Chapter NR 811

NR 811.61 NR 811.61 General. The department may approve the use of hydro-pneumatic, or pressure, tanks, as provided in s. NR 811.62 (2). All of the following requirements shall be met:

NR 811.61(1) (1) The tanks shall be completely housed, or earth-mounded with one end projecting into an operating house, to prevent freezing. A tank may be installed below grade if one end is exposed in a basement, vault or manhole. If the tank is installed below grade, all electrical controls and air release valves and any other appurtenances which may permit contamination of the water supply shall be extended to at least 24 inches above grade. Air release piping extended above grade shall be terminated in a down-turned U-bend screened with a 24-mesh corrosion resistant screen. The basement, vault or manhole shall be constructed to prevent surface water from entering including sealing any annular spaces where pipes and appurtenances pass through a wall, floor or ceiling. The basement, vault or manhole shall be equipped with heating, ventilation and dehumidification equipment if necessary to prevent excessive corrosion of the pressure tank and associated piping or to prevent water from freezing. Access manholes shall terminate a minimum of 24 inches above grade with an overlapping, locking cover. Vent pipes shall be metal and terminate a minimum of 24 inches above grade in a downward facing U-bend screened with a 24-mesh corrosion resistant screen. Doors shall open outward and be provided with a lock.

NR 811.61(2) (2) Each tank shall be provided with bypass piping and the necessary shut-off valves to permit operation of the system while the tank is being repaired or painted. For galvanized or bladder type pressure tanks, the individual connecting pipe to each tank shall be provided with a shut-off valve, pipe union and drain fitting. Threaded drain fittings shall be provided with a vacuum breaker.

NR 811.61(3) (3) Each tank not equipped with a bladder or diaphragm to separate the air and water and with a gross volume of 500 gallons or more shall have a drain fitting with shut-off valve and control equipment consisting of a pressure gauge, a pressure relief valve, a water sight glass, an automatic air blow-off, and pressure or probe operated start-stop controls for the pumps.

NR 811.61(4) (4) Each tank not equipped with a bladder or diaphragm to separate the air and water and with a gross volume of 500 gallons or more or that will be painted inside shall be provided with an access manhole. If the tank interior is to be painted it shall be painted with NSF/ANSI approved paints in accordance with s. NR 810.09 (5).

NR 811.61(5) (5) Each tank not equipped with a bladder or diaphragm to separate the air and water and with a gross volume of 500 gallons or more shall be provided with an automatically controlled air compressor to add air to the tank. All compressors used to routinely add air to tanks shall be oil-less. Larger capacity compressors that are not oil-less may be used temporarily to fill a tank upon startup, repair or service but shall be fitted with one or more filters and any other appurtenances necessary to remove particulates and oil from the air prior to injection.

NR 811.61(6) (6) Each tank equipped with a diaphragm or bladder shall be equipped with an air inlet for adding air manually, a pressure relief valve for each tank or bank of tanks sized to handle the maximum flow rate, and pressure-operated start up and shut down controls for the well pump.

NR 811.61(7) (7) The gross volume, in gallons, of any tank or combination of tanks, shall be at least 10 times the maximum pump capacity, rated in gallons per minute, unless the proposed pump motor or motors will be controlled by a variable output control device in a manner intended to reduce the volume of required pressure tank storage in accordance with s. NR 811.34 (6).

NR 811.61 Note Note: The department recommends that the storage volume provides a minimum pump run time of at least 2 minutes.

NR 811.61(8) (8) Each tank shall be identified by stamping or labeling showing the manufacturer’s name, a serial number, the tank volume, the allowable working pressure, and the year fabricated.

NR 811.61(9) (9) Each tank not equipped with a bladder or diaphragm to separate the air and water and with a gross volume of 500 gallons or more shall be constructed of steel and have a 0.25 inch minimum side wall and head wall thickness.

NR 811.61 History History: CR 09-073: cr. Register November 2010 No. 659, eff. 12-1-10; CR 22-074: am. (7) Register January 2024 No. 817, eff. 2-1-24.

subch. IX of ch. NR 811 Subchapter IX — Storage Facilities

NR 811.62 NR 811.62 Volume and pressure.

NR 811.62(1) (1) Volume requirements. A sufficient quantity of water, as determined from engineering studies, shall be maintained in elevated storage when only one pumping unit to the distribution system is available to serve the water system. This shall be at least an average-day supply under normal operating conditions. When more than one distribution pump is available, the storage shall be in accordance with standard engineering practice. Standard engineering practice is based upon an engineering review of existing and future water supply needs including: type of service and population served; average day, maximum day, peak hour and fire flow demands and durations; water source quality, availability and treatment, pump capacities, auxiliary power, storage capacity, water distribution and costs.

