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Vent to atmosphere

Strainer ^Diaphragm valve (three-way)

Combination air and vent line

-Gate valve

Shone check valve

Shone check valve

FIG. 7.12.7 Pneumatic ejector and associated piping.

-Gate valve

Shone check valve

Shone check valve

FIG. 7.12.7 Pneumatic ejector and associated piping.

plosion or gas buildup exists, and ventilation is extremely important.

When wastewater is pumped at high velocities or through long lines, the hammering caused by water can be a problem. Valves and piping should be designed to withstand these pressure waves. Even pumps that discharge to the atmosphere should use check valves to cushion the surge.

Bar screens and comminutors are not recommended, but for small centrifugal pump stations, they can be necessary.

Pump level controls are not fully reliable because rags can short electrodes and hang on floats. Purged-air systems

(air bubblers) require less maintenance but need an air compressor that operates continuously. Therefore, maintenance-free instrumentation must be provided.

Charts and formulas are available for sizing wet wells, but infiltration and runoff must also be considered.

Sump pumps, humidity control, a second pump with an alternator, and a pump hoisting mechanism are recommended.

Most states prefer dry-well designs.

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