(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.
(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:
(13) STEP system equipment.
(14) Housing for on-site mechanical equipment and any associated control mechanisms must be:
(15) A vault, chamber, wet well, or other structure used to contain wastewater must be:
(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:
(10) An isolation valve must be:
(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.
(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