NR 811.62(2) (2) Pressure requirements. Storage facilities shall be designed to meet all the following requirements:

NR 811.62(2)(a) (a) Minimum and maximum pressures. The storage facilities shall be designed to meet the minimum and maximum pressure requirements specified in s. NR 811.66 (1).

NR 811.62(2)(b) (b) Fire flows and residual pressures. When fire protection is to be provided, the storage facilities shall be designed in conjunction with distribution system design to provide the minimum fire flows and residual pressures specified in s. NR 811.70 (6).

NR 811.62(2)(c) (c) Alternative means for maintaining pressure. A hydro-pneumatic tank, booster pumping facilities, or other reliable means shall be provided to maintain system pressure when a gravity storage reservoir or tank is not available.

NR 811.62(3) (3) Elevated storage requirement waived. The department may waive the requirement for elevated storage if the system is designed to serve less than 50 homes, if it is not economically feasible to provide elevated storage, if elevated storage facilities are proposed for a later development phase, or if service is proposed for domestic use only.

NR 811.62 History History: CR 09-073: cr. Register November 2010 No. 659, eff. 12-1-10.

NR 811.63 NR 811.63 Location. Storage facilities shall be located in accordance with all the following requirements:

NR 811.63(1) (1) Floodway and floodplain.

NR 811.63(1)(a) (a) Floodway. Storage facilities may not be located within a floodway, as defined in s. NR 116.03 (22).

NR 811.63(1)(b) (b) Floodplain. If it is necessary to locate a reservoir in a floodplain, as defined in s. NR 116.03 (16), outside of the floodway, the lowest elevation of the bottom floor, including sumps, shall be a minimum of 2 feet above the regional flood elevation as determined in s. NR 116.07 (4). All projects shall conform to the requirements of that chapter.

NR 811.63 Note Note: Refer to ch. NR 116 for floodplain and floodway requirements.

NR 811.63(2) (2) Grading. The area surrounding structures shall be graded in a manner that will prevent surface water from standing within 50 feet of the structure.

NR 811.63(3) (3) Year-round access. Storage facilities shall be located in an area accessible during the entire year. If necessary, road improvements shall be installed to provide year-round dry land access. Storage facilities and access roads shall be located on property owned by the water supply owner or for which the owner has obtained easements.

NR 811.63(4) (4) Floor elevations. The department recommends that the lowest elevations of floors and sump floors of ground level reservoirs and standpipes should be placed at or above the normal ground surface. If the department allows the floor or sump to be below the normal ground surface, it shall be placed a minimum of 2 feet above the groundwater table. Borings shall be made to determine groundwater elevations if that information is not available.

NR 811.63(5) (5) Contamination sources.

NR 811.63(5)(a) (a) Sewers, drains, fuel storage tanks, standing water, and similar sources of contamination shall be kept a minimum of 50 feet from the ground storage reservoir.

NR 811.63(5)(b) (b) The department may approve gravity or force main sewers within 50 feet of a ground storage reservoir if the sewer or force main is constructed of water main class pipe meeting the requirements under s. NR 811.69 and is pressure tested in place to meet the requirements under s. NR 811.12 (5) (d) 2.

NR 811.63(6) (6) Roof surface above grade.

NR 811.63(6)(a) (a) The top roof surface of a ground level reservoir may not be less than 2 feet above normal ground surface.

NR 811.63(6)(b) (b) The department shall require a higher exposed elevation if high groundwater, poor surface drainage, or tight soils are encountered that will deter subsurface drainage or if necessary to provide positive pressures for pump intake or discharge lines in accordance with s. NR 811.37.

NR 811.63 Note Note: It is recommended that no more than one-half of the reservoir depth be constructed below grade.

NR 811.63(6)(c) (c) The department may except clearwells constructed under filters from the 2 foot requirement when the total design gives the same protection.

NR 811.63 History History: CR 09-073: cr. Register November 2010 No. 659, eff. 12-1-10; CR 22-074: am. (5) Register January 2024 No. 817, eff. 2-1-24.

NR 811.64 NR 811.64 Construction details.

NR 811.64(1) (1) Materials. Materials used in the construction of storage facilities shall meet all the following requirements:

NR 811.64(1)(a) (a) General requirements. The materials and designs used for finished water storage structures shall provide stability and durability as well as protect the quality of the stored water. Unless the design engineer can justify the use of other materials, the department shall approve only steel, fiberglass, or concrete for use in a water storage facility. Porous materials, including wood and concrete block, may not be used.

