Plumbing: Quick Reference

Quick Reference Guide: Plumbing Materials

  1. Water Supply and Distribution
    1. Best Practices
    2. Types
      1. PEX
      2. Copper
      3. CPVC
      4. PVC
      5. Older Types (Galvanized and Polybutylene)
  2. Waste Lines
    1. Best Practices
    2. Types
      1. PVC
      2. ABS
      3. Older Types (Cast Iron, Vitrified Clay, Galvanized, Lead, Copper, Orangeburg)

Water Supply

Best Practices

Typical Sizes of Plumbing

Water service supply (from municipality or well) = 1″ (typically)
Water Distribution = 1/2″ (typically)

Minimum Spacing for Horizontal Supports of plumbing 1″ or less

Pex (1″ or less) = 32″
PVC= 36″
CPVC= 36″
Copper= 4′ and within 1′ of a change of direction

Water supply pipes should be installed 1.5″ behind the face of the stud or otherwise protected with a shield plate to prevent leaks and flooding.  Underground water supply pipes should be buried below the frost line (16″ in our area) with a 14 gauge ‘tracer’ line to help locate the pipe.  Water supply pipes should be rated for household use that can withstand pressure of 80psi or more and temperatures of 120F or more.


  • PEX

    • PEX is one of the most commonly used water distribution plumbing materials in use today.  PEX is preferred by plumbers and installers because of its flexibility, affordability and ease of installation.  PEX does not corrode and is less likely to burst during freeze events than metal pipes.  PEX has proven to be a durable and reliable material as long it is installed correctly (an exception are the Q-PEX fittings)
      • Type A PEX is manufactured by Uponor or Wirsbo.  Type A has better flexibility,  and less flow restriction problems at the fittings than Type B.  This type is also more expensive and less commonly available in our area.
      • Type B PEX manufactured by Zurn is more commonly used and available in our area.
    • Dezincification of Brass Fittings (1990s-2013): This concern has to do with the connectors or fittings and not the pipes themselves.  Between the 1990s and 2013 some manufacturers were producing sub-standard brass fittings that are known for dezincification, corrosion, and leaks.  Zurn, one of the major manufacturers of the fittings, settled a class action law-suit in 2013– their brass fittings are labeled ‘Q-PEX’ or with the number ‘F-1807’.  As a home inspector I can confirm that this is a very common issue and a number of my clients have had to replace their fittings and/or most of their pipes (sometimes after only 10-20 years).  I consider the de-zincification problems of inferior PEX brass fittings to be more serious than the presence of polybutylene pipes in the home (which is also no longer installed because of a class action lawsuit)
    • Flow Restriction at Fittings:  Because Type B (Zurn) fittings utilize insert type fittings they can noticeably reduce the flow and should be up-sized as needed.
  • Copper

    • Copper piping is still commonly used today and is known for its reliability and longevity.  Copper can handle very high temperatures and may be the longest lasting of all plumbing distribution types.  According to some Copper piping typically requires more specialized tools and skills than PEX to install or repair.  Special fittings, like SharkBite, may allow a homeowner to do their own repairs however best practice is to hire a licensed plumber.
    • Acidification: Copper is prone to damage from highly acidic water.  Copper piping is made for different applications and has various wall thicknesses (Type K, L & M)- thinner piping (like Type M) is more prone to acidification and leaks over time.
    • Freezing/Bursting: Copper is more prone to freezing/bursting than PEX which is why steps should be taken to insulate or protect copper piping in un-heated areas in regions that have freezing temperatures.
  • CPVC

    • CPVC has proven to be a reliable and durable material when properly installed.  CPVC can withstand hot temperatures up to 200F (93C) as opposed to 140F (60C) for PVC however most residential water heaters should not be set above 120F (48C).  For whatever reason (price and ease of installation?) CPVC has fallen out of favor with plumbers and installers over the recent decades and is less common than other materials.
  • PVC

    • PVC has proven to be a very reliable and durable material when properly installed.  PVC is still very commonly used for water distribution however PEX has become increasingly popular because of its flexibility, price and ease of install.
  • Older Types

