Plumbing Inspection Checklist for a Home You Are Buying

The short answer

Cutting to the chase: A general home inspection covers less of the plumbing than most buyers assume. The InterNACHI Standards of Practice require the inspector to run fixtures, flush toilets and check the water heater, and explicitly do not require inspecting wastewater treatment systems, water treatment systems, well pumps or tanks, safety or shut-off valves, floor drains, or determining whether the pipe is polybutylene or similar plastic, and state that an inspection will not identify concealed or latent defects. The buried sewer lateral falls squarely in that gap, which is why a sewer camera scope at HomeGuide's $125 to $500 sits against sewer line repair at $150 to $3,800 in the same dataset.

The short version: What a general home inspection misses in the plumbing, why a sewer camera scope changes purchase prices, and what unpermitted plumbing work means at resale.

What a general home inspection does cover

Start with what the buyer is paying for, because a general home inspection is a competent visual survey and worth having. Under the InterNACHI Standards of Practice the inspector shall inspect the main water and fuel shut-off valves, the water heating equipment including its energy source, venting connections and temperature and pressure relief valve, the interior water supply including all fixtures and faucets by running the water, all toilets by flushing them, all sinks, tubs and showers for functional drainage, the drain, waste and vent system, and drainage sump pumps with accessible floats.

The inspector must also describe whether the supply is public or private, the location of those shut-off valves, any observed fuel storage system, and the capacity of the water heating equipment where labelled.

That list catches real problems: a relief valve with no discharge pipe, a slow-draining tub, a shut-off valve nobody can find. What it cannot do is see anything not visible, and the plumbing in a house is mostly not visible.

The exclusions are where the money is

Standards of practice are written as much to bound liability as to define scope, and the exclusion list is the part buyers should read before the report arrives rather than after. The items below come from the InterNACHI Standards of Practice as things the inspector is not required to inspect or determine.

Read them against the way plumbing actually fails. Sewer laterals, buried water services and the pipe material inside the walls account for a large share of expensive surprises, and every one is either excluded outright or covered by the statement that an inspection will not identify concealed or latent defects.

• Wastewater treatment systems. On a septic property the entire disposal system is outside scope.
• Water treatment systems, water filters and water softeners.
• Safety or shut-off valves, floor drains, lawn sprinkler systems and fire sprinkler systems.
• The exact flow rate, volume, pressure, temperature or adequacy of the water supply.
• Water quality, potability or reliability of the supply or source.
• Testing for gas or fuel leaks, or indications of them.
• Whether polybutylene, polyethylene or similar plastic piping exists, or what condition it is in.
• Anything concealed, latent or not readily accessible, which covers most of the pipework in the building.

The sewer scope is the finding that moves prices

A sewer camera scope is a separate service performed by a plumbing company, and it is the highest-value add-on a buyer can order. A camera goes down the lateral from a cleanout and records the run from the building out to the connection at the public main, which is the part nobody else inspects and the homeowner owns outright.

The economics make the decision easy. HomeGuide's sewer camera data puts the national average at $280 across a $125 to $500 range, and $100 to $250 when added to a standard home inspection. In the same dataset sewer line repair runs $150 to $3,800 and full replacement $2,000 to $10,000. A finding either way changes the transaction by far more than the inspection costs.

Access is the practical variable. HomeGuide separates the price by access point: $125 to $500 where a cleanout exists, $175 to $750 where a toilet has to be pulled. A house with no accessible cleanout is itself a finding, because that cost recurs.

• Root intrusion at joints, the most common cause of recurring blockages in older laterals.
• Pipe material and condition: clay tile, cast iron, Orangeburg or plastic, each with a very different remaining service life.
• Whether a cleanout exists and where, which sets the cost of every future intervention.

Inspection costs against repair costs

The case for spending money on inspection before closing is that the two sides of this table are not close. Published inspection figures sit in the hundreds; the repairs they find sit in the thousands and are not negotiable once the deed has changed hands.

Unpermitted plumbing work, and what it costs later

Unpermitted work is plumbing installed without the permit and inspection the jurisdiction required. It is common in finished basements, added bathrooms, relocated laundry rooms and converted garages, and it is a resale problem rather than only a safety one.

In Arizona the permit question is answered locally, which makes it harder to research and more important to ask about. The code in force is the 2021 IPC and 2021 IFGC adopted as the Arizona Plumbing Code at 3 CCR 720-1, and local governments may amend it upward only.

The exposure comes in three forms. An insurer may take a different view of a loss originating in work that was never inspected. A future buyer's inspector or lender may flag it, which becomes a price conversation at the worst moment. And retroactive compliance can mean opening finished walls so an inspector can see the work.

