Plumbing can seem daunting at first, but it can actually be broken down into a few basic components. Here's a guide for new home builders installing a plumbing system.
Setting the sewer accommodation stubs—that is, where the home's sewer line connects to the municipal sewerage system—marks the beginning of the plumbing system installation. This happens before the concrete foundation is poured.
The Rough-In Phase
What's called the rough-in plumbing phase—where the basic lines are laid without making the final connections—happens when the framing is complete, but before hanging the drywall. The main drains are all installed and connected to what's called the stack.
The stack is the vertical drain pipe that other drain pipes feed into. Waste or water flows downward, and a vent at the top allows air into the system, which enables the water to flow freely.
Rough-in drain fittings for sinks and bathtubs are also installed at this stage, as are the water supply pipes and toilet flanges.
Setting Large Plumbing Fixtures
Plumbing fixtures like showers and bathtubs are often too large to set once doorways and walls are framed. Any fixtures larger than sinks generally get set before the walls are framed.
Connecting the Fixtures
Sinks and toilets are set to last, after finishing the walls and flooring. From there, all the fixtures can be connected to the supply and drainage systems.
Water Supply System
The pressurized water supply enters the house through one main line. This must be set below the frost line—the depth to which groundwater will freeze—to keep the line from freezing and damaging your pipes.
Once the main line has entered the house, it's split into two lines. One supplies cold water while the other connects to the hot water system. From there, each appliance or fixture is supplied hot and cold water.
The drainage system consists of the main vent-and-soil stack (already mentioned) and the waste drains that connect to it. The stack directs waste to the main sewer drain, which exits the house below the frost line. From there it can tie into the municipal sewer system or run to a personal septic tank.
If you've ever tried to tip a bottle of liquid out by holding it vertically, you'll know why vent pipes are essential.
A constant source of air prevents water locks from forming in drainpipes, which can cause clogs. Most fixtures and appliances can share a common vent so long as they're connected within 10 feet of each other. If not, a separate vent pipe must be installed.
All vent pipes generally connect to the stack, allowing ventilation through the main stack vent. Sometimes separate vents must exit the home separately if the house's layout doesn't allow for easy connection.
Traps are generally the most recognizable part of the plumbing system. They're the U-shaped pipes that connect to the bottom of showers, sinks, or bathtub drains. Their role is to retain a small amount of water to prevent sewer gasses from backing up into the house.