Modern plumbing, including proper sanitary drainage, is one of the reasons that diseases such as typhoid fever, cholera and dysentery have been eliminated. Modern plumbing has improved human health and longevity.

Hot water is defined as water of a temperature of 110° F (43° C) or hotter. Tempered water ranges from 85° F to 110° F (29° C to 43° C), and the device supplying the tempered water must limit the temperature to 110° F (43° C).

Ball valves are less restrictive to flow than other valves. The handle clearly indicates whether the valve is open or closed. Ball valves do not control water flow.

Globe valves tend to be restrictive, but can be used to control water flow.

In the connection of a water distribution system to water-heating appliances, there is the potential for the migration of heated water into the water distribution piping. In a typical water distribution system, the water will expand into the public water service. If the expansion of water is not accommodated in the system, dangerously high pressures can develop that can cause damage to piping, components and the water heater.

The minimum static pressure at the dwelling entrance for either public or private water service (as determined by the local water authority) should be 40 psi (276 kPa). The maximum static pressure should be 80 psi (552 kPa). When the pressure from the public water main or private well exceeds 80 psi, a pressure-reducing valve or regulator should be installed at the point where the water service pipe enters the dwelling. The pressure regulator should be installed immediately downstream of the main shut-off valve. To allow a continuous flow of water to the dwelling, the water pressure-reducing valve is designed to remain in an open position if the component fails.

PEX Plastic Tubing

PEX is polyethylene cross-linked plastic tubing. The cross-linked structure prevents the pipe from rupturing over a wide range of temperatures and pressures. PEX is resistant to solvents and cannot be joined by solvent cementing. PEX is flexible and can be bent. PEX can be hot-bent with a hot-air gun. The minimum hot-bending radius is 2½ times the outside diameter. PEX can be cold-bent, too (at room temperature) to a minimum radius of 6 times the outside diameter.

Condensate drains from air conditioner coils, condensing furnaces, and heat-recovery ventilators should not drain directly into a DWV pipe. An indirect drain using an air gap should be installed. In some locations, the direct connection of a condensate drain line into a stack is not permitted, even with a trap. The potential danger is that sewer gases may enter the house through the condensate drain line. It is not a cross-connection problem, but it is unsafe and unhealthy. www.nachi.org & www.apollohome.com

An air gap in a drainage system is the unobstructed vertical distance of free space between the outlet of the waste pipe and the flood-level rim of the receptacle into which the waste pipe is discharging. As an example in a commercial restaurant, the air gap would be between the drainpipe of a salad bar and the floor sink or tub drain.

There are deep wells (more than 25 feet deep) and shallow wells (25 feet or less). A typical well pump can pull up about 25 feet of water. If the well is deeper than 25 feet, the pump will have to be installed at the bottom of the well to push the water up. Pumps are better at pushing than pulling.