Plumbing Inspection Guide: Pipe Materials, Red Flags & Repair Costs
The pipe materials in a home are largely determined by when it was built. Knowing which pipes are present — and what problems each material is prone to — can mean the difference between a routine inspection and a $4,000–$15,000 repiping project.
Pipe Materials by Era: Risk Reference Table
Home inspectors identify pipe materials by visual inspection of exposed pipes in basements, crawl spaces, utility rooms, and under sinks. The construction era of the home narrows down which materials are most likely present.
| Material | Common Era | Typical Lifespan | Risk Level | Notes |
|---|---|---|---|---|
| Lead pipe | Pre-1930 | Indefinite (toxic) | Critical | Health hazard; not permitted; replace immediately if found |
| Galvanized steel | Pre-1960 | 40–70 years | High | Corrodes from inside; restricted flow; common cause of low pressure |
| Cast iron (drain) | Pre-1980 | 50–100 years | Low–Moderate | Durable; can rust through from inside with age; check at joints |
| Copper (supply) | 1960–present | 50–70 years | Low | Industry standard; pinhole leaks possible in aggressive water chemistry |
| Polybutylene (PB) | 1978–1995 | Unpredictable | High | Recalls; fails at fittings; replace; insurance issues |
| ABS (drain) | 1970s–present | 50–100 years | Low | Black plastic; durable; check for improper cementing at joints |
| PVC (drain) | 1980s–present | 50–100 years | Low | White plastic; standard modern drain pipe |
| CPVC (supply) | 1980s–present | 50–75 years | Low–Moderate | Cream-colored rigid plastic; can become brittle with age |
| PEX (supply) | 1990s–present | 50+ years | Low | Flexible; freeze-resistant; current preferred material for repiping |
Use our home age hazard checker to see which plumbing materials and other hazards are typical for your home's construction decade.
What Inspectors Test During a Plumbing Evaluation
Home inspectors run specific tests on plumbing systems during the inspection. These are functional evaluations, not pressure tests or video scoping — those require specialty equipment.
Inspectors measure supply water pressure. Normal range is 40–80 psi. Below 40 psi indicates flow restriction (common with galvanized pipes) or supply issues. Above 80 psi can damage appliances and indicate a missing or failed pressure regulator.
Every sink, tub, and shower is run to verify hot and cold water supply, check flow rate, and observe drain speed.
Slow drains are noted. Multiple slow drains simultaneously can indicate main line issues; isolated slow drains are typically local clogs.
Each toilet is flushed and observed for complete flush, fill time, and running (indicates flapper or fill valve failure).
Exposed pipes in basements, crawl spaces, utility areas, and under sinks are checked for corrosion, leaks, improper materials, and unsupported spans.
Main water shut-off and individual fixture shut-offs are noted. Stuck or leaking shut-offs should be replaced before closing.
Age, condition, temperature setting, TPR valve and relief discharge pipe, flue condition (gas), anode rod access, and whether the unit is strapped (seismic zones).
Exterior hose connections and irrigation shut-offs are checked. Frost-free hose bibs are the standard in freezing climates.
Polybutylene Pipe: The Highest-Risk Plumbing Defect
Polybutylene supply pipe was installed in an estimated 6–10 million homes built between 1978 and 1995. It is the single most significant plumbing defect a home inspector can identify.
- - Gray or blue-gray flexible plastic pipe (also occasionally white or black outdoors)
- - Marked "PB2110" on the pipe surface
- - Typically 1/2 inch to 1 inch diameter for supply lines
- - Connects with plastic or metal crimp-style fittings (the fittings are also a failure point)
- - Common in homes built in the Southeast, Pacific Northwest, and Sun Belt during this era
Chlorine and other oxidants in municipal water supplies degrade polybutylene from the inside out. The pipe becomes micro-fractured and eventually fails at fittings or along the pipe itself, often with little warning.
Many homeowner's insurance companies refuse to cover homes with polybutylene supply pipes or charge a significant surcharge. Confirm with your insurer before purchasing.
