disposal field siphoning back to the dosing chamber. Correc- tion of the pump discharge capacity is necessary to accommodate this hole because effluent will be pumped through it while the pump is running. Add 2 gal per min, the approximate flow rate through this hole, to the desired delivery rate. A check valve should not be used unless absolutely necessary, since they tend to malfunction frequently. Use a check valve only if the drainback into the dosing chamber would be more than about one-fourth the dose volume, and then only if there is no danger of freezing. A very important point is to specify that the pump switching be entirely enclosed and sealed, or else located outside the dosing chamber. Unprotected switches will last about two weeks in the very corrosive environment inside the chamber. (Two weeks is also the expected lifetime of a pump that is rated for fresh water rather than sewage.) Further, a spark from a switch inside the chamber can cause an explosion. The "off" level should be above the submersible pump to ensure that it remains submerged. There are mechanical float switches (which may not allow suffi- cient "on-off" adjustment), diaphragm pressure switches (which tend to malfunction), mercury float switches (which seem to work quite nicely where the "on-off" distance is short), and magnetic level controls (the best and most expensive). Be sure that there is a threaded union in the effluent pipe to allow easy removal of the pump for servicing. A nylon rope attached to the pump allows removal without putting a strain on the PVC pipe. ONSITE WASTEWATER DISPOSAL Also, install a gate or ball valve in the effluent pipe to allow final pressure adjustments. The tank access lids should be watertight and about 6 in. above the ground surface. Buried dosing tanks tend to suffer from neglect more than do visible tanks. Those tanks that are hard to locate and which have access ports deeply buried tend to malfunction just before the start of ball games on TV. Power and control wires may be fed by conduit thr