Wisconsin Administrative Code
Department of Natural Resources
NR 800 - Environmental Protection - Water Supply
Chapter NR 812 - Well Construction And Pump Installation
Subchapter III - Requirements for New Pump Installations and Water Treatment
Section NR 812.33 - Water storage vessels

Universal Citation: WI Admin Code ยง NR 812.33

Current through August 26, 2024

The department recommends that pressure tanks be sufficiently sized to provide the minimum pump run time recommended by the pump manufacturer.

Note: Community water systems regulated under ch. NR 811 are required to have a gross pressure tank volume of 10 times the pump capacity.

(1) PRESSURE TANKS.

(a) General. Tanks relying on expansion of a flexible membrane within a restricting container, rather than on a water to air interface to provide pressure in the water system, may be used. All pressure tanks for storing potable water under pressure, including those having an air space for expansion, shall be identified by seal, label or plate indicating the manufacturers name and model number and shall meet the following specifications:
1. Pressure tanks to be buried shall be constructed of steel, fiberglass or other comparable non-metallic composite material. Steel tanks with metallic discharge piping, meeting the requirements of s. NR 812.28, shall be used in contaminated soil areas. Steel tanks to be buried shall have a minimum wall thickness of 0.25 inches. Fiberglass or other non-metallic tanks to be buried shall have the structural strength to prevent collapse of the tank. Manufacturer's instructions shall be followed. All buried tanks shall be back-filled in place with sand, compacted in place. Steel pitless receiver tanks, when they are part of approved pitless units attached directly to the well casing pipe, shall also have a minimum wall thickness of 0.25 inches. Any air unloader pipe, tank air valve or any other pipe connection extending up to the ground surface shall be steel pipe meeting the requirements of s. NR 812.28 and shall terminate at least 12 inches above ground grade.

Note: The department recommends that a surface air check kit be installed for a buried pressure tank to check, maintain and adjust the air pressure pre-charge of the tank. Also, in uncontaminated soil areas, pipe and pipe connections to the tank should be made with flexible pipe and fittings meeting the requirements of s. NR 812.28 to minimize strain or pressure on the tank or the tank fittings.

2. Pressure tanks having a gross volume in excess of 500 gallons, and not having a water to air interface bladder, shall have the following:
a. If the tank is buried, all electrical controls extended to at least above ground grade.

b. Each tank shall have an access manhole, a drain, and pressure gauge, pressure relief valve, water sight glass and pressure or probe operated controls for the pumps.

c. An air compressor or other suitable means to add air to the tank.

d. Any interior protective materials including but not limited to liners, paints, coatings, or sealants shall be certified for potable water use under NSF Standard 61.

Note: The department recommends that the tank have bypass piping to allow operation of the system while the tank is being repaired or painted.

(b) Pressure tanks larger than 1,000 gallons gross volume. An approval shall be obtained for pressure tanks having a gross volume greater than 1,000 gallons. The department recommends that pressure tanks having a volume greater than 1,000 gallons be installed above ground. When approved, the tank shall be installed according to the requirements of par. (a). When tanks of this size are approved for burial, the head end of the tank shall be cradled in a basement wall or in the wall of an approved pit to provide access and shall be constructed to the specifications for pits described in s. NR 812.36 (2) to provide access to the head of the tank. The pit shall have other additional support cradles. Pitless receiver tanks having a volume greater than 1,000 gallons may be installed without an access pit.

(2) NONPRESSURE STORAGE VESSELS. Nonpressure storage vessels, designed as part of a potable water supply system, may not be installed without approval from the department under s. NR 812.09. Approval is required regardless of whether or not there is a free-air gap in the water inlet line upstream of the vessel. Vessel approval is based on methods of construction and sanitary provisions. The installation of a surge tank is exempt from this approval requirement.

(a) Surge tanks. Surge tanks shall meet the requirements for pressure tanks described in s. NR 812.33 (1).

(b) Reservoirs and elevated storage tanks. A reservoir may be constructed to store water if it is constructed above the groundwater level and in accordance with this paragraph and Figure 7 of ch. NR 812 Appendix.
1. 'General construction specifications.'
a. Gravity supply pipes shall be located entirely above grade and shall be conducted to the reservoir through the roof or through the curbing for the manhole. The overflow pipe described in subd. 1.b. may be installed at such a level to provide a free-air gap. Buried supply pipe shall be maintained under a continuous pressure head which is greater than the ground surface elevation.

Note: The department recommends that trees and shrubs not be planted within 25 feet of a reservoir.

b. An exposed overflow pipe shall be located just under the roof of the reservoir or outside the elevated storage tank and shall extend at least 8 feet away. The overflow pipe shall terminate with a downturned, screened elbow located at least 12 inches above ground grade. The pipe shall discharge onto a splash plate and have sufficient diameter to permit wasting water at a rate in excess of the inflow from the water source.

2. 'Steel construction specifications.' Steel reservoirs or elevated storage tanks shall meet the requirements of AWWA D100-84 for welded construction or AWWA D103-80 for bolted construction.

3. 'Access.' Water storage structures shall be designed with convenient access for cleaning and maintenance.

4. 'Concrete construction specifications.' Reservoirs constructed of concrete shall meet the following specifications:
a. The supply pipe and overflow pipe shall extend through the structure.

b. An impervious flexible water stop strip for wall construction joint and a reservoir drain facility shall be installed before the concrete is poured.

c. The floor of the reservoir shall be reinforced poured concrete with a thickness of at least 6 inches and shall have a curbing wall 6 inches high and 6 inches thick having a keyway or a flexible water stop strip for a construction joint with the walls.

d. The walls of the reservoir shall be reinforced poured concrete at least 6 inches thick and terminate above the established ground grade.

e. The roof shall be reinforced poured concrete at least 6 inches thick and shall extend at least 12 inches above established ground grade. An access manhole at least 20 inches in diameter or 20 inches square shall be constructed as an integral part of the roof. The manhole shall have a curbing wall extending at least 12 inches above the roof. The department recommends that the manhole shall be constructed entirely of 4-inch thick reinforced poured concrete, but may be fabricated of 1/4-inch steel or cast iron frame with a gasket and bolted cover. The curbing shall be provided with a snug fitting, overlapping cover with a minimum of 3-inch wide skirted sides. The department recommends that the cover be constructed with welded sheet steel, but may be constructed with reinforced poured concrete. Concrete shall be mixed according to the requirements specified in s. NR 812.11 (15) (e).

5. 'Location requirements.' A reservoir shall be located according to the requirements of s. NR 812.08, including the minimum separation distance requirements of s. NR 812.08 (4) established for existing or proposed potential sources of contamination.

(3) PAINTING AND CATHODIC PROTECTION. Metal surfaces of reservoirs or elevated storage tanks, to be in contact with potable water, shall be protected by paints, other protective coatings, or by cathodic protection except when documentation is provided to the department that the source water will not be aggressive or corrosive to the metal surfaces. Paint or coating systems shall conform with AWWA standard D102 and shall be NSF approved for use with potable water. When cathodic protection is to be provided, it shall be designed and installed by competent technical personnel. A copy of the AWWA standards are available for inspection at the office of the department of natural resources and the office of the legislative reference bureau, and may be obtained for personal use from AWWA, Inc., 6666 W. Quincy Avenue, Denver, Colorado 80235.

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