Plumbing – Part 1 – What Makes up a House’s Plumbing System?


Part 1 in a Multi Part Series.

By Frank J. Delle Donne, Licensed Home Inspector

January 6, 2014

 About the author.  I am a NJ Licensed Home Inspector.  I am the owner and Senior Inspector at Regal Home Inspections, LLC.  I am a member of the New Jersey Association of Licensed Professional Home Inspectors (NJ-ALPHI) and the National Association of Certified Home Inspectors (NACHI).  The standards used to inspect your home’s systems are in accordance with New Jersey State laws, the American Society of Home Inspectors (ASHI) and NACHI Standards of Practice.  Regal Home Inspections, LLC can also test your house for Indoor Air Quality; Mold and Allergens.  Radon contamination is a big issue with homes in New Jersey.  Many parts of Monmouth County and areas around it are considered “High Radon Potential” by the NJ DEP. We are certified by the NJ DEP to perform Radon Testing.

We can also facilitate testing of septic systems and oil tanks; tank integrity and soil tests below ground.


Never perform plumbing work yourself unless you are a licensed plumber.  Nothing in this article suggests that you should attempt to make any repairs yourself.  Any attempt to make plumbing repairs or upgrades can result in significant water damage.  ALWAYS hire a licensed plumber to perform any work.   Poorly performed plumbing work can lead to water damage, ongoing leaks and other, related issues.


The plumbing system in a standard home inspection is extensive.  There are many aspects to a house’s plumbing systems, not just the pipes that carry water to the faucets and other appliances that use water.  The typical plumbing system in a home includes the pipes carrying cold and hot water but, not including the water heater as a separate plumbing element there are actually three (3) sets of piping in your home that are included in the plumbing inspection.

Before I get into a conversation about the plumbing systems let me point out that often times the vast majority of the plumbing systems are hidden behind finished walls, under floors and above finished ceilings.  Therefore we can actually see a very small portion of the plumbing and to the best extent possible, we make observations and come to conclusions about the entire system based upon what we can see.  In homes with extensively finished basements the amount of plumbing that is visible may be very, very little.

Plumbing Systems

In very general terms the, “plumbing” in a house consists of at least three sets of pipe, the water service entrance and water meter with its main shut off valve(s) and the water heater(s).  The appliances (sinks, toilets, tubs and showers) are also part of the plumbing system so overall the plumbing system in a house is extensive. And to make matters worse, if any one element has a defect which results in a drip, for example, you could have serious problems.  So let’s take a look at the components that comprise the plumbing in a house.

1) Supply Piping.  In a relatively modern home this is the copper piping.  The copper piping is usually ¾ or ½ inch in diameter.  It starts at the water meter (or pressure tank for a private well house) and carries the water to the isolation valves just before the appliance.  An example of an isolation valve is the valve behind the toilet bowl or under the sink.  In the case of the bowl, as you know, there is one valve as the toilet is served by cold water.  Under your sinks there is, of course, a hot and a cold isolation valve.  The copper pipes may also carry water to a hose bib that provides a convenient water valve outside your home.  These may, or may not have an isolation valve.

The supply piping is unique for a number of reasons but it is the only system that is under pressure.  Typical household water pressure is between 40psi and 60psi.  If your pressure is too low you will not get good water flow.  If it is too high, (at or above 80psi) you may have the potential to burst pipes, valves, gaskets and the like.  If you are concerned about your water pressure being too low, perform the following, simple test.  This may be an indication that your supply piping is in need of maintenance or replacement.

  1. Go to the highest bathroom in your house.  Usually it will be a full bath on the second floor.  If you have a ranch then any full bathroom will do.
  2. Turn on the sink valves and the tub and/or shower.  They should all be fully opened and running.
  3. Then, flush the toilet.  Watch the flow of water from the sink and tub/shower.  If the flow rates at the sink and tub/shower do not diminish, then you have adequate household pressure to operate your plumbing fixtures.  If they all slow down when you flush the bowl, you likely do not have adequate flow.

For a home built in 2014, the supply piping may not be made of metal.  There are a number of plastics used in current construction.  In homes built in the early 1900s and up to about 1940 you might actually find lead in the residential piping.  This should be replaced.   Galvanized steel was also used up to about the 1950s.  Galvanized steel rusts from the inside out and it is prone to becoming clogged inside the pipe from the rust build up.  Also, with this inside-out rusting the thinner areas where the pipe is threaded is  prone to leaking.   Brass may have been used in homes built in the early 1900s as well.

Copper has been in use since the middle 1900s.  It is durable, resistant to corrosion unlike the galvanized steel, and it’s relatively easy to work with. In summary, depending on the age of the home you may find different supply pipe materials, some of which should (must) be replaced.

2) Waste Piping.  The waste piping carries all the waste water and solids from the sink drains, washing machines and toilet bowls outside the house to the sewer system or to a private, septic system.  Modern waste piping is made of economical and easy to install PVC or a similar plastic material.  This is either white or the other forms of plastic piping may be black.  If it is visible, perhaps from an unfinished basement, you will see a series of feeder pipes running vertically into larger horizontal pipes and eventually the larger pipes will exit through the foundation wall in either a basement or perhaps in a crawl space.  This waste piping is not pressurized and for those sections that are not vertical, the slope should be relatively mild; about ¼ inch of slope per foot of horizontal pipe.

