15.2 Water Wells, Pumps & Irrigation Systems
Key Takeaways
- FPC Table 614.1 sets the minimum private potable water system pump size by the number of bathrooms in the home: 7 gpm for 1 bathroom, 10 gpm for 1 to 1-1/2, 14 gpm for 2 to 2-1/2, 17 gpm for 3 to 4 and 21 gpm for 5 to 6 bathrooms.
- FPC Section 614.2 requires pressure tank drawdown of at least 1 gallon for every gallon per minute produced by the pump, excepting pump start applications, constant pressure devices and variable speed pumps.
- FPC Section 318.1 prohibits installing irrigation and sprinkler systems and risers for spray heads within 1 foot of the building sidewall.
- FBC-Plumbing Appendix F requires pipe cover of 18 inches for 1/2 to 2-1/2 inch pipe in vehicle traffic areas and 6 inches for 1/2 to 1-1/2 inch pipe elsewhere, with sleeves two pipe sizes larger extending at least 3 feet beyond paving.
- Appendix F requires an approved air gap or a reduced pressure principle assembly complying with ASSE 1013 where chemicals are injected into an irrigation system supplied from a municipal water supply.
Water Wells, Pumps & Irrigation Systems
The second sub-topic of Content Area F is water wells and irrigation systems. In Florida these two subjects arrive together constantly: a great many homes and nearly every commercial landscape draw irrigation water from a shallow well rather than from the potable main, and the plumbing contractor is the trade that sets the pump, the tank and the backflow protection.
1. Private Water Wells
Who Regulates What
- Well construction and the well contractor's license are regulated by the water management districts under delegation from FDEP, through FAC Chapters 62-524, 62-531 and 62-532. Drilling, casing, grouting, and well abandonment are water well contractor work.
- The plumbing side of the system — the pump, the pressure tank, the piping into the house, and the cross-connection protection — is FPC Section 614, Well Pumps and Tanks Used for Private Potable Water Systems.
- Onsite sewage setbacks to the well come from the onsite sewage rule covered in Section 14.1: 75 feet from a private potable or multi-family water well, 50 feet from a non-potable well, 100 or 200 feet from a public drinking water well depending on flow.
Terminology the Exam Uses
| Term | Meaning |
|---|---|
| Static water level | Depth to water in the well when the pump is off |
| Pumping (dynamic) water level | Depth to water while the pump runs at a given rate |
| Drawdown | The difference between static and pumping level; the drop the aquifer must sustain |
| Well yield | Sustainable flow the well can deliver, in gpm |
| Casing | The pipe lining the bore, sealing off shallow contaminated water |
| Annular grout seal | Cement or bentonite between casing and bore that blocks surface water from running down the outside of the casing |
| Screen | The perforated or slotted section admitting water in an unconsolidated aquifer |
| Pitless adapter | A below-frost, below-grade sanitary connection through the casing wall |
| Shallow well jet pump | Suction lift pump, limited to roughly 25 feet of lift at sea level |
| Deep well jet pump | Two-pipe jet assembly placed down the well to defeat the suction lift limit |
| Submersible pump | Motor and pump set below the water surface — the Florida standard for deeper wells |
The 25-foot suction limit is physics, not preference: atmospheric pressure supports a column of about 34 feet of water at sea level, and friction, vapor pressure and pump inefficiency reduce the practical lift to roughly 25 feet. Beyond that you place the pump down the well.
FPC Section 614 — Pumps
614.1 Pumps: well pumps used for potable water shall comply with 614.1.1 and 614.1.2.
Table 614.1 — Minimum Private Potable Water System Pump Size
| Bathrooms in Home | 1 | 1 to 1-1/2 | 2 to 2-1/2 | 3 to 4 | 5 to 6 |
|---|---|---|---|---|---|
| Minimum pump size (gpm) | 7 | 10 | 14 | 17 | 21 |
The table's notes add that the values are averages that do not include higher or lower extremes, and that installations over six bathrooms shall be approved by the code official.
