1. (a) Velocities.

   1. (1) A force main must be a minimum of 4.0 inches in diameter, unless it is used in conjunction with a grinder pump station.
   2. (2) For a duplex pump station, the minimum velocity is 3.0 feet per second with one pump in operation.

   3. (3) For a pump station with three or more pumps:

      1. (A) the minimum velocity in a force main is 2.0 feet per second with only the smallest pump in operation; and
      2. (B) a minimum flushing velocity of 5.0 feet per second or greater must occur in a force main at least once daily.
   4. (4) The report must certify that a pipeline with a velocity greater than 6.0 feet per second can withstand high and low negative surge pressures in event of sudden pump failure.

2. (b) Detention Time.

   1. (1) A force main detention time calculations must be included in the report.
   2. (2) The force main detention time calculations must be performed using a range of flow rates that represent the flows expected to be delivered to a force main by an upstream pump station during any 24-hour period.
3. (c) Water Hammer. A force main design must include surge control measures to manage pressure due to water hammer that may exceed the working strength of a force main pipe.

4. (d) Connection to Gravity Main.

   1. (1) A force main must terminate in an appropriate structure and either at a manhole on the wastewater collection system or at a wastewater treatment facility.
   2. (2) The discharge end of a force main inside a manhole must remain steady and produce non-turbulent flow.
   3. (3) A receiving wastewater collection system must accept the maximum pump discharge without surcharging.
5. (e) Pipe Separation. A separation distance between a force main and any water supply water pipe must meet the minimum separation requirements established in §217.53(d) of this title (relating to Pipe Design).

6. (f) Odor Control.

   1. (1) A force main must terminate below a manhole invert with the top of the pipe matching the water level in the manhole at design flow.
   2. (2) A force main must be designed to abate any anticipated odor.

7. (g) Air Release Valves in Force Mains.

   1. (1) Any high point along the vertical force main alignment must include an air release valve or a combination of air release and air vacuum valves.
   2. (2) An air release valve must have an isolation valve between the air release valve and the force main.
   3. (3) An air release valve must be inside of a vault that is at least 48 inches in diameter and has a vented access opening at least 30 inches in diameter.
8. (h) Valves. A force main must have valves spaced at no more than 2,000 foot intervals to facilitate initial testing and subsequent maintenance and repairs.

Source Note:The provisions of this §217.67 adopted to be effective August 28, 2008, 33 TexReg 6843.