2.5 Identifying Water Supplies & Source Capacity

2.5 Identifying Water Supplies & Source Capacity

Quick Answer: A site may be served by more than one water source. Before touching a system, identify every supply: potable municipal service, private well, surface water (pond, lake, stream, canal), reclaimed or recycled water, and harvested rainwater or graywater. Each source dictates a different backflow assembly, filtration package, and capacity limit. Any auxiliary supply that can reach the potable system is a high-hazard cross-connection requiring an RP assembly.

The exam phrases this topic simply — Identify All Water Supplies — but it is the topic that most often turns a routine service call into a public-health incident. A homeowner who ties a pond pump into an existing municipal-fed mainline has created an unprotected cross-connection, and the technician who works on that system without recognizing it inherits the liability.

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1. The Five Source Types

Potable Municipal Service

The most common landscape supply. Water arrives already pressurized and disinfected through a service line and a revenue meter.

• Pressure: typically 45-80 psi static; verify at the point of connection, never assume.
• Capacity limit: set by the service line size and the meter, not by the main.
• Cost: metered; often includes sewer charges unless a separate irrigation (deduct) meter is installed.
• Backflow: required by code on every irrigation connection.

Private Well

• Equipment: submersible or jet pump, pressure tank, pressure switch, and often a sand separator.
• Capacity limit: the sustainable yield of the well in GPM, not the pump's rating. Over-pumping draws the water level below the pump intake, breaking suction and burning the motor.
• Quality: commonly carries sand, iron, manganese, hardness, and sulfides. Iron and manganese stain hardscape and plug drip emitters; hardness scales nozzles.
• Regulatory: many jurisdictions require a well permit, annual testing, and a physical separation from any municipal connection.

Surface Water (Pond, Lake, Stream, Canal)

• Equipment: centrifugal or turbine pump with a foot valve and intake screen; the intake must sit above the bottom sediment and below the low-water line.
• Quality: heavy organic load — algae, duckweed, plankton, leaf litter — plus seasonal turbidity. Disc or media (sand) filtration is generally required; a screen filter alone blinds off quickly against algae.
• Regulatory: withdrawal usually requires a water right, permit, or allocation.

Reclaimed / Recycled Water

Treated municipal effluent distributed for irrigation. Rapidly expanding in the arid West and in Florida.

• Identification (memorize this): Pantone 522C purple pipe, valve boxes, valve box lids, and sprinkler bodies; components stamped or taped "CAUTION: NONPOTABLE WATER - DO NOT DRINK"; signage at the site perimeter and at each controller.
• Hardware rules: hose bibbs are removed or made non-removable/locking; quick-coupler valves use a different key type from potable quick couplers so a potable key cannot open a reclaimed valve.
• Hazard class: high hazard. Where a reclaimed system shares a site with a potable system, an RP assembly protects the potable side, and physical separation distances between reclaimed and potable piping are specified by local code.
• Quality: typically elevated salts, sodium, and nutrients; some plants show foliar burn from overhead application.

Harvested Rainwater, Stormwater & Graywater

• Rainwater: cistern-fed, gravity or pump pressurized; low mineral content but carries roof debris; requires a first-flush diverter and screening.
• Graywater: laundry, shower, and lavatory discharge. Highly regulated; typically restricted to subsurface distribution, and never permitted through overhead spray heads.
• Backflow: any of these connected to a system that also has a potable supply is an auxiliary supply = high hazard = RP.

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2. Capacity: How Much Water the Source Can Actually Deliver

Identifying the source is only half the job. The technician then has to determine what it can supply.

Municipal Meter Capacity

Displacement meters have a maximum safe operating flow. Continuously exceeding it accelerates wear, drives enormous pressure loss, and in many jurisdictions violates the utility's terms of service. The standard irrigation design practice is to size zones so peak flow stays at or below roughly 75% of the meter's maximum safe flow.

Always confirm the rating stamped on the specific meter and any utility limit; the values above are the common AWWA displacement-meter classes.

The Three-Part Field Capacity Check

1. Static pressure at the point of connection with all flow stopped (see Section 5.1).
2. Available flow, measured — not assumed (see Section 2.6 for the meter and bucket methods).
3. Service line size and material, because a 3/4 in. service line throttles the site regardless of meter size or main pressure.

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3. Multiple Supplies on One Site

When more than one source serves a property, the technician must document how they are separated:

• Is the auxiliary supply physically disconnected from the potable system, or connected through an approved assembly?
• Which zones are fed by which source, and is that recorded on the as-built?
• Are reclaimed components correctly colored, labeled, and keyed?
• Does the controller reflect the split — for example, a separate program for the well-fed zones whose flow limit differs from the metered zones?

Exam trap: "The pond pump only runs when the city valve is closed" is not an acceptable separation. Reliance on an operator or a valve position is never accepted as cross-connection control; only an approved assembly or a physical air gap is.