Potable Water Definitions

Front 1

Themovement, longitudinal spreading (via turbulence), and disappearance of asubstance being transported in a fluid (usually a dissolved substance).

Back 1

advection-dispersion-decay

Front 2

A partor piece of a larger system which advances and/or facilitates the purposes andfunction of the larger system. PW example: a gate valve.

Back 2

appurtenance

Front 3

Athrust block used in situations wherein the watermain (and the flow within it)changes direction in a vertical plane, as might happen when a watermain laidwith zero slope (passing through a flat area) must suddenly extend into an areathat is steeply sloping. The dead weight of the concrete of the block is usedresist the upward thrust. Sometimes called a vertical thrust block; they encompassthe elbow (say) and ‘hang' from it.

Back 3

ballast thrust block

Front 4

A typeof pressure gauge that is based on the uncoiling of an evacuated spiral oftubing, as the internal pressure increases within the coiled tube.

Back 4

Bourden gauge

Front 5

Avalve which involves the rotation of a circular plate about a vertical in-planeline through its axis, used in large diameter pipes.

Back 5

butterfly valve

Front 6

Therelationship between the head that a pump can generate (ordinate) and the flowthat it can produce (abscissa); has a negative slope and is unique to the pumpin question, and unique to the impellor installed in that pump.

Back 6

characteristic curve

Front 7

Asmall globe valve which is screwed directly into watermains, where the servicelateral connects to the watermain (at the upstream end of a lateral). It mustbe turned on before being buried.

Back 7

corporation stop

Front 8

Thephysical possibility of a flow reversal in a potable system, often backwardthrough a lateral. Caused either by back-siphoning or by a source of actualpressure in the building being serviced by the lateral. Often represents/causesa serious health hazard to consumers. Preventable through the installation andmaintenance of proper appurtenances, such as reduced-pressure-principlebackflow prevention valves.

Back 8

cross-connection

Front 9

Installationof vacuum breaker valves on an irrigation system.

Back 9

cross-connection control - example

Front 10

Avalve in a service lateral, located at the property line. It is at the bottomof a service ‘box’, within which is a rod which can turn the nut on top of thecurb-stop-and-drain. The top of the sendee box (a.k.a. valve box) associatedwith this little valve should be in an obvious location; it has a recessed5-sided nut in its centre (so that a special tool is needed in order to operateit). This is the valve in one’s service lateral that is shut off by the waterutility (i.e.HalifaxWater) if you do not pay your water bill.

Back 10

curb stop and drain

Front 11

Apiece of property that enables the water utility to legally access the part ofits system that is within the easement, such as for maintenance purposes.Easements are typically strips of land that are located adjacent to and betweenprivate properties, and the services in question are below grade.

Back 11

easement

Front 12

Acommon type of valve in which a circular steel plate is raised or lowered usinga threaded rod. Stops the flow and isolates problems. Not used on largediameter water mains. In some cases the leading edge of the circular steelplate is covered with a thick polymer, to make a more watertight seal.

Back 12

gate valve

Front 13

Ahigh-speed pressure perturbation caused by such things as rapid valve closure,sudden pump stoppage, or the collapse of an air gap. Characterized at a givenlocation by unusually high (or unusually low) pressures that last for a briefmoment in time, but which can damage the pipeline.

Back 13

hydraulic transient

Front 14

Ashort thick circular collar that is made of metal and which is fitted withtooth-like pipe grippers that are located at regular intervals around thecircumference of the collar. This type of restraint is placed overpush-together (“Tyton”) joints and is intended to prevent the separation ofsuch joints. The forces being resisted are caused by the system pressure (150psi being a typical assumption) and momentum effects (usually much smaller).They are used when the installation of concrete thrust restraint (poured'blocks’) is difficult, and/or when the soil conditions are poor.

Back 14

mechanical restraint

Front 15

Anenergy loss that is not caused by pipe friction. Examples would include thosethat occurring at reservoir exits and at elbow fittings. Unlike pipe friction,minor losses occur at specific points in the system. Like pipe friction, theyare quantified as being some fraction of the kinetic head.

Back 15

minor loss

Front 16

Astructure that enables a water utility to draw off water at differentsub-surface elevations, within a water body such as a lake. These intakes makeit possible to draw water from where it has less suspended sediment. Not usuallyused unless the serviced area is large; often tower-like in appearance.

Back 16

multi-port intake

Front 17

Adevice that uses the stagnation principle to measure velocity, such as the velocityof the flow that is emerging from a fire hydrant. Converts kinetic head topressure head.

Back 17

Pitot tube

Front 18

Avalve that is used to both sustain and limit the pressure in a given downstreamzone of hydraulic head, in spite of fluctuations in demand that occurdownstream of the PRV chamber. PRV's make use of the upstream-downstreampressure difference to internally self-adjust. They are set such that thepressure that remains on the downstream side (and thus the hydraulic head onthe downstream side) remains constant.

Back 18

pressure reducing valve

Front 19

Avalve closure which occurs more quickly than the round-trip time to a reservoir(or other pressure relaxation point) in the potable system.

Back 19

rapid closure

Front 20

A valve closure which occurs less quickly than the round-trip time to a reservoir or other pressure relaxation point in the system.

Back 20

slow closure

Front 21

A trapezoidal block of concrete that is used to resistthe thrust exerted by watermains at locations where there is a change inplanimetric direction, such as at elbows. This thrust force is caused by thepressure of the water at the location of interest, and to a much lesser extentby the momentum change associated with the directional change of the flow.Thrust blocks

Back 21

thrust block

Front 22

Anengineering euphemism for the mineral deposit (internal scaling) that builds upon the inside of water mains (especially cast iron watermain), decreasingdiameter and dramatically increasing frictional effects.

Back 22

tuberculation

Front 23

Anengineering euphemism for hydraulic transients within potable waterdistribution systems. See hydraulic transient.

Back 23

water hammer

Front 24

soft or amorphous ice formed by the accumulation of ice crystals in water that is too turbulent to freeze solid.

Back 24

Frazil Ice

Front 25

Back 25

Tower intake

Front 26

Back 26

submerged intake

Front 27

Back 27

shore intake

Front 28

Back 28

PRV

Front 29

that hour of the day that requires the highest flow

Back 29

MHR

Front 30

day of the year that requires the highest flow rate.

Back 30

MDR

Front 31

calculations the examine whether a single path results in a flow that is larger than the fire flow at a given (very distance ) location especially on that is far away from a PRV.

Back 31

natural flow calculations