• Request the permit history from the local building department, then walk it against the house.
• Look hardest at added bathrooms, basement wet bars, relocated laundry connections, and any water heater or gas appliance newer than the house.
• Look for a missing thermal expansion tank on a closed system, absent shut-off valves, and drain lines running uphill. These are the signatures of work nobody inspected.
• Get a licensed plumber's written opinion on what compliance would require before agreeing any credit, because the cost is driven by access rather than by the pipework.

Pipe material and age, which the report may not identify

The InterNACHI Standards of Practice state the inspector is not required to determine the existence or condition of polybutylene, polyethylene or similar plastic piping. That exclusion is worth pausing on, because pipe material is one of the strongest predictors of future plumbing cost and it is the item most likely to be missing from the report.

Age gives a first guess and no more. What settles it is a look at exposed pipe in a basement, crawl space or under sinks, where a plumber can usually identify supply material in a minute.

• Galvanised steel supply: internal scale and falling flow at upper fixtures rather than a leak, with a repipe as the eventual answer.
• Polybutylene supply: specifically excluded from the standard inspection scope, and worth asking about by name.
• Cast iron drainage: corrodes from the inside, so the failure mode is a thinned section, best assessed with a camera rather than by eye.
• Clay tile or Orangeburg sewer lateral: joint intrusion and deformation respectively, both camera findings. Mixed materials at transitions are where older houses leak first.

The checklist to hand to an inspector or plumber

Inspectors work to a standard of practice, which means anything beyond it has to be requested and usually paid for separately. Handing over a written list at booking is more effective than asking questions at the end of the walk-through.

1. Order a sewer camera scope of the full lateral to the public main, and ask for the recorded footage rather than a summary.
2. Ask for the location of the main water shut-off, the meter and the curb stop, and whether the main valve was operated or only observed.
3. Ask for the supply pipe material to be identified where visible, including whether polybutylene is present, since that determination sits outside the standard scope.
4. Ask for the water heater's age from the serial number, the condition of the relief valve discharge pipe, and whether a thermal expansion tank is present on a closed system.
5. Ask for exterior hose bibbs to be checked as frost-proof types with interior shut-offs, which matters through a long Arizona freeze-thaw season.
6. On a septic property order a separate septic inspection; on a well, order a well inspection and a full water test, since all of it is excluded.
7. Pull the permit history for the address and compare it against the plumbing physically present.

Turning a finding into a number

A finding is only useful if it converts into money, a repair or a decision to walk. What makes that work is a written scope from a licensed plumber rather than a paragraph in a report: a seller's agent can argue with a description and cannot easily argue with a quote.

Sewer findings carry the most leverage of any plumbing item: the buyer will own the lateral outright, the repair is disruptive, and HomeGuide's $2,000 to $10,000 replacement range is wide enough that nobody wants to inherit the uncertainty.

Three outcomes are normal and not equivalent. A price reduction hands the buyer cash and the whole problem. A seller repair means the work is done to the seller's standard by the seller's contractor. An escrow holdback keeps money aside against an agreed scope. The middle option needs the most care: specify the scope, the permit and the warranty in the contract.

• Get a written scope and price from a licensed plumber before naming a figure, then add contingency: access, restoration and permits are what push plumbing repairs past a quoted range.
• Where a seller repairs, name the scope, require the permit and inspection, and require the documentation at closing.

Where DIY ends and the licence begins

• No cleanout can be found and the camera could not be introduced. An unscoped lateral on an older property is an open question, not a clean result.
• Evidence of a previous basement backup: a stained floor drain surround, or replaced flooring in one area only.
• Plumbing present in the house that does not appear in the jurisdiction's permit record, particularly an added bathroom or a relocated gas appliance.
• A water heater relief valve with no discharge pipe, a capped discharge, or one terminating out of sight. That is an installation defect and a safety item.
• Galvanised supply piping combined with poor flow at upper fixtures. Price a repipe as a possibility before closing, not after moving in.

How Arizona handles this

Plumbing in Arizona is regulated by Arizona Registrar of Contractors (ROC). Contractor licensing in Arizona is state-level through the Arizona Registrar of Contractors, but building and plumbing code adoption and permitting are entirely local because Arizona has no mandatory statewide building code. Permitting is entirely local in Arizona. Many jurisdictions in the Maricopa County area accept residential equipment replacement permits through a shared online portal, and Pima County publishes a dedicated permit page for air-conditioning and water heater replacements - a useful reminder that swap

Arizona licensing and permit rules