Plumbing Inspection Before Buying a Home: What to Check and Why
A standard home inspection gives the plumbing maybe twenty minutes: run the faucets, flush the toilets, glance at the water heater. Yet plumbing hides some of the most expensive surprises a buyer can inherit — a failed sewer lateral or a house that needs repiping can each run well into five figures. For a few hundred dollars, a dedicated plumbing inspection turns those unknowns into negotiating points. Here is what to check before you remove contingencies.
The sewer scope: the single best money spent
A sewer scope — a camera run through the lateral from the house to the street — typically costs $150-$500 and is worth it on almost any home more than a couple of decades old. It reveals root intrusion, offset joints, bellies (sags where waste pools), and collapsed sections of clay or Orangeburg pipe.
Why it matters: a full lateral replacement commonly costs anywhere from several thousand dollars to $15,000 or more with street work involved — see our sewer line repair cost guide. Discovering that before closing means the seller fixes it or the price reflects it. Discovering it after means you own it. Note that some California cities also require a sewer lateral certification at point of sale, so ask your agent what applies locally.
Supply pipe material: what is the house made of?
Ask the inspector — or check exposed pipes at the water heater, under sinks, and in the crawl space — for the supply pipe material:
- Copper: the long-lived standard for decades; generally good news, though very old copper can pit.
- PEX: the modern flexible standard; normal in newer or repiped homes.
- Galvanized steel (common pre-1960s): corrodes from the inside, choking pressure and eventually leaking. A galvanized house is a repiping candidate — budget accordingly with our repiping cost guide, since whole-house repipes in California commonly run $4,000-$15,000+ depending on size and finish repairs.
- Polybutylene (roughly 1978-1995): a known-defective material that insurers dislike; treat it as a repipe waiting to happen.
Water heater: age, condition, and code
Find the manufacture date on the data plate (often encoded in the serial number). Tank water heaters typically last 8-12 years; one at year ten is a near-term expense of roughly $1,500-$3,500 installed — details in our water heater installation guide. Also look for rust streaks at fittings, water in the drain pan, proper seismic strapping (required in California), a temperature-and-pressure relief valve with a discharge pipe, and signs the unit was installed without a permit.
The rest of the checklist
- Water pressure: a $15 gauge on a hose bib should read roughly 40-80 psi; higher suggests a failed pressure regulator, which stresses every fixture in the house.
- Signs of leaks: stains on ceilings below bathrooms, warped cabinet floors, a musty crawl space, or a water meter that moves with everything off — the last one justifies professional leak detection.
- Drainage: fill sinks and tub, then release simultaneously; gurgling or slow multiple drains hints at venting or lateral issues.
- Permits on file: ask the city for permit history on the water heater, any remodel, and additions. Unpermitted bathroom additions are a common California surprise.
What it costs vs what it saves
A sewer scope plus a plumber's one-hour walkthrough might total $300-$700 all in. Against the realistic downside — a $10,000 lateral, a $10,000 repipe, a flooded ceiling six months after closing — it is one of the highest-leverage checks in the entire purchase, whether you are buying in Sacramento or San Diego.
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