November, 2008
Inspection News and Views from the American Society of Home Inspectors

Secrets of the Successful Home Inspector Revealed


“How did you know that about this house?” “Were you here before?” My clients ask me those questions because they want to understand how I know what I know. Most are intrigued when I tell them houses have secrets that an experienced home inspector can find and reveal. Many are interested in learning how I came to the conclusions recorded in my report, and I believe it’s worthwhile to satisfy their curiosity. My clients may have friends who will be buying houses in the future. The friends will need the services of a talented and knowledgeable home inspector — and who better than the inspector who revealed the secrets of the house?

The age of the house is only one of many factors to be considered when evaluating a system or component. But age is a good place to start for revealing secrets.

The following time line for residential electrical and plumbing systems is based on research conducted with the U.S. Patent Office and other sources tracking the development of materials used in housing across the country.


1880 to 1939 – Electrical wiring from this era is not considered safe for modern usage – due to age, brittle parts and insulation, corrosion, circuit overload and heat stress over time.

  • There is no grounding and outlets are not polarized for hot and neutral; hot and neutral wires are not color-coded for safety.
  • Minimal circuits are installed because electrical wiring was only for lighting.
  • The wiring is inadequate to handle more modern use as electrical appliances are added.
  • Edison-based fuses are used, which allow coins to be installed instead of fuses. Newer S-fuses need to be installed for proper ground protection.
  • Fused neutrals, reversed polarity wiring is unsafe.

1940 to 1969 – Electrical systems improve. 

  • Electrical systems still are not grounded and outlets are not grounded-type, but now are polarized.
  • Many wires are of poor quality, some plastic-coated, others are wire-covered cables.
  • Single-strand aluminum wiring used in some houses is unsafe

1967 to 1970­ – There were numerous problems with the wiring during these years due to wire overheating.

  • Multi-strand aluminum wiring, if properly sized for use, was considered safer.
  • Fuses still commonly used, but by this time some houses had breakers installed for ease of consumer use.
  • Breaker designs have had numerous failures due to non-tripping when needed.

1970 to 2000 – Electrical systems are safer.

  • Wiring is grounded and outlets are the grounded type.
  • More circuits are installed in houses to help support larger electrical demands by consumers.
  • Breakers are used to protect wiring in houses for common usage. Certain brands of breakers were no safer than the previous types because they would fail to trip.
  • GFCI breakers are designed to protect people from injury/death where water and ground faults could occur.

2001 to 2008 – Electrical systems are the safest yet.

  • Have GFCI breakers with interlock so that if incorrectly installed, the circuit will not work until wiring is repaired.
  • The wiring has grounded circuits on all wiring for safety.
  • More circuits with circuit protection with breaker protection are in use for safety.
  • There is AFCI-protection for bedroom circuits to protect from arc faults.


1880 to 1945 – Galvanized water pipe is used in houses, with lead pipes used for water mains to the house.  Galvanized pipe tends to rust with time, which will restrict water flow. Lead and other use-specific to regional areas pipes were used. Lead is now considered unsafe for everyone. 

1945 to 2008 – Copper pipe used in houses. Sometimes a combination of copper and galvanized pipes was used. Lack of dielectric unions cause electrolysis and pipe failure. Water lines routed under the concrete slab floor may have soldered joints that fail with age. Typically, pinholes can develop in copper piping due to water flow in pipe and chemical reactions to the copper.

1970 to 2008 – Non-metallic piping may have been used. The name of the pipe and date is printed on most non-metallic piping. 
PVC-White color used for cold water only.

  • CPVC-Tan color used for hot and cold water and has a diameter different from PVC piping that will not interchange without special fittings and approved glue.
  • Polybutylene pipe is grey in color and is used with compression rings of copper on fittings of plastic and copper. Some of this pipe is also a red- or blue-color plastic. This pipe and fittings has many problems; contact a plumber regarding replacement.
  • PEX-Is a cross-linked plastic pipe that is typically a milky-white color, although there are other colors, as well. This pipe may be used to replace other plumbing systems. 

PLUMBING: DWV (Drain Waste and Venting)

1880s to 1970s – Clay pipes were used for sewer drainage. This type of pipe allows roots to enter at joints which restricts the flow thru the line.

1880s to 1970s – Cast-iron sewer pipes may have been used. These pipes typically have lead and oakum at the joints.

1910s to 1950s – Orangeburg sewer pipe is a soft tar-, wood-fiber based product.

1970s to present 

  • ABS-Plastic pipe is used for sewer drainage. There have been issues relating to the use of the wrong type of glue
    and improper installation practices that have resulted in
    failure of the system.

  • PVC sewer pipe is used for sewer drainage.

This list of secrets related to the age of a house or its systems is non-inclusive and will differ by regions and locales of the country.

Watch for more classic home inspector secrets in future issues of the magazine.

Contributors: Bryck Guibor and Harris Breit are both ASHI Certified members (AKA: The Electrical Guys). They will be teaching at InspectionWorld 2009 in Orlando, Fla., in January 2009. Experts in electrical systems and defect recognition, they will present “Inspecting and Identifying Electrical Defects,” complete with photos of real defects so shocking you will hardly believe it. See you there!