Understanding the Basic Water Supply System for Plumbing

The labyrinth of pipes, fittings, valves, and fixtures that constitutes the plumbing system in your house can be a complex puzzle. However, like most devices and systems designed by human beings, it is only bewildering to those who are unfamiliar with it. Plumbing is just a series of rather simple and logical connections of pipe, fittings, and fixtures. You may find that making repairs or even adding on to the system is quite possible for you to do all by yourself.

Supply Lines and Branches

It all starts with your main supply line. If you get your water from a public water works, it will probably come from the water main under the street out front, through your water meter and your main shutoff valve. In areas where the ground freezes deeply in the winter, the meter will be in the basement or crawl space. In warmer areas, it will be in a little concrete wall near the curb. If you have a private water supply system, the main supply line will start at your storage tank or pump.

In any case, the supply line that enters your house should be at least ¾-inch pipe. One-inch pipe is even better if you are planning any additions or replacements. Obviously, the larger the pipe, the more water it can supply. But even more important, a larger pipe will cause less friction. When the water pressure is low, like during TV commercials when everyone uses their bathrooms at the same time, both the volume and friction factors are important to maintain a steady, even flow of water.

After the main line enters your house, it usually runs near the water heater. There it splits in two. The hot-water pipe goes through the water heater and then runs parallel to the cold-water pipe to the laundry, kitchen, and bathrooms throughout the house. At one or more convenient places in the basement or crawl space, the cold-water pipe branches to provide water to the outside faucets around the house and in the garden.

If the water entering the house must be treated in some way, the treatment units will be attached near where the water enters the house. Chemical injectors or filters will be on the main line in the basement or crawl space. Because softened water usually doesn't taste as good as hard water and because the added sodium is not considered healthy, water softeners are often placed on the branch line that goes to the water heater. This way only the hot water, used for washing and bathing, is softened. In some cases, although it makes the piping a little more intricate, un-softened water is piped to the kitchen sink and maybe a wet bar or faucet used primarily for drinking, while softened hot and cold water is piped to the laundry and bathrooms.

To make the plumbing system more economical to install and to keep pipeline friction to a minimum, architects and house designers try to locate bathrooms, kitchens, and laundries as close together as possible on the same floors and, when they are on different floors, directly above and below one another.

After the main supply line enters your house, it divides into ¾-inch hot and cold water pipes. The branches that feed individual fixtures may be of ½-inch pipe. These water systems may be made of galvanized iron, copper, or plastic, depending on local codes and practices and the age of the house. Building codes are very specific as to what kinds of pipe and fittings are required or allowed. Before you make any changes or additions, especially if you plan on changing from the kind of pipe you already have in your house, be sure to check with your building inspector.