Full repiping with PEX or copper is the only reliable solution. Partial replacement still leaves degraded pipe in the system. Negotiate a repiping credit or require replacement before close.
Galvanized Steel Pipe: The Other Era-Specific Problem
Galvanized steel supply pipe was common in homes built before 1960. It corrodes from the inside, progressively reducing water flow and eventually failing. If a pre-1960 home still has its original galvanized supply pipes, repiping is likely needed.
- - Low water pressure throughout the home
- - Brown or rust-colored water when first run
- - Visible rust and mineral deposits on pipe exterior
- - Frequent leaks at joints and fittings
- - Uneven pressure between fixtures
- - Full repiping with PEX or copper: $4,000–$15,000
- - Pipe lining (epoxy coating): limited application
- - Partial replacement increases until full repipe is done
- - Cast iron drain lines often replaced simultaneously
- - PEX is preferred for most repiping projects today
Water Heater: Age, Condition, and When to Replace
The water heater is one of the most frequently flagged items in plumbing inspections. Tank-type water heaters have a well-documented lifespan and visible failure indicators.
Tank-type gas or electric water heaters typically last 8–12 years. Tankless (on-demand) units last 15–20 years. The manufacture date is encoded in the serial number — inspectors know how to read it, and you can look it up by brand on manufacturer websites.
Rust-colored water from hot taps, audible rumbling or popping during heating cycles (sediment buildup), visible rust or moisture at the base of the tank, or a tank that has already exceeded its expected lifespan.
The temperature-pressure relief valve is a critical safety device. It must have a proper discharge pipe that terminates near the floor or outside. An improperly installed TPR valve or missing discharge pipe is flagged as a safety deficiency.
Standard 40-50 gallon tank-type water heater replacement: $1,000–$1,800 installed. High-efficiency heat pump water heater: $1,500–$3,500. Tankless (on-demand) gas: $1,800–$3,500 installed.
Supply vs. Drain Lines: Different Problems, Different Costs
Supply lines (under pressure) and drain lines (gravity-fed) fail differently and have different repair costs. Both are evaluated during a home inspection.
- - Active leaks immediately visible or behind walls
- - Low pressure from corroded galvanized pipe
- - Polybutylene deterioration risk
- - Freeze damage in poorly insulated spaces
- - Repiping cost: $4,000–$15,000
- - Slow drains from buildup or root intrusion
- - Cast iron corrosion in 50+ year old homes
- - Inadequate slope causing standing water
- - Main sewer line issues (requires sewer scope add-on)
- - Drain line replacement: $1,500–$8,000
Note: A standard home inspection does not include a sewer scope. This is a specialty add-on that involves a camera in the main sewer lateral. It is strongly recommended for any home over 20 years old — see our full inspection checklist.
Frequently Asked Questions
A home built in 1975 could have copper supply lines (most likely), galvanized steel supply lines (in older sections or if partially updated), or polybutylene pipes if the plumbing was updated between 1978 and 1995. Drain lines are likely cast iron in main stacks with ABS or PVC branch lines. If the home was built or replumbed between 1978 and 1995, polybutylene (gray plastic pipe) may be present — this is a significant concern. Your home inspector will identify the pipe material during the inspection.
Repiping a house with PEX or copper typically costs $4,000–$15,000 depending on home size, pipe material selected, access requirements, and local labor rates. A small 1,000 sq ft home may repipe for $4,000–$6,000; a larger two-story home can run $10,000–$15,000. Copper repiping is more expensive than PEX. Homes with slab foundations cost more to repipe because accessing under-slab lines requires concrete cutting.
Polybutylene (PB) pipe is a gray plastic pipe used in residential plumbing from approximately 1978 to 1995. It was recalled following a class action settlement (Cox v. Shell Oil) due to a widespread tendency to become brittle and fail at fittings. The pipe degrades when exposed to chlorinated water, causing micro-fractures that eventually rupture. Polybutylene is identifiable by its gray or blue-gray color and is typically marked 'PB2110' on the pipe. Its presence in a home requires evaluation and replacement planning. Many insurance companies will not cover homes with active polybutylene supply lines.