NR 811.64(1)(b) (b) AWWA standards. Structures shall be constructed in accordance with the AWWA standards D100, D102, D103, D104, D110, D115, D120, and D130 concerning steel; concrete or fiberglass tanks, standpipes, reservoirs, and elevated tanks in effect at the time of construction wherever they are applicable.

NR 811.64(2) (2) Protection. Storage facilities shall be constructed and maintained to protect the water supply in accordance with the following requirements:

NR 811.64(2)(a) (a) General requirements. All water storage structures shall have watertight roofs or covers which exclude surface water, rain, snow, birds, animals, insects and dust.

NR 811.64(2)(b) (b) Installation of ancillary equipment. The installation of ancillary equipment, such as antennas, shall be done in a manner that ensures no damage to the tank, coatings, or water quality. Any damage that occurs to the tank during installation shall be corrected.

NR 811.64(2)(c) (c) Adjacent compartments. Finished water may not be stored or conveyed in a compartment adjacent to nonpotable water when the 2 compartments are only separated by a single wall. The department may waive this requirement for backwash water holding compartments meeting potable water reservoir construction on a case-by-case basis.

NR 811.64(2)(d) (d) Security. Locks on access manholes, fences and ladder cage bottoms and any other necessary measures shall be provided to prevent trespassing, vandalism and sabotage.

NR 811.64 Note Note: The department recommends that intrusion alarms and/or motion sensors be installed as applicable and where feasible for elevated tank pedestal access doors and reservoir access hatches. The department recommends that high strength, cut resistant locks or lock covers be installed to prevent direct cutting of a lock.

NR 811.64(3) (3) Drains. Drains for storage structures shall meet all the following requirements:

NR 811.64(3)(a) (a) General drain discharge requirements.

NR 811.64(3)(a)1. 1. Piping used to drain water from a water storage structure shall discharge to the ground surface. The drain piping shall be brought down to within 12 to 24 inches of the ground surface and discharged with a free air break over a drainage inlet structure, splash pad or riprap.

NR 811.64(3)(a)2. 2. Reservoir drains may not be directly connected to a storm sewer. A WPDES permit is required for any discharge with a free air break over a storm sewer manhole or through a valved connection to the overflow piping.

NR 811.64(3)(a)3. 3. Reservoir drains may not be directly connected to a sanitary sewer. Water from drains may not be discharged to a sanitary sewer except on a temporary basis when the drain water contains sediment or chemicals used for cleaning, such as during temporary cleaning of water storage facilities.

NR 811.64(3)(b) (b) Impacts to the environment prohibited. Negative impacts to the environment from the discharge of drainage water shall be prevented.

NR 811.64(4) (4) Overflow. Each reservoir shall be provided with overflow piping meeting all the following requirements:

NR 811.64(4)(a) (a) General overflow discharge requirements.

NR 811.64(4)(a)1. 1. ‘Discharge.’ The overflow pipe of a water storage structure shall terminate downward facing from horizontal, 45-degrees at a minimum of 12 to 24 inches above the final graded ground surface with a free air break over a drainage inlet structure, splash pad, or riprap. A WPDES permit is required for any discharge with a 12 to 24 inch free air break over a storm sewer manhole. Overflows may not discharge to a sanitary sewer.

NR 811.64(4)(a)2. 2. ‘Pipe diameter.’ The overflow pipe shall be of sufficient diameter to permit wasting water in excess of the maximum filling rate.

NR 811.64(4)(a)3. 3. ‘Pipe material.’ The overflow pipe shall be constructed of ductile iron, steel, or stainless steel.

NR 811.64(4)(a)4. 4. ‘Visibility.’ All overflow pipes shall be located so that any discharge is visible.

NR 811.64(4)(a)5. 5. ‘Flapper.’ If a metal flapper valve is used, a screen shall be provided in accordance with pars. (c) and (d).

NR 811.64(4)(a)6. 6. ‘Rubber duckbill valve.’ If a rubber duckbill valve is used, a screen is not required. Provisions shall be included to prevent the duckbill from freezing shut.

NR 811.64(4)(a)7. 7. ‘Overflow location.’ An internal overflow pipe on an elevated storage tank shall be located in the access tube and discharge in accordance with par. (a). Internal overflows are prohibited on standpipes, ground storage reservoirs, and ground level storage tanks.

NR 811.64(4)(b) (b) Impacts to the environment prohibited. Negative impacts to the environment from the discharge of overflow water shall be prohibited.

NR 811.64(4)(c) (c) Elevated tanks and standpipes. The overflow pipe shall be provided with a 4-mesh corrosion resistant screen installed within the pipe at a location least susceptible to damage by vandalism.

NR 811.64(4)(d) (d) Ground level structures.

