Complete Plumbing Inspection Checklist (2026)

Turn the main shut-off valve fully closed, then open a faucet and verify water stops completely within 10 seconds. A valve that doesn't fully shut off is useless in an emergency. Gate valves (multi-turn) commonly seize or fail to seal after years of disuse. Ball valves (quarter-turn) are more reliable. If the main shut-off doesn't fully stop flow, replace it with a quarter-turn ball valve ($200–$500 installed) — this is the most important safety upgrade in any home's plumbing system.

Screw a $10 pressure gauge onto an outdoor hose bib and read the static pressure with no water running in the house. Normal residential pressure is 40–80 PSI. Below 40 PSI indicates a supply problem (corroded pipes, failing pressure regulator, municipal supply issue). Above 80 PSI causes stress on pipes, fittings, and appliances — a pressure reducing valve (PRV) is required ($150–$400 installed). Record the pressure reading for comparison in future inspections.

Examine exposed supply pipes in the basement, crawlspace, utility room, and under sinks. Note the pipe material: copper (green patina or shiny brown), galvanized steel (gray, often corroded at joints), PEX (flexible colored tubing), or CPVC (cream-colored rigid plastic). Look for green staining on copper (indicates pinhole leaks starting), white mineral deposits at joints (slow leaks), and rust/corrosion on galvanized pipes. Galvanized supply pipes in homes built before 1970 are the highest-priority replacement — they corrode internally, restricting flow and contaminating water.

Homes built before 1986 may have lead solder on copper pipe joints or a lead service line from the municipal main to the house. Lead service lines are dull gray and scratch bright silver with a key. Lead solder appears as thick, dull gray beads at copper joints (lead-free solder is shiny). If lead is present, get a water test ($20–$50 for a mail-in kit) to check lead levels at the tap. EPA action level is 15 parts per billion. Lead service line replacement costs $3,000–$8,000; some municipalities offer subsidized or free replacement programs.

Turn on the hot water at the fixture farthest from the water heater and time how long it takes for hot water to arrive. Under 60 seconds is good; over 2 minutes indicates long pipe runs, undersized pipes, or a water heater issue. Check the temperature with a cooking thermometer — it should be 120°F at the tap (the recommended setting that balances scald prevention and Legionella control). Temperatures above 130°F at the tap indicate the water heater thermostat is set too high.

Run water in every sink, tub, and shower for 30 seconds and observe drain speed. Water should drain completely within 10–15 seconds of shutting off the faucet. Slow drains indicate partial blockages, improper venting, or undersized drain pipes. Flush every toilet and verify it clears completely in a single flush with a strong swirl. A weak or incomplete flush suggests a partially blocked drain, deteriorated flush mechanism, or venting problem.

Sewer gas smell in the house indicates a dried-out trap (common in infrequently used floor drains and guest bathrooms), a cracked drain line, or a missing or damaged vent. Pour a gallon of water into every floor drain and infrequently used fixture to refill traps. If the smell persists after traps are refilled, the problem is a cracked pipe or vent deficiency — a plumber needs to smoke-test or camera-inspect the DWV system to locate the breach.

Examine exposed drain pipes in the basement and crawlspace. Cast iron drains in homes built before 1975 are the primary concern — look for rust, flaking, pitting, and sections where the pipe wall has thinned (you can see light through pinhole perforations). Cast iron drain pipes have a 50–75 year lifespan and many are now failing. Check that horizontal drain runs maintain a consistent downward slope (1/4 inch per foot minimum) — sections that sag or belly hold water and attract clogs.

Look at the roof for vent pipe terminations — every home should have at least one visible vent pipe (typically 3–4 inch PVC or cast iron). Vent pipes must extend at least 6 inches above the roof surface and be unobstructed. Bird nests, leaves, ice, and debris can block vents, causing slow drains and gurgling sounds throughout the house. From inside the attic, verify vent pipes run continuously from the drain system to the roof without disconnections or gaps.

Find the serial number label on the water heater and decode the manufacture date (most brands encode the date in the first 4 characters of the serial number — check the manufacturer's website for their format). Tank water heaters have a 10–15 year lifespan. Units over 10 years old should be monitored closely; over 12 years, budget for replacement. A water heater that fails catastrophically can dump 40–80 gallons onto your floor in minutes.

Rust or corrosion on the tank body, around fittings, or at the base indicates internal deterioration. Water stains on the floor beneath the tank suggest a slow leak from the tank, T&P relief valve, or supply connections. Any visible rusting on the tank body means the internal glass lining has failed and the steel tank is corroding — replacement is needed before the tank ruptures.

