Behind every drywall panel is a network of pipes doing quiet work until something fails. Knowing the types of pipes in your house, what they handle, and when to replace them saves you from emergency plumber bills and flood-damaged floors. Older homes often mix five or six pipe materials from decades of partial upgrades, which is why a casual remodel can turn into a full repipe fast. This guide covers supply lines, drain pipes, and the main gas and vent systems, with realistic costs and red flags for each.
- PEX: The Modern Supply Standard
- Copper: The Traditional Workhorse
- PVC: For Drains and Irrigation
- CPVC: The Hot Water PVC
- Galvanized Steel: Time to Replace
- Cast Iron: Old Drain Lines
- Polybutylene: The Pipe to Remove
- Gas Lines: Black Iron and CSST
- Which Pipes Are Where in Your Home
- Budgeting for Pipe Work
PEX: The Modern Supply Standard
PEX (cross-linked polyethylene) has become the default for new construction and most remodels. Flexible tubing comes in 100 foot coils, snakes through framing with fewer fittings, and resists freeze bursts better than copper because it expands.
- Cost: $0.50 to $2 per foot for tubing, $2 to $4 per fitting
- Lifespan: 50 years or more when protected from UV
- Best uses: Hot and cold water supply lines throughout the home
- Watch out: Keep at least 12 inches away from recessed lights and gas flue pipes; UV damages it within months
PEX comes in red, blue, and white to color-code hot, cold, and general runs. Type A is the most flexible and forgiving for DIYers; Type B is cheaper and more common in big box stores.
Copper: The Traditional Workhorse
Copper has been the gold standard for 70 years. It handles heat, pressure, and outdoor temperature swings without degrading. Type L copper is the residential default, while thinner Type M is often used in low-pressure repairs.
The downsides are price and labor. Copper runs $2 to $8 per foot and requires soldered joints or pricier press fittings. A repipe in copper often costs 50 percent more than PEX, and copper thieves target homes under construction for the scrap value.
PVC: For Drains and Irrigation
White PVC pipe handles drain, waste, and vent (DWV) applications in nearly every modern home. Schedule 40 is the standard residential grade. It never rusts, solvent welds cleanly, and costs only $0.50 to $1.50 per foot for common 1.5 to 4 inch sizes.
PVC cannot handle hot water supply lines above about 140 degrees F, which is why it stays confined to drains and cold irrigation. Exposed outdoor runs need paint or insulation to block UV degradation.
CPVC: The Hot Water PVC
CPVC (chlorinated polyvinyl chloride) is PVC’s heat-tolerant cousin, rated for 180 degrees F. It was popular in the 1980s and 1990s for hot water supply lines before PEX dominated. You can still buy it for around $0.75 per foot, but most plumbers now prefer PEX because CPVC turns brittle with age.
If your home has CPVC supply lines that are 25+ years old, factor a repipe into your next major remodel. The plastic becomes glassy and shatters under light pressure, leading to ceiling leaks that often catch homeowners off guard.
Galvanized Steel: Time to Replace
Galvanized pipe dominated residential supply lines from 1900 through the 1960s. Inside, zinc coating reacts with water over decades, causing mineral buildup that chokes flow and releases rust into the water. You can spot it by the dull silver-gray exterior and threaded joints.
If you have galvanized supply lines, expect:
- Brown water after the system sits unused
- Weak flow at upper-floor fixtures
- Pinhole leaks at threaded joints
- Lead contamination risk if lead solder or lead service lines are in the mix
Budget for full replacement with PEX or copper. Patchwork repairs rarely last more than a year before the next joint fails.
Cast Iron: Old Drain Lines
Cast iron drains remain in homes built before 1975. When intact, they quiet drain noise better than PVC and handle decades of abuse. The issue is rust and scale. After 50 to 75 years, iron drains rot from the inside, develop pinholes at the bottom, and eventually collapse.
A camera inspection ($250 to $400) tells you the shape of your drains. Replace failing sections with PVC using no-hub fernco couplings, which take a day per bathroom for a competent plumber.
Polybutylene: The Pipe to Remove
If your home was built between 1978 and 1995, check for gray polybutylene (Poly-B) supply lines. Class-action settlements paid out on this material for good reason: it reacts with chlorine in municipal water and fails without warning.
Poly-B is the only common residential pipe that insurance companies sometimes refuse to cover. Replacement is not optional if you see it. A typical full repipe with PEX runs $4,500 to $10,000 depending on home size.
Gas Lines: Black Iron and CSST
Natural gas and propane use different pipe than water. Traditional runs use threaded black iron pipe, painted black or primed gray. It is strong, rigid, and non-combustible.
Newer installations use corrugated stainless steel tubing (CSST), flexible yellow or black tubing that snakes through framing. CSST requires proper bonding to a grounding electrode to prevent lightning strikes from arcing through the line, an often-missed detail in older installs.
Which Pipes Are Where in Your Home
A typical 2010+ build uses this stack: PEX supply lines, PVC drain and vent, black iron or CSST gas, and PEX or copper for the main service. Homes built in the 1950s through 1970s often have copper supply, cast iron drains, and galvanized branch lines. Pre-1950 homes can be a patchwork of lead, galvanized, and early cast iron that deserves a full assessment.
Walk your basement with a flashlight and photograph the visible sections. The exterior color, joint style, and diameter give you a starting map. A plumber charging $125 for a consult can identify the rest in an hour and flag anything that belongs in the replace-soon category.
Budgeting for Pipe Work
For planning purposes, small repairs run $200 to $600. A single fixture replacement runs $400 to $900. A full repipe of a 2,000 square foot home runs $4,500 to $12,000 depending on wall access and pipe material. Drain replacements cost more than supply because the pipe sizes are larger and the pitch math matters. Knowing the types of pipes in your walls before you remodel prevents a surprise that doubles the project scope mid-demolition.
