Plumbing Inspection Checklist

A plumbing inspection is a systematic walk-through of a property's supply, fixture, drainage, and venting systems to document current condition, catch developing problems, and give the customer a clear, honest picture of what needs attention now versus what to watch. Use the room-by-room task lists below to run a consistent inspection on every visit, no matter who is holding the flashlight.

This is a general educational checklist for field reference only. It is not a substitute for your local plumbing code, manufacturer installation and service procedures, or the judgment of a licensed plumber. Code requirements, permit rules, and licensing vary by jurisdiction — always defer to the authority having jurisdiction and follow the equipment manufacturer's documentation.

Why a standard inspection matters

A repeatable inspection does three things well. First, it catches problems early — a weeping supply valve, a slightly elevated static pressure, or a water heater without a functioning expansion tank are cheap to address now and expensive to ignore. Second, it documents condition at a point in time, which protects both you and the customer if something fails later and is invaluable for real-estate transactions, warranty claims, and insurance. Third, a thorough walk-through surfaces legitimate work and lets you quote it transparently instead of relying on a single presenting complaint.

Consistency is the point. When every technician follows the same sequence and captures the same photos and readings, your findings become comparable over time and far more credible to the customer. For how to price the work you uncover, see the plumbing pricing guide. For a broader look at how inspections fit into dispatch, work orders, and scheduling, see what is field service management.

Before the visit

• Confirm the reason for the visit and any specific complaint (leak, low pressure, no hot water, odor). Sets your priorities and tells you where to look hardest.
• Verify the property type, approximate age, and any prior service history. Older systems and past repairs point to likely failure modes.
• Locate and confirm the main water shutoff before you touch anything. You cannot safely test if you cannot stop the water fast.
• Confirm you have a working pressure gauge, flashlight, moisture meter or paper towel, camera, and drain-safe test tools. A missing gauge turns a measurement into a guess.
• Ask permission before operating shutoffs, valves, and appliances, and note anything the customer says is fragile or already known-bad. Old valves can fail when exercised — set expectations first.

Water supply & pressure

• Read and record static water pressure at a hose bib or laundry connection. Most residential systems target a moderate range; readings that run high stress the whole system. Confirm acceptable ranges against local code and fixture ratings.
• Check for a pressure-reducing valve (PRV) and note its presence, age, and any signs of failure. A failed PRV is a common cause of pressure that is too high or unstable.
• Confirm the main shutoff operates smoothly and fully stops flow. A stuck or partial main is a safety problem during any repair.
• Inspect visible supply piping for material type, corrosion, mineral buildup, and prior repairs. Pipe material and corrosion drive both risk and cost.
• Look for signs of water hammer or excessive noise when valves close. Persistent hammer can loosen joints over time.

Fixtures (faucets, toilets, showers/tubs)

• Run each faucet hot and cold; check flow, temperature response, and drips at the spout and handle. A slow or lopsided flow points to aerator, cartridge, or supply issues.
• Inspect under and around each faucet base and supply connection for moisture. Slow leaks show up here long before the customer notices.
• Test each toilet: flush performance, refill time, running water, and rocking at the base. A rocking toilet or a running fill valve wastes water and can hide a failing wax seal.
• Check toilet shutoff valves and supply lines for corrosion and weeping. These valves are frequent slow-leak sources.
• Inspect showers and tubs for drainage speed, diverter function, caulk/grout condition, and leaks at the valve. Failed caulk and slow drains lead to hidden water damage.
• Note fixture age and any mismatched or non-standard parts. Non-standard parts affect repair time and availability.

Water heater

• Identify type (tank, tankless), fuel source, capacity, and approximate age from the label. Age and type shape both risk and replacement conversation.
• Inspect the temperature and pressure relief (T&P) valve and its discharge line for correct routing and any signs of discharge. The T&P valve is a critical safety device — never leave it capped or obstructed. Verify routing against local code.
• Check for an expansion tank where required and confirm it appears functional. A closed system without proper expansion control can over-pressurize.
• Look for corrosion, rust stains, or moisture at the base, fittings, and connections. Rust at the base often signals a tank nearing end of life.
• For gas units, visually check venting, combustion air, and general flue condition, and note anything questionable for follow-up. Improper venting is a serious safety concern; escalate rather than guess. Follow the manufacturer's procedures and local code.
• Record set temperature and any signs of sediment (rumbling, slow recovery). High temperature and heavy sediment reduce efficiency and lifespan.