The T&P relief valve is a safety device that releases water if the tank pressure or temperature exceeds safe limits — preventing a potential explosion. Lift the lever on the T&P valve and verify water flows from the discharge pipe, then release and verify it seals completely. If it doesn't flow when lifted, it's stuck and must be replaced ($15–$30 for the valve, $75–$150 installed). If it drips continuously after testing, it also needs replacement. The discharge pipe must terminate 6 inches above the floor or drain to the exterior — never capped, plugged, or connected to a closed system.

The sacrificial anode rod protects the tank from corrosion by corroding in place of the steel tank. It should be inspected every 3–5 years and replaced when more than 50% corroded (core wire visible for more than 6 inches). Removing the anode requires a 1-1/16-inch socket and breaker bar — it's often corroded tight. A new anode rod costs $20–$50; professional replacement costs $100–$250. Replacing the anode can extend tank life by 5+ years.

Sediment (mineral deposits from hard water) accumulates at the bottom of the tank, reducing efficiency and accelerating corrosion. Connect a garden hose to the drain valve at the base, run it to a floor drain or exterior, open the valve, and let water flow until it runs clear. If the water is heavily discolored or contains chunks of sediment, annual flushing is needed. If the drain valve is stuck or won't seal after opening, it needs replacement before the next flush.

Open every sink cabinet and look at the underside of the sink, supply line connections, drain connections, P-trap, and garbage disposal (if present). Feel for moisture on pipes and at joints. Look for water stains, warped cabinet bottom, or mold growth — these indicate a current or recent leak. Supply line connections and P-trap joints are the most common leak points under a sink.

Listen for running water after each toilet finishes filling — a running toilet wastes 200+ gallons per day and usually needs a $10 flapper replacement. Rock the toilet gently side to side — any movement indicates loose closet bolts or a deteriorated wax ring, both of which allow sewer gas and water to escape at the base. Check around the toilet base for water stains or soft/discolored flooring — signs of a wax ring failure leaking into the subfloor.

Rubber washing machine supply hoses are the number one cause of catastrophic residential water damage — they burst without warning, flooding the laundry area at full municipal pressure. Replace rubber hoses with braided stainless steel hoses ($15–$25 per pair) every 5 years or immediately if you see bulging, cracking, or corrosion at the fittings. Turn off the supply valves when the washing machine isn't in use to reduce pressure on the hoses 24/7.

Turn each individual fixture shut-off valve off and on to verify it operates and fully stops flow. Supply valves that are seized, leaking, or won't fully close are useless in an emergency and should be replaced. Multi-turn gate valves (the most common type in older homes) fail frequently — quarter-turn ball valves ($5–$15 per valve, $75–$150 installed) are the reliable replacement. Do this test annually to prevent valves from seizing.

A sewer camera inspection ($150–$400) sends a video camera through the sewer lateral to inspect the pipe condition from inside. It reveals root intrusion, pipe cracks, joint separation (offsets), bellies (sagging sections that hold water), and material deterioration that can't be detected from the surface. For homes with clay, Orangeburg, or cast iron sewer pipes, a camera inspection is essential before buying or as part of a maintenance plan. The video recording serves as a baseline for tracking deterioration over time.

The sewer cleanout is a capped pipe (usually 4-inch) that provides access to the sewer lateral for cleaning and inspection. It's typically located near the foundation wall on the side of the house facing the street, or in the basement/crawlspace. If you can't find a cleanout, one should be installed ($200–$600) — without it, sewer cleaning requires pulling a toilet or accessing the line through the roof vent, adding time and cost to every future service call.

Turn on each exterior hose bib and check for leaks at the handle packing, at the wall penetration, and at the spout. Leaks at the wall penetration indicate the pipe inside the wall is damaged — often from freeze damage. Frost-free (anti-siphon) hose bibs are required by code in freezing climates — they shut off water inside the heated wall rather than at the exterior, preventing freeze damage. If your hose bibs are the old short-stem type, upgrading to frost-free models ($100–$250 installed each) prevents the most common cold-weather plumbing failure.

Slab leaks — leaks in supply or drain pipes running under or through the concrete foundation — are expensive to repair ($1,500–$5,000) and difficult to detect. Warning signs: unexplained increase in water bills, warm spots on the floor (hot water line leak), the sound of running water when all fixtures are off, cracks in the foundation or flooring, and mold or moisture on flooring. Check the water meter with all fixtures off — if the flow indicator moves, water is running somewhere it shouldn't be. A plumber can pinpoint slab leaks with electronic listening equipment or infrared cameras.