes need replacement. Mixed materials are common in renovated older homes — verify transitions are properly fitted.

Every fixture drain needs a P-trap — the curved pipe section that holds water to block sewer gas from entering the home. Missing P-traps (common under laundry sinks and bar sinks), S-traps (an outdated configuration that siphons dry), and drum traps (old-style traps that clog easily) are all issues. Missing traps are code violations and health hazards. Sewer gas contains methane and hydrogen sulfide.

Open every cabinet under every sink and look for: active drips, water stains on the cabinet floor, warped or swollen cabinet material, mold or mildew smell, and corroded supply valves. Feel the supply lines and drain connections with your hand — even small drips are detectable by touch. Under-sink leaks are the most common source of hidden water damage in homes.

Flush each toilet and listen: the tank should refill and stop within 60 seconds. Running water after the tank fills means a failed flapper or fill valve ($10–$30 repair). Rock the toilet gently — any movement means the wax ring seal is compromised, allowing sewer gas and water to escape at the base. A rocking toilet on a tile floor can crack the flange (the drain fitting in the floor), turning a $10 wax ring job into a $300–$500 flange replacement.

Rubber washing machine hoses are the leading cause of catastrophic residential water damage. They burst without warning after 3–5 years, flooding at full supply pressure. Check for bulging, cracking, or corrosion at the fittings. Stainless steel braided hoses ($20–$30 per pair) last 8–10 years and resist bursting. Also verify the drain hose is properly secured in the standpipe — a loose drain hose floods the laundry room every cycle.

The dishwasher drain hose must loop up to the underside of the countertop (high loop) or connect through an air gap device on the sink before joining the disposal or drain. Without this, dirty sink water can siphon back into the dishwasher. A missing high loop is a code violation in most jurisdictions and a sanitation issue. The fix is simple (reposition the hose and secure it) but its absence suggests shortcuts elsewhere.

Turn on each outdoor faucet and check flow rate, leaks at the handle or spout, and whether the anti-siphon vacuum breaker (if present) is intact. Frost-free hose bibs should have their shutoff inside the home — verify each interior shutoff operates. Leaking outdoor faucets waste water and cause foundation erosion. In cold climates, a frost-free hose bib that doesn't drain properly will freeze and crack.

Slab leaks (supply or drain pipe failures under the concrete foundation) are expensive disasters: $2,000–$6,000 for detection and repair, plus potential foundation damage. Warning signs: unexplained high water bills, hot spots on the floor (hot supply leak), sounds of running water when nothing is on, cracks in the foundation, or damp carpet/flooring without a visible source. If you suspect a slab leak, request a pressure test of the supply lines before closing.

A sewer cleanout is a capped pipe (usually 4 inches, white PVC or cast iron) near the foundation or in the yard that provides access to the main sewer line for snaking and camera inspection. Homes without an accessible cleanout require the plumber to pull a toilet to access the drain — adding $150–$300 to every service call. If no cleanout exists, installing one costs $300–$600 and is well worth the investment.