614.1.1 Pump Installation: pumps shall be installed for operation without repriming or breaking suction, and shall be connected to the well head by a union, companion flange or compression coupling so the pump is accessible for maintenance, repair and removal. A pump hard-piped to the casing has to be cut out to be serviced.
614.1.2 Pump Sizing: minimum pump size shall be determined by Table 614.1.
FPC Section 614.2 — Pressure Tanks
Tanks shall rely on expansion of a flexible membrane within a restricting container, or be direct water-to-air interface tanks. Every pressure tank storing potable water under pressure shall be identified by seal, label or plate showing the manufacturer's name and model number, shall be constructed of steel, fiberglass or comparable materials, and shall meet this sizing rule:
Pressure tank drawdown shall be a minimum of 1 gallon for every gallon per minute produced by the pump. Exception: pump start applications, constant pressure devices and variable speed pumps.
Worked example. A three-bathroom home takes a 17 gpm pump from Table 614.1. Section 614.2 then requires a pressure tank with at least 17 gallons of drawdown — not 17 gallons of tank volume. Because drawdown on a typical 30/50 psi bladder tank is roughly 25 to 30 percent of nominal tank volume, a 17-gallon drawdown calls for a tank of roughly 60 to 70 gallons nominal. Undersizing here is the classic callback: the pump short-cycles, the motor overheats and the bladder fails inside a year. The exception exists because a variable speed or constant pressure pump modulates instead of cycling, so the stored volume is no longer the anti-cycling device.
2. Turf and Landscape Irrigation
Florida publishes an entire irrigation code as FBC-Plumbing Appendix F, Proposed Construction Building Codes for Turf and Landscape Irrigation Systems. Its stated purpose is uniform minimum standards for safe, cost-effective, reliable systems that promote the efficient use and protection of water and other natural resources. It applies to residential and commercial landscape areas, and expressly does not apply to golf courses, nurseries, greenhouses or agricultural production systems.
Permits and Submittals
- A permit is required to construct, enlarge, alter, modify, repair or move any irrigation system, or install or alter regulated equipment. No permit is required for general maintenance or repairs that do not change the structure or alter the system and whose value does not exceed $600 in labor and material based on invoice value — but exempt work still has to comply with the code.
- Single-family residence: design or shop drawings to reasonable scale showing the entire site and improvements, which may be prepared by a properly licensed qualified contractor.
- Commercial, industrial, municipal and multiple-family: professionally designed drawings showing date, scale, revisions, legend, specifications, water source, meter or point of connection, backflow prevention devices, pump station size and location, design operating pressure and flow rate per zone, precipitation rate per zone, and locations of pipe, controllers, valves, sprinklers, sleeves and gate valves.
The One-Foot Rule
FPC Section 318.1, Irrigation, is a Florida amendment and it is short: "Irrigation/sprinkler systems and risers for spray heads shall not be installed within 1 foot (305 mm) of the building sidewall." Keeping spray off the wall protects the termite treatment zone and the stucco, and this one-line section is exactly the sort of Florida-specific amendment the exam likes.
Materials (Appendix F Part IV)
- PVC pipe complying with ASTM D1785, ASTM D2241, AWWA C900 or AWWA C905. SDR-PR pipe shall have a minimum wall thickness as required by SDR-26. Solvent-weld fittings shall meet at minimum Schedule 40 per ASTM D2466; threaded PVC fittings Schedule 40 per ASTM D2464; gasketed fittings ASTM D3139 with ASTM F477 gaskets.
- Steel pipe shall be Schedule 40 or greater, hot-dipped galvanized or black to ASTM A53, with Schedule 40 malleable iron threaded fittings.
- Polyethylene flexible swing joints shall be thick-walled with a minimum pressure rating of 75 psi per ASTM D2239.
- Valves shall have a maximum working pressure rating not less than 125 psi, waivable for low mainline pressure systems at 30 psi or less.
- All pipe, sprinklers, valves and valve boxes used with effluent (reclaimed) water shall be designated for nonpotable use by label or by the industry standard color purple, and hose connections shall not be provided on nonpotable irrigation systems.
