Plumbing Supply Pipes

Plumbing Supply

One area of a home system that often confuses people is plumbing. Plumbing has two different systems, the supply of water into a house, and the pipes that carry water and waste away from the house. Much like a person drinks and expels liquid through different means, so does a house.

The confusing is when people discuss plumbing, they often only refer to one part of the system, without taking the other parts of the entire system into account.

For example, when someone says the plumbing was redone with all coper, they are only referring to the supply of water into the house, as a copper re-pipe job has nothing to do with the pipes that carry water and waste away from the home.

Supply: Bringing the water in

First, let’s look at the supply pipes. We will discuss drain pipes in a separate article. There is one main pipe that goes from the utility water meter up to the house. This pipe is almost always underground and not visible. From this point, there is usually a main water shutoff, and often a water pressure regulator. After this, the water goes to the supply system that carries water to each individual faucet.

Here are the materials often used a supply pipes

Galvanized Steel

Galvanized with corrosion

There was once a time when galvanized steel was the preferred material for water supply pipes, as it didn’t have the health hazards of lead, and was easy to install. However, over time, it was discovered that galvanized steel corrodes over a period of several decades, and is no longer used. Steel was phased out in the 1960′ and stopped being used in the early 1970′ s as a water supply pipe. Many older homes still have galvanized steel. Even houses without steel often have steel connectors or parts installed by well-meaning people who don’t understand that steel can and will corrode over time. Galvanized steel also remained popular as an irrigation pipe material long after it stopped being used in houses.


Copper to Galvanized
Copper to Galvanized

Copper became the preferred method of water supply pipes in the 1960’s, and eventually completely replaced steel as the primary material for supply pipes. The main downside of copper is cost. Copper prices have fluctuated greatly over the decades. Copper also is more labor-intensive to install, again adding to the price. One problem builders have is people stealing copper from building sites when the price is high.

While copper, in general, will not corrode, that is only if it only it remains free from contact with other metals. Any cross-connecting with galvanized steel pipes or contact with nails, staples, or other metals used in buildings can cause electrolysis, which will corrode copper. Copper can also age from minerals and chemicals often found in normal tap water, leading to copper eventually develop pinhole leaks.


Polyvinyl chloride pipes, better known as PVC, can be used as water supply pipes. however, PVC is ONLY rated for cold water, so it is rarely used inside a house, though it may be found from the utility to the house, and is popular with irrigation and pool plumbing, where hot water is not used. PVC can break down from sun exposer, which is why it is usually buried and not visible. Any exposed PVC should be painted, as paint acts like a sunscreen to protect the pipe from sun damage.


Chlorinated Poly Vinyl Chloride, CPVC is similar to PVC, but with a different chemical makeup, it is approved for hot water use.

Despite it being approved for a water supply pipe, the use of CPVC is rare.  Some plumbers will say CPVC is too unreliable for water supply pipes, but the only known cases of CVPC failure are in Florida. We usually only see it in some parts of Santa Clarita.


Pex Plumbing
Pex Plumbing

Cross-linked polyethylene, better known as PEX is becoming the new standard for water supply pipes. It has been in use in Europe for decades. It was approved for use across California in 2009, though it was approved in Santa Clarita and some other areas well before then. New construction and remodels are increasing using PEX over copper because PEX is much cheaper than copper, much easier to install, and unlike copper, no one will steal it when a house is being built. PEX comes in several colors, which makes it easy to keep track of hot vs cold, though the colors having nothing to do with the actual function of the pipes.

The only downside of PEX is it not rated to be in direct contact with sunlight. It can not be used outside, or in any areas where it can be exposed to sunlight.


Lead was a common pipe used for centuries due to it being easy to work with. Lead pipes are now considered a health hazard. We almost never see actual lead pipes anymore. Though some may still exist in areas like Pasadena or areas close to downtown where many houses were built before any modern safety standards were in effect. Technically, lead can be found in the solder of copper pipes installed prior to 1986, though the presence or absence of lead in the solder is not visible to the naked eye.

Polybutylene was a short-lived plastic-type pipe developed in the late 1970s which was found to fail under pressure. Though across America it was installed in millions of homes, here in Southern California we tend only ever see polybutylene is mobile homes built in the late 1970s or 1980s.

At IM Home Inspections, your inspector will attempt to identify the visible portion of the supply pipes of your house. Additional materials may or may not exist behind walls, underground, or otherwise in additional areas that are not visible.

To book your inspection today, call 818-298-3405 or book online here.