Drains, waste & vents

• Test drainage speed at each sink, tub, and shower. A slow drain is the most common early sign of a developing blockage.
• Listen for gurgling and watch for bubbling at fixtures when others drain. Gurgling often indicates a venting problem, not just a clog.
• Check for sewer or sulfur odors and inspect accessible traps for dry seals or leaks. A dry or leaking trap lets sewer gas into the living space.
• Inspect visible waste piping and cleanouts for leaks, corrosion, and prior repairs. Waste-line leaks cause the most damage when hidden in cabinets or crawlspaces.
• Note the location and accessibility of cleanouts. Knowing where they are speeds any future drain service.

Under-sink & supply lines

• Open each vanity and kitchen cabinet and inspect for active leaks, staining, warping, and mold. Cabinets trap moisture and reveal problems the customer never sees.
• Inspect flexible supply lines (braided or otherwise) for age, kinks, corrosion, and bulging. Burst supply lines are a leading cause of catastrophic water damage.
• Check angle stops / shutoff valves for smooth operation and weeping. Seized stops make every future repair harder and riskier.
• Inspect the P-trap, disposal connections, and dishwasher/appliance hoses for leaks. Appliance connections loosen over time and drip quietly.
• Confirm any water filtration or softener connections are dry and secure. Add-on equipment introduces extra joints that can fail.

Exterior / hose bibs & shutoffs

• Operate each exterior hose bib and check for leaks at the valve and where it enters the wall. Freeze damage frequently shows up here after winter.
• Confirm the presence and condition of a backflow prevention device or vacuum breaker where applicable. Backflow protection guards the potable supply. Requirements vary by jurisdiction.
• Check for a frost-proof design or a dedicated interior shutoff in freeze-prone climates. Prevents split pipes and interior flooding.
• Inspect any irrigation or exterior connections for leaks and proper isolation. Exterior leaks can go unnoticed for months.

Sump pump / where applicable

• Confirm the sump pump powers on when the float is lifted and shuts off cleanly. A stuck float is the most common reason a pump fails when needed.
• Inspect the discharge line for proper routing, freeze protection, and unobstructed flow. A blocked or frozen discharge makes the pump useless.
• Check for a check valve and note any battery backup or alarm. Without a check valve, water can flow back into the pit.
• Look at the pit for debris, sediment, and standing water level. Debris shortens pump life and can jam the impeller.

Finish the visit / documentation & recommendations

• Photograph every issue found, plus the water heater label, pressure reading, and main shutoff location. Photos make your findings credible and easy to revisit.
• Record measurements (pressure, water heater age and set point) in writing, not from memory. Numbers you write down are numbers you can defend.
• Categorize each finding as safety/urgent, recommended, or monitor. Clear priority helps the customer decide without pressure.
• Review findings with the customer in plain language and note what they approve or decline. Documented decisions protect everyone later.
• Leave a written summary and any recommended follow-up. A tangible record turns an inspection into future work.

Red-flag quick reference

Common mistakes

• Inspecting only the complaint. The presenting issue is a starting point, not the whole job. Run the full sequence every time.
• Skipping the pressure reading. Pressure is quick to measure and explains a surprising number of downstream symptoms — don't guess it.
• Ignoring the water heater's safety devices. The T&P valve and venting are safety-critical. If anything looks wrong, escalate; do not improvise.
• Not photographing findings. A finding without a photo is hard to justify and easy for the customer to forget.
• Exercising old valves without warning. Old shutoffs can fail when operated. Set expectations first and be ready to stop water.
• Treating this list as code. A checklist keeps you thorough; it does not replace local code, permits, or manufacturer procedures.

FAQ

How long should a plumbing inspection take? It depends on property size, accessibility, and condition — a small home with easy access goes quickly, while a larger or older property with crawlspaces takes longer. Budget enough time to run the full sequence rather than rushing to the complaint.

How often should a property have a plumbing inspection? There's no universal rule, and the right interval varies with age, water quality, and prior issues. Many operators suggest a periodic check-up and an inspection around real-estate transactions or after a known problem — confirm what makes sense locally.

Does an inspection guarantee nothing will fail? No. An inspection documents observable condition at a point in time and flags developing issues; it cannot predict every hidden or sudden failure. Be clear with customers that it reduces risk rather than eliminating it.

For the equipment-side companion to this list, see the HVAC maintenance checklist.