Installation (Appendix F Part V)
Depth of cover meets or exceeds SCS Code 430-DD:
| Pipe Size | Vehicle Traffic Areas | All Other Areas |
|---|---|---|
| 1/2 to 1-1/2 inch | 18 inches (1/2 to 2-1/2 in.) | 6 inches |
| 2 to 3 inch | 24 inches (3 to 5 in.) | 12 inches |
| 4 to 6 inch | 30 inches (6 in. and larger) | 18 inches |
| More than 6 inch | 30 inches | 24 inches |
Other installation rules that make good exam items:
- Thrust blocks must be used on all gasketed PVC systems, formed against a solid, hand-excavated trench wall undamaged by mechanical equipment, constructed of concrete filling the space between pipe and trench to the height of the pipe's outside diameter, and sized per ASAE S-376.1.
- Initial backfill shall be free from rocks or stones larger than 1 inch, and blocking or mounding shall not be used to bring pipe to final grade.
- Pipe sleeves under pavement shall be two pipe sizes larger than the carrier pipe (or twice the diameter of the wire bundle), extend at least 3 feet beyond the paved area, and have a wall thickness at least equal to Schedule 40 or PR 160, whichever is thicker.
- Valve boxes: top of the valve body shall have at least 6 inches of cover in nontraffic and noncultivated areas and 18 inches in traffic areas; boxes shall not rest on the pipe and shall sit flush with grade.
- Sprinkler separation: at least 4 inches between sprinklers and pavement, and at least 12 inches between sprinklers and buildings and other vertical structures. Intentional direct spray onto walkways, buildings, roadways and drives is prohibited.
- Pop-up height shall clear the turf: 6 inches for St. Augustine, Zoysia and Bahia; 4 inches for Bermuda, Centipede and Seashore Paspalum.
- Low-voltage wire: minimum #14 AWG single-strand control wire except on single-lot residential systems, buried at least 12 inches where not directly under the mainline, with white reserved for common wires, UL-approved direct-burial connectors, and all splices enclosed within a valve box.
- Rain switch: mounted on a stationary structure with a minimum 5-foot clearance from other outdoor equipment, clear of tree canopy and overhead obstructions, and above the height of sprinkler coverage. Soil moisture and evapotranspiration sensors are installed and monitored per manufacturer guidance under FS Section 373.62.
Backflow Protection — The Critical Item
Appendix F Part II requires backflow prevention assemblies at all cross connections with all water supplies, in accordance with county, municipal or other applicable codes, and adds the tiebreaker: "In the event of conflicting regulation provide the assembly type which gives the highest degree of protection."
For chemical injection the requirement hardens:
- Systems into which chemicals are injected shall conform to FS Sections 487.021 and 487.055 and to EPA Pesticide Regulation Notice 87-1.
- For municipal water supplies, chemical injection equipment must be separated from the water supply by an approved air gap separation or a reduced pressure principle assembly approved by the Foundation for Cross-Connection Control and complying with ASSE 1013, protecting against both back-siphonage and back-pressure.
- For other supplies, Florida law, EPA regulations or local codes apply, and in the absence of legal guidelines at least a pressure vacuum breaker should be used.
On the building side, the hose bibb used to feed a portable sprinkler is covered by FPC Section 608.16.4.2, which requires sillcocks, hose bibbs and wall hydrants to be protected by an atmospheric-type or pressure-type vacuum breaker or a permanently attached hose connection vacuum breaker, and FPC Section 608.16.4 sets the critical level of a pipe-applied vacuum breaker not less than 6 inches above the flood level rim of the fixture, receptor or device served.
A three-bathroom Florida home is served by a private well. What minimum pump size and pressure tank drawdown do FPC Table 614.1 and Section 614.2 require?
Under FBC-Plumbing Appendix F, what depth of cover is required for 1-inch irrigation pipe installed in a landscape area with no vehicle traffic, and for 2-inch pipe crossing a driveway?
An irrigation system fed from a municipal water main will have fertilizer injected into it. What backflow protection does FBC-Plumbing Appendix F require?
Where does FPC Section 318.1 prohibit installing irrigation sprinklers and spray head risers?