What Is a Water Supply Line and What Does It Do?

Most homeowners understand the basics of how home plumbing works. Turn on the faucet, and you have water. Whatever you put in a sink eventually goes down the drain.

It’s not until there’s a water problem that you wish you knew just a little bit more about your water supply line and how it works. Instead of wasting time troubleshooting online—and going down too many rabbit holes—we’ve put together everything you need to know about how your plumbing system delivers fresh water to your home. Take a few minutes and explore one of the most critical systems in your home.

What Is Inside Your Plumbing System?

Plumbing systems may seem complicated, but if you look at the schematic for a residential system, it’s relatively simple. We say plumbing system, but it’s easier to think of plumbing as two separate yet connected systems. One system brings fresh, clean water to your home. The other removes dirty water. Within each of these systems, you’ll find sub-systems. In the part of the plumbing system that delivers fresh water, you’ll find water supply lines. The plumbing system removes dirty water via waste pipes. With dirty water comes odors. The system relies on vent pipes to direct odor-causing sewer gasses to the outside of your home. Fixtures like sinks, showers, and toilets connect the fresh and dirty water systems. Water-using appliances—dishwashers and washing machines—also work as connections.

What Is a Water Supply Line and What Does It Do?

The work of a water supply line isn’t restricted to supplying water to the fixtures inside your home. Water supply lines also deliver water to outside fixtures, so you can use a garden hose or an irrigation system. If you were to observe the plumbers installing a new residential system, you’d see two types of water supply lines. One manages cold water, while the other handles hot water once it leaves the water heater. Water supply lines come in various colors, including red, blue, and gray. You may also notice braided stainless steel supply lines depending on the application. Every home plumbing system connects to a main water supply line. It’s often called a water service line. These lines wear out and may cause problems as they age. Being proactive and inspecting the lines before they break down can save money and time.

Main Water Service Lines

Main water service lines enter a home at ground level or below, depending on your geographic location. If you live in a warm weather zone, you can usually find the line sticking up from the ground right outside your house. From there, the line enters your home from the side of the house. It’s a good idea to locate your water main and the shutoff valve before you ever need to turn off the water. To protect the main water supply line from freezing, the line may come into your home in the basement or crawl space if you live in a cold zone.

Regardless of geographic location, most municipal building codes require that the main water lines are buried about three feet underground. The portion of the main line that runs under your property and into your home is usually your responsibility to maintain and repair. The city is responsible for maintaining anything from the end of your property line to the municipal water line.

After the line enters the inside of your home, it splits into two separate paths. One leads to the water heater, while the other carries cold water throughout your home. These paths are the cold and hot service lines. The main water service line has a meter that keeps track of your water usage—reflected in your monthly water bill.

Types of Water Supply Lines

In addition to main water service lines, residential plumbing systems rely on cold and hot water service lines. These two lines typically travel in pairs as they wind their way to each service outlet.

There are caveats!

Not all water fixtures use hot and cold water. While bathroom sinks need both supply lines, since toilets don’t use hot water, they only need a single cold water line. Dishwashers only need a hot water supply line. Some water-using appliances use an additional water supply line.

A washing machine, for example, uses a supply line, typically made from rubber or braided stainless steel. The supply line used for toilets is usually either plastic or stainless steel.

In most cases, manufacturers color-code water supply lines as follows:

• Red – hot water
• Blue – cold water
• White – either cold or hot water

Don’t let a white—or gray—water supply line throw you off. PEX pipes come in all four colors. It’s not uncommon to see them installed in white, gray, or a combination.

Where Are Water Supply Lines Located?

Knowing about the different types of water supply lines is not enough. As a homeowner, you’re on first response duty when you have a plumbing system problem. If you know where to find each supply line, you can often prevent further water damage. Knowing how to locate the supply lines help keep you a step ahead of leaks and mold development caused by hidden water damage. Plumbers install water supply lines in the following areas:

Kitchen

You can locate water supply lines in the kitchen by opening cabinets under the kitchen sink. There, you’ll find supply lines for the sink and the dishwasher.

You may also have a cold water supply line that connects to your refrigerator’s ice maker.

Bathroom

Like the kitchen sink, the sink in the bathroom has water supply lines underneath a cabinet. Plumbers locate the water supply lines for the toilets on the wall behind the toilet.

The other bathroom supply lines aren’t so easy to find. Water supply lines for showers and bathtubs run behind the walls.

Basement

If you go to the basement of a home and look up, you’ll likely see plumbing pipes. The pipes also run down walls connecting to appliances like the water heater and washing machine.

Of course, the plumbing won’t be visible if you have a finished basement since most homeowners cover the pipes with drywall. Plumbers usually locate the main water supply line underneath the concrete if you live in a home built on a slab.

What Are the Different Types of Water Supply Tubing?

