While the exact cause is uncertain, it is believed that the oxidants (such as chlorine) in public water systems react with the plastic, causing it to flake and become brittle. As the integrity of the piping deteriorates, tiny fractures develop, which can expand over time and cause a sudden failure of the pipe and resulting water damage.

   Galvanized steel is another type of pipe material that is no longer installed for water supply piping, although still available and used for repairs of existing systems. It was often used for water supply piping in homes until the early 1970s, but not used today because corrosion problems limit it’s useful lifespan to between 40 and, at best, 50 years. Rust-corrosion accumulates inside the pipe and causes a plumbing version of arteriosclerosis, with the gradual hardening-of-the-arteries narrowing the diameter of the pipe in horizontal runs to the size of a soda-straw in places. Essentially, it rusts from the inside out. This restricts the flow of water to faucets and showers and, eventually, the corrosion causes the pipe to spring leaks--usually the first place being in the ground under the home’s concrete floor slab, or near the water heater due to an electrolytic reaction to copper fittings speeding up the corrosion.

The photo below shows the end of an abandoned section of galvanized pipe in a laundry room wall, where it was cut-off at the juncture with a washing machine faucet. As you can see, the water flow was severely reduced from the buildup of rusty crud in the pipe. Surrounding it is the cream-color plastic pipe that replaced it, called CPVC.

   Both PB and galvanized pipe may be problematic when you apply for homeowner’s insurance for an older home. Some companies will not write a policy for homes with PB or galvanized, and others require a licensed plumber to certify that the pipe system is in satisfactory condition.

2) Pipe material and fixtures that are at the end of their serviceable lifespan - Every component of a home has an average lifespan. Sometimes it will last longer than the average and, then again, occasionally it fails sooner. Here’s some plumbing life expectancies:


          Copper - 60 to 80 years

          Galvanized Steel - 40 to 50 years

          CPVC and PVC - 40 to 50 years

          PEX - 40 years


          Cast Iron - 50 to 65 years

          Galvanized Steel - 40 to 60 years

          Copper - 60 to 80 years

          PVC - 50 to 70 years


          Water Heaters - 10 to 20 years

          Faucets - 15 to 25 years

          Sinks, Tubs, Toilets - 40 to 80 years

          Shut-off Valves - 20 years

   Advanced deterioration of plumbing is easy to spot. The photo at the top of this blog is old galvanized steel pipe that is clearly showing its age, with heavy corrosion and beginning to leak. In other instances, the piping or fixture may look younger that its known age; but, as plumbing approaches the the end of it’s estimated lifespan, you should expect replacement soon. Water shut-off valves have a rating of 20 years because they tend to be frozen in the open position at that age. Your home inspector will note any plumbing that is visibly deteriorated, but inspectors do not test shut-off valves.

3) Defective repairs made by the homeowner or a handyman - Just because a professional plumber did not do all the plumbing work in a home does not automatically mean that it is bad. However, we practically never see incorrect plumbing installation by a licensed plumber. Sink drain configurations that would make even Rube Goldberg laugh occasionally happen when a non-professional tackles a home renovation project.  Traps installed backwards or doubled-up, poorly secured pipes, unvented drains, and unsafe water heaters are common. To read more about water heater installation, see our blog “What are the most common installation problems with water heater replacement.”

   Also, accordion-type piping is a sure sign of amateur plumbing work.  The photo below shows a homeowner’s sink drain repair using accordion pipe as a tailpiece, connected to three P-traps in a configuration that is absolutely guaranteed to clog.

Although home improvement and hardware stores sell the stuff and it makes easy work of connecting two pipes that are not aligned, the pipe is not rated for installation by any plumbing codes and the ridges collect hair and debris. Here again, your home inspector can help you sort through any haphazard plumbing repairs and determine what needs to be redone.

    Because the age and condition of an older home’s plumbing components do not always correspond with the age of the house or a date of renovation, a careful evaluation of the system is always a sensible part of the due diligence necessary in buying a home.

• • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • •

   To read about issues related to homes of a specific earlier decade or type of house, visit one of these blog posts:

What are the common problems to look for when buying a 1950s house?

  1. What are the common problems to look for when buying a 1960s home?

  2. What are the common problems to look for when buying a 1970s home?

  3. What are the common problems to look for when buying a 1980s house?

  4. What problems should I look for when buying a country house or rural property?

  5. What problems should I look when when buying a house that has been moved?

  6. What problems should I look for when buying a house that has been vacant or abandoned?

  7. What are the most common problems with older mobile homes?

  8. What should I look for when buying a “flipper” house?

  9. What should I look for when buying a former rental house?

While we hope you find this series of articles about home inspection helpful, they should not be considered an alternative to an actual home inspection by a local inspector. Also, construction standards vary in different parts of the country and it is possible that important issues related to your area may not be covered here. ©2015 - McGarry and Madsen Inspection.

NOTE: These life expectancies are based on data provided by InterNACHI, NAHB, and our own professional experience.

Because of the numerous variables that can affect a lifespan, they should be used as rough guidelines only,

and not relied upon as a warranty or guarantee of future performance.


How to Look

at a House

A blog with answers
to your questions about

More Blog Posts about Plumbing:

  1. Should I upgrade to a tankless water heater?

  2. Why does my well pump turn on and off every time I use water?

  3. How old is that water heater?

  4. My air conditioner won’t turn on. What’s wrong?

  5. Should I wrap the water heater with an insulation blanket?

  6. What’s the powdery crust on the pipe connections at the water heater?

  7. Do you check the plumbing under the floor slab?

  8. Do I have polybutylene pipe? Why is it a problem?

  9. What is causing a foggy haze on my windows?

  10. What is that big thing in the toilet tank?

  11. How do I remove cigarette odor in a house?

  12. What is the difference between water service pipe and water supply pipe?

  13. What’s the flip-up handle on the water heater for?

  14. How come the water has a rotten-egg smell in some empty houses?

  15. My well water test came back positive for bacteria. What should I do?

  16. Do you test the well water?

  17. What is the difference between a regular water heater and a power vent water heater?

  18. How can I tell what type of plumbing pipe I have?

  19. How do you test a shower pan for leaks?

  20. Why is my water heater making strange (rumbling, gurgling, knocking or banging) noises?

  21. What is that pipe sticking out of the ground in the yard?

  22. Why are rubber washing machine hoses a safety risk?

  23. What are the common problems to look for when buying a 1980s house?

  24. What is a dielectric union?

  25. What is a heat pump water heater?

  26. What are the common problems to look for when the plumbing has been replaced in a house?

  27. What is the average life expectancy of copper pipe?

  28. Why can’t PVC pipe be used for water pipe inside a house?

  29. What is an auto vent, air admittance valve, or check vent?

  30. Why is a European-style bottle trap not approved by the plumbing codes in the U.S.?

  31. What are the most common problems with wall/window air conditioners?

  32. What is an FVIR water heater?

  33. What is difference between a single element and dual element electric water heater?

  34. What are the requirements for installing a gas appliance connector?

  35. What is an escutcheon plate?

  36. What is the loose wire sticking out of the ground under the gas meter for?

  37. Is the hot water faucet handle required to be on the left?

  38. Should I seal the washing machine drain hose to the standpipe?

  39. How do you find a broken water pipe leak under the floor slab?

  40. What is the minimum and maximum slope of the trap arm of a plumbing drain?

Polybutylene Pipe

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