In older homes the waste piping may be cast iron.  Much heavier than modern materials and more difficult to handle and install.  There are all manners of interconnection devices so if a home improvement is being done you can remove sections of cast iron and replace it with PVC and they will interconnect very reliably.

3) Vent Piping.  Vent piping is the series of pipes that run (mainly) vertically and allows the waste water to flow properly.  To explain how the vent piping works and why it’s important think for a minute about a soda bottle.  If it’s full and you hold it upside down and then remove the cap the soda will gulp, gulp out and not evenly flow.  If you then poke a hole in the upper part of the inverted bottle the soda will pour out because the hole allows air to enter behind the soda.  The vent piping performs the same basic function as poking a hole in the soda bottle.  The vents allow air to follow the water as the water exits the house.  Without the vent piping the waste water would gulp, gulp, gulp its way out of your home.

The tops of the vent piping can usually be seen along the rear roof line of the home.  The vents penetrate the roof and allows air to flow behind the water.

These plumbing vents should NEVER terminate inside the attic or any living area.  Sewage gasses pass up through the vents and you do not want these gasses getting into the attic or any other living are of the house.  Vents should also not terminate near windows as the gasses could flow back into the house through the open window.  The gas needs to dilute quickly with the outside air and become benign.

So those are the three types of piping; Supply, waste and vent.

The entire plumbing system also consists of the water heater and the fixtures or appliances (sinks, bowls, etc.) that are connected to the supply and waste piping.

Water Heaters

Most water heaters are of the storage tank variety.  A few years ago instant-hot water heaters became popular and only made hot water when it was needed.  Personally, I believe the “instant” hot water is a slight misrepresentation.  The “instant” hot water maker begins to generate hot water as soon as a hot water valve is turned on but it could take a few minutes for the hot water to actually get to the faucet where the person is.  I don’t think that’s instantaneous as the name implies.

True, a tank hot water heater will maintain the desired hot water temperature in the tank whether the hot water is needed or not so this is somewhat inefficient.  The system I have is ideal in my opinion.  True, it is not as energy efficient as the “instant” water heater but in my case energy efficiency is not my primary concern.  And to tell you the truth, the simple convenience of being able to step into the shower 10 seconds after I turn on the water is also, not my primary objective.  In my house our water comes from a private well and the waste goes into a private septic.  If I didn’t have the system I have over the course of 1 year I would have pulled thousands of extra gallons of water from my well and dumped thousands of extra gallons of perfectly clean water down the septic system.  My primary goals are to be as efficient as possible with my water consumption and with my water disposal.  Conservatively I calculate that I have saved well over 12,000 gallons of water in the 6 years that I have had my hot water circulating system.  That’s 12,000+ fewer gallons pumped from the well and 12,000+ fewer gallons unnecessarily  poured into the septic.

A tank water heater with a re-circulating pump and a parallel hot water line is the best system for my needs.  I constantly have hot water circulating though my hot water pipes.  When none of the hot water valves is open the system is closed but constantly circulating hot water.  In the case of the master bath shower, 110 degree water is about 8 feet away from the shower head.  It’s like having a dedicated water heater a few feet away from every hot water valve.  In contrast, if I didn’t have the re-circulating pump the hot water from the tank would have to travel over 80 feet from the tank to the shower head.

So in this case, I am saving many gallons of water every day.  Yes it is costing me a little more in energy (natural gas) to keep the water hot but for my application, the system I have is what I need.

If you are interested in a hot water circulating pump for your house call Regal Home Inspections, LLC or email and I’ll put you in touch with the local plumber that installed mine.

When inspecting a home I look for a number of things associated with the water heater.  Not all are mentioned here but on an inspection the heater is thoroughly checked.   Let’s start with the make and serial number and capacity of the tank.  The first two data points will help indicate the year of manufacture.  If the heater is very old the buyer will be informed that the water heater may be nearing the end of its useful service life.

Where the pipes enter the tank on the top surface there is usually stamped into the metal the words, “Hot” and “Cold”.  Let’s make sure the heater is installed correctly!

The water heater may be electric but if it’s natural gas or oil I will check some other things including the exhaust vent piping and the burner area.

Of course I am looking for rust on the tank and indications that it may be leaking.   These are a few of the things that I look for on the water heating appliance within the overall household plumbing system.

Finally there are the appliances that use water that are considered part of the plumbing system.  The sinks, toilets, tubs, showers, clothes washing machine and dishwasher are parts of the plumbing system too.  Details on what I am looking for on these appliances will be covered in a future article.

If you are planning to sell your home, give Regal Home Inspections a call and hire us to perform a pre-listing inspection.  Here’s the logic.  If you allow Regal Home Inspections to perform an inspection before you list you can take care of some of the things up front.  You can use the inspection findings to make a list for the seller’s disclosure. More importantly, you can set the price with this knowledge.  Think about it…if you ignore the issues now, then when it comes time to execute the contract, the buyer’s home inspector will find these problems.  Then you are either negotiating away premium dollars to appease the buyer or you’re hiring an electrician (or a plumber, etc.) at the last minute to make corrections and that will cost you top dollar as well.  Deal with the issues you can and disclose the other issues.  That’s why at Regal Home Inspections we say, “Buy with confidence.  Sell with Pride.”

I would appreciate your comments about this article.  Please email your comments to