From its beginnings—around 4,000-3,000 BC—materials used to construct plumbing systems have evolved from clay, straw, and lead to some of the best tubings for water supply lines on the market today. Before 1970, plumbers used galvanized steel supply lines. During the 1970s, copper displaced galvanized steel and became the gold standard for residential plumbing installations. By the 1980s, the plumbing industry saw more changes to the types of materials used for water supply lines. While copper remained the most common material, the industry introduced chlorinated polyvinyl chloride (CPVC) piping. In some areas of the US, plumbers used Polybutylene (PB) pipes. Plumbers today use both CPVC and its close relative, polyvinyl chloride (PVC). PVC makes a suitable option for piping water to the house but not for cold or hot water service lines.

CPVC versus PVC Tubing

Since it’s a common plumbing material, many people assume PVC piping works for all plumbing applications. That’s not entirely accurate. PVC piping is an excellent material for drainage, but it’s not suitable for carrying potable water. You may notice PVC used for the following:

• Sink and shower drains
• Spa and swimming pool lines
• Irrigation piping

PVC has multiple benefits. It’s durable, lightweight, and tolerates high water pressure. You’ll rarely see rust or corrosion in PVC tubing. So, why shouldn’t you use it for a water supply line?

The chemicals in this tubing are toxic when introduced into drinking water. Some countries have gone so far as to restrict its use.

PVC tubing has a peak temperature threshold of 140° Fahrenheit. Many water-using appliances work best at or below 140° Fahrenheit, including dishwashers, washing machines, and water heaters. The fact that PVC—due to its plastic property—cannot withstand hot water is another reason to choose a more suitable supply line material. Between the two, a better solution for water supply lines is CPVC. Known for resistance and superior performance, CPVC has a higher peak temperature threshold at just under 200° Fahrenheit. Many plumbers prefer CPVC tubing for hot water delivery.

What About PEX?

Cross-linked polyethylene (PEX) is a flexible plastic introduced in the US during the 1980s. While this material faced some challenges early on, today’s PEX makes an excellent solution for water supply lines. Sometimes referred to as a new-generation plumbing material, plumbers use PEX for new construction and remodeling projects. They use it for water supply lines, but many plumbers use PEX for radiant floor heat and residential sprinkler systems. PEX tubing has several advantages over some of the other tubing used for water supply lines, including the following:

• Corrosion-resistant
• Flexible
• Quiet
• Cost-effective

Corrosion-resistant tubing reduces the risk of leaks. PEX expands, which helps tubing resist freezing during cold snaps. Water flows quietly through PEX tubing—no noise caused by a water hammer. PEX piping is affordable, particularly when compared to the cost of copper tubing. When pricing the supplies for water lines, a plumber is always the best reference. Your plumber can also go into detail about each type of supply line material.

Copper Tubing for Supply Lines

Copper tubing is one of the oldest supply line materials on the market. It’s also more expensive than other materials used for water supply lines. Plumbers and homeowners like copper tubing for various reasons, including:

• Versatility
• Heat resistance
• Corrosion resistance
• Anti-microbial properties

Because it’s heat-resistant, copper works well for cold and hot water service lines. Plumbers also use copper for other plumbing applications beyond water supply lines.

Not only does copper resist corrosion, but it’s also safe for potable water delivery. Using copper tubing in water supply lines can inhibit the growth of bacteria in the tubing, which helps keep drinking water safe. One disadvantage of using copper tubing is that it costs twice as much as plastic tubing.

What Factors Should I Consider When Selecting the Water Supply Line Tubing?

With the range of materials available for water supply lines, it can seem confusing when you need to select the right one for your plumbing project. Price is always one determining factor, particularly when choosing between copper and CPVC or PEX plastic tubing. Copper costs more than the other two materials. Therefore, many people go with plastic due to rising prices. Durability is another factor to consider. We’ve already discussed corrosion and heat resistance. Don’t forget to evaluate each material on how easy it is to cut without causing damage. You’ll also want to understand how well the supply line you’re considering withstands water pressure.

Savvy homeowners choose the water supply line materials that give them the most for their money. Not all materials have the same lifespan.

Common Water Supply Line Problems

One of the essential elements of a house is smoothly working water lines. The health and comfort of every household member depend on an uninterrupted flow of fresh water.

Here are the most common issues that occur in residential water lines:

Noisy Pipes

Earlier, we mentioned the water hammer. Usually, water moves through pipes and supply lines without making much noise. However, if you have air in the pipes, a pipe clog, or excess pressure in your plumbing system, you may hear a sharp banging noise coming from the pipes.

One DIY solution to noise is to drain the water supply line.

Leaks

Leaks can happen anywhere in your water line. Corrosion in the line is one cause of leaks. A leak can result in low water pressure. While dealing with noise in the water lines isn’t usually urgent, discovering a leak means it’s time to call a plumber.

Low Water Pressure

Leaks, clogs, sediment buildup, and mineral deposits can cause low water pressure. It can also originate in your city’s water supply. Once you locate the cause of low water pressure, you may need to repair the water line. It’s also possible that you’ll need to replace part of the line if there’s damage. Troubleshooting low water pressure isn’t easy, and it’s always a good idea to have a plumber evaluate the issue.

