mps, since there is less that can go wrong with them and they consume no energy. ONSITE WASTEWATER DISPOSAL Outdoor Receptacle Threaded Union with Two Circuits Conduit Gate Valve To Drainfield From Septic Tank Anti-Siphon Hole Pump Control High Water Level Alarm float "Pump on " float "Pump off" float Submersible Concrete Block Figure 4.6 Typical dosing chamber. Overflow Discharge Figure 4.7 Automatic dosing siphon. WASTE PROCESS Process As effluent overflows into the septic tank outlet, the liquid level in the dosing chamber rises. When the level reaches the point where the "pump on" switch is set, a pump-generally a sewage rated sub- mersible pump-evacuates the effluent to the disposal field. When the level of liquid in the dosing chamber declines to the "pump off" level, a switch stops the pump. A dosing siphon operates without any moving parts. As liquid in the dosing chamber rises above the siphon, the air trapped in the siphon's bell is compressed and forces the water in the "U" trap down the long leg of the trap. As the air reaches the bottom of the "U," it rushes up the short leg, and the water drawn after it starts the siphon action. Flow continues until the water level is lowered to below the bottom of the bell and the siphon is interrupted. The volume of the dose is fixed by the design. Design Figure 4.6 shows the details of a dosing chamber using a submers- ible pump. Both components must be sized independently. The chamber design is the same for any of the four applications. The pump specifications differ depending on the method of disposal. Dosing chamber capacity for chambers with pumps should be the sum of (1) the daily wastewater design flow, (2) the space between the "on" level and the alarm set level, (3) one dose of wastewater (the space between the "pump on" and "off" levels), and (4) the permanent reservoir in which the pump rests. The space above the high water alarm is to allow time for repair should the pump fail (they always fail on weekends), should a power outage occur, or should probl