kin of a carrot could harbor all kinds of nasty germs. Keep vehicles and heavy foot traffic off the site, and don't rototill the distribution system. Pump out both the septic tank and dosing chamber as needed. Check the pressure head and flush the laterals yearly. Make routine inspections of all system components and follow the pump manu- facturer's recommendations for pump maintenance. Also, turn valves occasionally to keep them from seizing and periodically check the operation of the high water alarm. If the pump fails to pump effluent to the field, the distribution pipes may be clogged. Try backflushing through the turn-ups. When you do this, don't attach a hose to the turn-up and then turn the water on. That would create a cross-connection and could result in pollution of the water system in your house. Put on your raincoat and hold the hose up against the open end of the turn-up. If back- flushing the distribution system doesn't work, you might try push- ing a flexible cable through the distribution pipe. Before replacing any components in the dosing chamber, make sure that the problem is not with the electrical controls or the floats. Start ONSITE WASTEWATER DISPOSAL checking at the pump, then go to the pump switch, and SO on, until you isolate the problem. Then repair or replace the appropriate compo- nents. SAND FILTERS Application Sand filters are used in swimming pool recirculation systems and municipal water and wastewater systems to filter and cleanse water. They can be very effective in cleaning wastewater onsite as well, if the filter is properly designed and proper sand is used. There are several kinds of sand filters for wastewater treatment and disposal, each suited to a particular application. One commonly used type is the sand filter trench. This type of sand filter closely resembles a conventional absorption trench, but contains a layer of sand in the trench. This system is used where the surrounding soil is too coarse to provide adequate filtration before the effluent reaches a limiting zone,