How Do I Know If My Water Lines Need to Be Repaired or Replaced?

Whether you have a problem with the main water line to your home or your cold and hot water service lines, it’s not always easy to know whether you need a repair or replacement. Your plumbing system may give you one of the following clues:

• Low water pressure
• Noisy taps
• Frequent clogs
• Odor when running water
• Poor taste quality
• Discolored water
• Poor water heater performance
• Increased water bills

Another clue is that you have a water main line issue that is visible outside your home. Puddles or unusually green grass in the area above where your main water line sits may mean you have an underground leak. Any of these clues may indicate a break or an obstruction in one of your water supply lines.

How Does My Water Supply Line Impact My Water Quality

Water line corrosion can happen in homes of all ages, but if you live in an older home, it could be a significant problem. Corrosion can affect water quality by introducing contaminants into your drinking water. Although copper supply lines are corrosion-resistant, over time, they can corrode. This leads to an increase in copper levels in your water. When this happens, your water may smell and develop a metallic taste. If bacteria, mold, and algae develop in water supply lines, it can make people sick. It can also be fatal. Another issue caused by corrosion in water lines is staining. When water comes out of the tap, and it’s red or green, you may notice stains in sinks, showers, and drains. These stains are difficult to remove. Poor water quality can damage your plumbing system. It can also reduce the efficiency of your water heater and other water-using appliances. Your plumbing professional can test your water and make the appropriate repairs, including water line replacement.

Improving Efficiency and Pressure with Water Supply Lines

One of the biggest complaints of homeowners regarding water pressure is that it’s too low. Low water pressure is not only noticeable, but it can also disrupt everything related to water usage in your home. High water pressure is also troublesome and a significant cause of leaks, water supply line, and pipe damage. It also results in wasted water. Your plumber can help you improve your water pressure issues and problems related to poor efficiency in your plumbing system. One remedy for water pressure issues is to replace your water supply lines. As we’ve already discussed, water lines can develop corrosion or a buildup of mineral deposits, rust, and other debris over time. Clogged pipes often result in low water pressure. If you live in a home with aging plumbing and you’ve installed new plumbing fixtures, you may need to replace the old branch lines. The lines may not be clogged, but if they’re too narrow, you may experience water pressure issues.

If you and your plumber decide that replacing the water supply line is the answer, you will be undertaking a significant project. However, after installing new supply lines, you may never need to worry about replacing the pipes for the rest of the time you live in your home.

Under What Circumstances Should I Turn Off My Water Supply Line?

As the first line of defense, the homeowner can prevent water damage when there’s a plumbing problem. That’s why it’s vital to know how to locate the main shutoff valve and how to use it. While it’s not something most people do often, shutting off the water supply line to the entire house can save the day when there’s a burst pipe or broken water supply line.

Another situation when you’ll need to turn off the water supply line is when making repairs to a plumbing fixture or a water-using appliance. It only takes a minute to check all your water supply lines quickly.

Under the kitchen and bathroom sinks, you’ll find hot and cold service lines with handles to turn off the water supply. Likewise, all toilets in the house have a separate water supply line that you should turn off when dealing with clogs or making repairs. What about the water supply line to the water heater? Sometimes homeowners will turn off the water to the water heater when they’re away for an extended period. While it’s OK to do that for extended vacations, if you only plan to be gone for a weekend, you should not turn off the water supply to this appliance.

Another situation that rarely happens is a loss of pressure on the cold-water side. In that situation, you would turn off the water supply and the water heater.

When making repairs to washing machines and dishwashers, you’ll need to turn off the water supply to the appliance. Repairing ice makers or water dispensers on refrigerators also requires shutting off the water supply.

What Is the Cost of Fixing or Replacing a Water Supply Line?

Repairing or replacing water pipes and supply lines is usually not something homeowners plan for in advance. Often, a plumbing emergency makes the repair necessary. That makes it difficult to budget for these plumbing repairs. Your cost will depend on the severity of the repair. There’s a significant difference between repiping a house and replacing only a section of piping. For example, if you need to replace a main water line, it could cost between $1,500 and $12,000.

Four factors work together to determine cost. They include:

• Material
• Type
• Labor cost
• Line length

While some homeowners consider repairing or replacing plumbing elements—even water supply lines—themselves, working with water supply lines isn’t the best DIY project. You may save money but also spend much more than you planned if something goes wrong.

We Can Help With Any Plumbing Problem

Repairing or replacing a water supply line is not a small endeavor. Working with plumbing requires a unique set of tools and expertise, even if you’re a highly-skilled DIYer. The expert plumbing professionals at Atomic Plumbing and Drain Cleaning understand how critical your plumbing system is to your comfort, health, and peace of mind. Since 1968, we’ve taken care of the plumbing needs of our customers in Virginia Beach and the surrounding area.

Contact us today to schedule plumbing and drain service.