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RULE §217.97Pressure Sewers

(a) Pumps. A pressure sewer system must include a grinder pump or a septic tank effluent pump (STEP).

(b) Exceptions. Except where this section specifically states otherwise, the requirements of this section apply to both grinder pumps and STEPs.

(c) Service Pipe Requirements.

  (1) A pressure sewer service pipe that is buried less than 30 inches below ground must incorporate a check valve and a fully closing gate or ball valve at the junction of a collection pipe and a service pipe to allow isolation of the service pipe.

  (2) A check valve must allow an unencumbered flow when fully open.

  (3) A valve must be made of corrosion-resistant material and must have a position indicator to show its open and closed position.

  (4) The minimum size service pipe for an equivalent dwelling unit (EDU) is 1.25 inches.

  (5) The minimum size service pipe for a multiple equivalent dwelling unit (MEDU) is 1.5 inches.

  (6) A junction to collection pipes must be made with a tee or service saddle and may use solvent weld fittings.

  (7) The diameter of a service pipe must be no greater than the diameter of the collection pipe to which it is connected.

  (8) Material used in a service pipe must have performance characteristics that are at least equivalent to American Society for Testing and Materials (ASTM) D 2241 Class 200 polyvinyl chloride (PVC) pipe.

(d) On-Site Mechanical Equipment Requirements.

  (1) Pump discharge rates must allow the capacity of the pump and the volume of the wet well dedicated for flow attenuation and storage to accommodate the expected peak flow.

  (2) A single pumping unit may be used for an EDU. The engineering report must include an analysis that justifies the size of the selected pump(s).

  (3) An MEDU must be served by at least two pumps capable of pumping the peak flow with the largest pump out of service. The engineering report must include an analysis that justifies the size of the selected pumps.

  (4) The calculations in the engineering report must show that all lift stations and pump chambers are protected against buoyancy forces.

  (5) Control panels for all pumps must be at least 2.0 feet above the ground floor elevation of the structure being served by the equipment.

  (6) All pipes and appurtenances within a wet well must be corrosion-resistant.

  (7) A wet well must include an audiovisual alarm system.

    (A) An alarm for an EDU must activate at the high water level specified in the engineering report, plans, or specifications for the project.

    (B) An alarm for an MEDU must activate in the event of unit failure or a high water level.

  (8) An EDU wet well must have a reserve volume of at least 100 gallons after the activation of a high water alarm.

  (9) The reserve volume of an MEDU wet well must equal the volume accumulated during an average two-hour period or 100 gallons, whichever is greater.

  (10) A pump located in a STEP chamber that is integrated with an interceptor tank may use the reserve volume of the interceptor tank for the required reserve volume.

  (11) A housing that contains mechanical equipment or controls must be watertight if immersion of the mechanical equipment or controls would cause failure.

  (12) A control panel or other electrical enclosure must:

    (A) be constructed of corrosion-resistant materials;

    (B) be watertight;

    (C) prevent the migration and venting of odor to the panel or enclosure;

    (D) prevent the migration and venting of corrosive or explosive gases to the panel or enclosure; and

    (E) bear the seal of the Underwriter Laboratory, Inc. or comply with the National Fire Protection Association 70 National Electrical Code®.

  (13) STEP system equipment.

    (A) A pump used in a STEP system may be housed either in an interceptor tank or in a separate stand-alone unit.

    (B) A pump housed in the interceptor tank of a STEP system must be located in separate chamber from the influent chamber.

    (C) The water level in a STEP system pump chamber must not affect the water level in the interceptor tank, to prevent the disturbance of settleable and floatable solids in the interceptor tank.

    (D) A design that allows a variable liquid elevation in an interceptor tank is prohibited.

  (14) Housing for on-site mechanical equipment and any associated control mechanisms must be:

    (A) lockable and tamper-resistant;

    (B) constructed of corrosion-resistant material; and

    (C) designed to last at least 50 years.

  (15) A vault, chamber, wet well, or other structure used to contain wastewater must be:

    (A) watertight;

    (B) able to withstand any expected structural loading;

    (C) constructed of corrosion-resistant material; and

    (D) designed to last at least 50 years.

(e) Discharge Pipe Requirements.

  (1) A discharge pipe and connections used to join on-site mechanical equipment to a service pipe must be pressure rated at a minimum of 2.5 times the maximum system design pressure.

  (2) Pipe material and valves must be corrosion-resistant.

  (3) A discharge pipe for a pressure system must include a check valve, a pipe union, and a full closing gate valve or ball valve. A check valve must precede a full closing gate valve.

  (4) A ball or gate valve must have a position indicator to show its open and closed positions.

  (5) A valve used at an MEDU must be located in a valve box separate from the on-site mechanical equipment.

(f) Collection System Design.

  (1) The velocity of wastewater in a grinder pump pressure system main pipe must reach at least 3.0 feet per second at least once per day.

  (2) The velocity of wastewater in a grinder pump pressure system main pipe must not be less than 2.0 feet per second nor exceed 8.0 feet per second.

  (3) The velocity in a STEP system main pipe must reach at least 1.0 foot per second at least once per day.

  (4) A collection system head loss calculation must use a Hazen-Williams "C" factor appropriate to the pipe material. The use of a "C" factor greater than 140 is prohibited.

  (5) The pipe used in a pressure collection system must be at least 1.5 inches in diameter.

  (6) Pipe material must have the performance characteristics at least equivalent to ASTM D 2241 Class 200 PVC pipe.

  (7) A pipe equal to or greater than 3.0 inches in diameter requires elastomeric pipe joints.

  (8) A pumping unit affected by less than full flow conditions must incorporate an anti-siphon device.

  (9) An isolation valve must be located at:

    (A) each intersection of a collection system main pipe;

    (B) both sides of a stream crossing;

    (C) both sides of an area of unstable soil; and

    (D) maximum intervals of 2,500 feet.

  (10) An isolation valve must be:

    (A) a resilient seated gate valve or ball valve with a position indicator;

    (B) constructed from corrosion-resistant materials; and

    (C) located in a locked valve box.

  (11) Each peak in elevation and each location where air may accumulate due to a difference in flow conditions requires a wastewater air release valve.

    (A) A valve orifice must be at least 0.25 inches in diameter.

    (B) An air release valve within 50 feet of a residence or building must control odor. An owner shall implement odor control measures necessary to prevent a collection system from becoming a nuisance.

  (12) When intermediate pumping of wastewater is required, the design of a collection system lift station must meet the requirements of Subchapter C of this chapter (relating to Conventional Collection Systems).

Source Note: The provisions of this §217.97 adopted to be effective August 28, 2008, 33 TexReg 6843; amended to be effective December 4, 2015, 40 TexReg 8254

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