NR 811.64(4)(d)1. 1. Overflow pipes shall terminate downward facing 90-degrees at a minimum of 12 to 24 inches above the final graded ground surface.

NR 811.64(4)(d)2. 2. The overflow shall be screened with 24-mesh corrosion resistant screen installed within the pipe at a location least susceptible to damage by vandalism.

NR 811.64(4)(d)3. 3. Each reservoir chamber that can be isolated from the rest of the reservoir so that it can remain in service while other chambers are out of service shall be provided with its own overflow pipe terminating outside the reservoir in accordance with the requirements of subds. 1. and 2.

NR 811.64(5) (5) Inlet-outlet piping. Inlet and outlet piping to a storage structure shall meet all the following requirements:

NR 811.64(5)(a) (a) Pressure requirements. Inlet and outlet piping from a storage structure shall be under positive pressure at all times wherever practical and in conformance with s. NR 811.37 (1). The department may approve inlet piping that is not under positive pressure at all times on a case-by-case basis where the piping is exposed and located above grade.

NR 811.64(5)(b) (b) Pipe sizing. Piping shall be sized to accommodate design fill and removal rates including considerations for future improvements.

NR 811.64(6) (6) Bypass piping.

NR 811.64(6)(a) (a) Groundwater facilities. If the water system design is such that all water passes through one ground reservoir, there shall be bypass piping from the well pumps to the high lift pumps to allow the reservoir to be taken out of service for cleaning and maintenance. The department may waive this requirement if the well pumps can provide sufficient volume and pressure directly to the distribution system, if the well pumps and high lift pumps are greatly different in capacity, or if the reservoir is divided into multiple cells which can be independently removed from service. If CT is required, the department will approve bypass piping around reservoirs only if the required minimum CT can be met with the reservoir chamber or chambers out of service.

NR 811.64(6)(b) (b) Surface water facilities. If the water treatment plant design is such that all water passes through one ground reservoir, bypass piping or multiple cells shall be installed to allow the reservoir to be totally or partially taken out of service for cleaning and maintenance. The design shall provide for maintaining the required minimum CT while the reservoir is totally or partially out of service.

NR 811.64(7) (7) Access. Water storage structures shall be designed with reasonably convenient access for cleaning and maintenance. Manholes installed above the waterline shall meet the following requirements:

NR 811.64(7)(a) (a) Elevated storage structures and reservoirs covered by inhabitable structures. Manholes on elevated tanks, standpipes and reservoirs covered by inhabitable structures shall be framed a minimum of 4 inches above the surface of the roof. Manhole openings shall be fitted with a solid watertight cover. Manhole covers for elevated tanks shall overlap the framed opening and extend down around the frame a minimum of 2 inches. A compressible gasket shall be provided so that when the cover is closed it will provide a water tight seal around the manhole opening.

NR 811.64(7)(b) (b) Ground storage structures. On ground level structures, manholes shall be elevated no less than 24 inches above the top or covering sod. Manhole openings shall be fitted with a solid watertight cover that overlaps the framed opening and extends down around the frame a minimum of 2 inches. A compressible gasket shall be provided so that when the cover is closed it will provide a water tight seal around the manhole opening.

NR 811.64(7)(c) (c) Locks. Overlapping interior and exterior manhole covers shall be locked at all times except when being used by authorized personnel.

NR 811.64(7)(d) (d) Other openings. All other manholes, openings, or access ways shall be provided with watertight, bolted, and gasketed covers.

NR 811.64(8) (8) Vents. Water storage structures shall be vented to the atmosphere. Vent installations shall meet the following requirements:

NR 811.64(8)(a) (a) General requirements.

NR 811.64(8)(a)1. 1. The overflow pipe shall not be considered a vent.

NR 811.64(8)(a)2. 2. Open construction between the sidewalls and the roof to act as a vent is not allowed.

NR 811.64(8)(b) (b) Exclude contamination. Vents shall be constructed to:

NR 811.64(8)(b)1. 1. Prevent the entrance of surface water, rain and snow as applicable.

NR 811.64(8)(b)2. 2. Exclude birds and animals.

NR 811.64(8)(b)3. 3. Exclude insects and dust to the extent this can be done while providing effective venting.

NR 811.64(8)(c) (c) Elevated tanks and standpipes. Vents installed on elevated tanks and standpipes shall terminate with a mushroom cap constructed with the opening at least 4 inches above the roof and shall be provided with a 4-mesh outer screen and 4- to 24-mesh inner screen constructed of corrosion resistant material installed within the pipe at a location protected from the environment. The mushroom cap shall be provided with an automatically resetting pressure-vacuum relief frost-proof mechanism. The skirted sides of mushroom caps shall totally cover any screens when viewing the cap from the side.