    • Galvanized (1880s-1960s)
      • Galvanized pipes have not been installed since around 1960 and have about a 50 year life expectancy which means all galvanized distribution pipes in older homes are now beyond their life expectancy and are overdue for replacement.
        • Replacing Underground Galvanized pipes (from street or municipality): when the underground pipe from the house to the water source (well or municipality) is galvanized this could present a potentially difficult and expensive project to the homeowner that will require trenching and navigating through hard surfaces, landscaping, additions, etc…
        • Replacing Galvanized pipes within the home: Replacing galvanized pipes in unfinished crawl spaces and basements may be straight forward but less accessible areas like finished walls and ceilings will increase replacement costs.  In some cases hidden sections of galvanized plumbing are still present in homes.
        • Replacing Short Sections of Galvanized (appliances and fixtures):  Sometimes plumbers will use short sections of galvanized pipes at water heaters, well pressure equipment and other plumbing fixtures when they know that the short sections of pipe will be replaced when the fixture or appliance is replaced (typically 25 years).  As a home inspector I do not love this practice but it is allowed and it should not be an issue unless it is left in place for 40 years or longer.
      • Corrosion: Galvanized pipes are known for de-zincification, corrosion, leaks and flow restriction issues.
      • No longer installed:  Except for occasional short sections at plumbing fixtures and appliances galvanized pipes are no longer used for distribution plumbing in the own because of their known issues
    • Polybutylene (1978-1997)
      • Dis-continued: There was a class action law suit in 1995 due to leaks and damaged pipes and now Polybutylene is no longer installed in homes.
      • Becomes Brittle: Polybutylene pipes are subject to damage from chemicals over time, especially chlorine used to treat municipal water.  There may be less of a concern if the water is supplied by a well.
      • Incorrect Transition fittings: Because polybutylene is similar in size to PEX many homeowners and un-licensed professionals (and some licensed ones) have used the incorrect type fitting when transitioning from one material to another.  It should always be verified that the correct Polybutylene to PEX fitting is used (or other material) to prevent leaks over the long-term
      • The chemical reaction occurs inside the pipe and therefore the extend of the damage is hidden of difficult to determine.  Leaks or failure may develop suddenly and without warning.
      • In my home inspection career I’ve seen more active leaks and issues related to sub-standard brass PEX fittings than I have polybutylene.

Waste or Drain Lines

Best Practices

Waste line pipes should be gradually sloped downward to ensure waste (typically 1/4″ per foot or 1/8″ for 3″ and larger pipes).  PVC and ABS drain line pipes should be supported every 4′.  Every house should have at least one vent exit through the roof.  Every plumbing fixture should have a trap and a venting system to help prevent the escape of sewer gases and to ensure proper drainage.

Typical Sizes of Plumbing

Main Waste Line = 3″ for smaller homes and 4″ for larger
Toilet = 3″ or 4″
Shower Waste Line = 2″
Sink = 1-1/4″ to 1-1/2″


  • PVC

    • PVC is the most commonly used drain line material within residences and has proven to be a durable material over time.
    • PVC is more flexible and muffles sound better which is why it is used within the home more than ABS
      • Schedule 40 (Most residential applications)
      • Schedule 80 (Commercial or Industrial applications)
      • Schedule PR160 (Landscaping – French drains and downspout sub-surface drains)
  • ABS
        • Similar to PVC, ABS is still commonly used today and has proven to be a durable material over time
        • ABS is slightly stronger and resists impact better than PVC which is why it is commonly used in underground applications.
  • Older Types
    • Cast Iron
      • Cast iron was the best of the older materials and is known for its durability
      • Since Cast Iron drain lines have not been installed since around 1975, much of it is older and beyond its expected service life
      • Cast iron drain lines have a service life of between 50 and 100 years
      • Acidic sewage and humid environments in crawl spaces can corrosion and leaks over the long-term
      • Cast iron is more difficult to repair/replace than PVC/ABS.  Specialized tools and techniques are often required for a successful repair.
    • Vitrified Clay (terra cotta)
      • Vitrified clay is a material that has been used for millennia and is still commonly used today for underground applications.
      • Vitrified clay is acid, corrosion and abrasion resistant
      • Vitrified clay is more difficult to install and repair than PVC/ABS
      • Older Vitrified clay materials used in sewer line applications are prone to leak at connections, have low tensile strength, and are vulnerable to root damage.
    • Galvanized
      • Galvanized drain lines have a 50 year life expectancy
      • Galvanized drain lines for residential applications typically have not been installed since the 1960s
      • Most or all galvanized drain lines present in homes are now beyond their expected service life and should be replaced soon.
      • Galvanized drain lines are prone to corrosion from the inside (dezincification) and can cause leaks, floods, water damage and failure.
    • Lead
      • Commonly used up until the 1950s
      • Lead pipes were banned by congress in 1986 (lead drain lines were allowed to stay in place)
      • Still seen today in homes but typically in drain lines only (does not have the health concern that lead supply pipes do)
      • Corrosion resistant and malleable
      • Toxic to touch.  Can cause lead poisoning if not handled carefully.
    • Copper
      • Copper drain pipes are sometimes seen in homes built before 1970
      • Copper drain lines are prone to acidic corrosion caused by sewage
      • Most copper drain lines are beyond their service life and should be replaced soon
    • Orangeburg
      • Orangeburg pipes were typically used for drain line system between 1950 and 1970
      • Orangeburg pipes were made from wood pulp and tar
      • Orangeburg pipes are known for the lack of strength and for their propensity to compress/deteriorate and to fail catastrophically
      • Orangeburg is no longer manufactured or considered an acceptable plumbing material
      • Orangeburg pipes are now beyond their expected service life and should be replaced

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