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Plumbing Basics

The topic of indoor plumbing is one that homeowners rarely concern themselves with—until they discover a leak, run out of hot water, or begin to remodel the house. While the temptation may be to call a plumbing contractor to handle things, a little patience and a willingness to experiment may make plumbing repairs more straightforward than you think.


Rough plumbing work is done in the framing stage of building a home. Here, a waste pipe is being installed.

System Basics
Water pressure is fuel for the plumbing system. Distributing, manipulating, and preserving water pressure is the plumber’s stock in trade. All plumbing fixtures, from simple laundry hoses to toilets to the nozzles on an expensive hot tub, are designed to operate within a fixed range of pressure, and it is the plumber’s job to ensure that each receives that pressure—no more, no less. The plumber and the plumbing designer rely on the internal diameter of the water delivery pipes to control water pressure. The smaller the pipe diameter, the higher the pressure and the greater the velocity of the water moving through it.

Plumbers rely on gravity to drive the drainage and waste removal portion of the plumbing system. The plumbing system must be properly vented to release all air pressure, or it will lose its flow. For that reason, the drainage and waste system is referred to as the “DWV” (drainage, waste, and vent) system.

Codes
Plumbing is both an art and a science. Most of what plumbers do when designing or repairing a system is dictated by local, state and federal codes. Codes specify the internal diameter of pipe that must be used for a particular plumbing section or function. In the water supply system, for example, pipe of increasingly smaller diameter is called for as the supply pipes branch out from the water main that enters the house. Water in the main is under tremendous pressure — far more than can be safely handled by the individual sinks, toilets and appliances in the home. The successive drop in pressure as the water moves from main, to primary supply lines to secondary supply lines ensures that each appliance receives an appropriate amount of pressure.

Codes also prescribe where shutoff valves should be placed, what pipe materials can be used for given functions, what kinds of fittings are needed to safely join pipes or create branches, and the amount of slope or downward drop that drain pipes need to function properly.

Plumbing Renovations

Old Homes, Old Pipes

When you are planning renovations to an older home, don’t be surprised if your plumbing contractor wants to do a thorough investigation before taking the job. Plumbers must be familiar with the properties of outdated plumbing components, such as iron or brass pipes, which they might encounter on a renovation job. At the same time they must know how to take advantage of the latest developments in plumbing technology, such as flexible plastic pipe.

Homeowners need to understand that the limitations of their system will likely impact their plumbing projects. You might plan to use an existing drain line to catch the flow from a new sink or toilet only to find that it doesn’t have enough capacity to handle the additional volume. Or, after purchasing a laundry tub for the basement you might discover that it can’t be connected because the main sewage or septic outlet is located above the basement floor. While you or your plumbing contractor may find solutions to such problems, its important to anticipate how plumbing can complicate your renovation plans and budget.

System Design
Laying out an efficient, well-designed system requires craftsmanship and experience. On the water supply side, the plumber must decrease water pressure as it enters the home from the water main, and preserve enough pressure throughout various parts of the system to provide adequate flow, even when several appliances are turned on at the same time. This manipulation of pressure is achieved entirely by varying the internal diameters of the pipes.

On the DWV side of things, calculating for downward slope, the correct internal diameter of a waste pipe, or adequate venting will determine how well your system sends waste water to the sewer or septic. What’s more, plumbing design requires an understanding of how to safely integrate a complex maze of pipes with the wires and ducts that travel through your walls.

Credit: Renovate Your World