Building Water System and Design Lecture Notes

This set of vocabulary flashcards covers fundamental units, fluid properties, pressure calculations, plumbing fittings, and water demand concepts based on the building water system design lecture.

Water (Pure State)

A molecule composed of one oxygen atom and two hydrogen atoms that is tasteless and odorless in its pure state.

Standard Atmospheric Pressure

The typical barometric pressure of air at sea level and $70^{\circ}F$ ($21^{\circ}C$), equal to $14.7\,psi$ ($101.325\,kPa$) for boiling point reference or exactly $14.696\,psia$ ($101\,325\,Pa$).

Specific weight (Density)

Weight per unit volume, commonly used as $62.42\,lb/ft^3$ ($1.00\,kg/L$) for liquid water in engineering computations.

Specific Gravity (s.g.)

The ratio of the specific weight of a fluid or solid to the specific weight of water at $39^{\circ}F$ ($4^{\circ}C$), the temperature at which water is most dense.

Volume (V)

The amount of space occupied by a substance, commonly expressed in gallons (g or gal) in plumbing design, where $1\,ft^3$ contains $7.48\,gallons$, and a gallon is approximately $3.8\,L$.

Volumetric Flow Rate (Q)

The volume of a substance that passes a point in a system per unit of time, determined by the equation $Q = V/time$.

Velocity (v)

The rate of linear motion of a substance in one direction, expressed as an average velocity in plumbing because molecules at the center of a pipe travel faster than those near the inner wall.

Pressure (P)

The force per unit area exerted by liquid or gas on a surface, such as the sidewall of a pipe, expressed in pounds per square inch ($lb/in^2$) or Pascals ($N/m^2$).

psi

The universally accepted acronym in the plumbing industry for pounds per square inch of gauge pressure.

psia

The acronym used to represent absolute pressure in pounds per square inch.

Gauge pressure (Pg)

The pressure of a fluid excluding the pressure exerted by the atmosphere.

Absolute pressure (Pa)

The total pressure of a fluid including the pressure exerted by the atmosphere, calculated as $P_g + P_s = P_a$.

Hydrostatic Force

A force exerted by the weight of the fluid against the walls of a vessel containing the fluid.

Residual Water Pressure

The water pressure available at the outlet just before the plumbing fixture.

Static Head

The pressure difference resulting from elevation change, calculated in customary units as $\Delta P_{static} = -0.433Z$ in $psi$, where $Z$ is vertical height in feet.

Friction Head (ΔPfriction)

Pressure losses resulting from friction, which relate to flow rate, fluid velocity, pipe diameter, material roughness, length, and the number of fittings and valves.

Elbow

A fitting installed between two lengths of pipe to allow a change in direction, usually $90^{\circ}$ or $45^{\circ}$.

Tee

The most common fitting used to combine or divide fluid flow; it can connect pipes of different diameters or change direction.

Compression Stop

A valve that uses a brass compression sleeve and a coupling nut to create a watertight seal against a copper pipe.

Gate Valve

A valve generally used to completely shut off fluid flow or provide full flow in the open position; it is not used for regulating flow.

Globe Valve

A valve with a rounded outside shape suitable for regulating flow or pressures as well as complete shutoff.

Water Meter

A device that measures the cumulative volume of water passing through a pipe, operating similarly to a car odometer.

Water Supply Fixture Unit (WSFU)

An arbitrarily chosen measure used to calculate the design load on a system by expressing different types of plumbing fixtures in common terms based on their flow rates.

Maximum Demand

The total water discharge of fixtures in a system where one fixture unit is valued at $8\,gallons$ per minute interval.

Probable Demand (Peak Load)

The estimated simultaneous use of fixtures; the probability of simultaneous use decreases as the total number of installed fixtures increases.