on is limited. The problem is the tremendous expense of frequent pumping, and the tendency of users to allow them to overflow. Use of holding tanks makes the most sense for temporary situations, emergency situations, and short-term seasonal applications. You can cap off the outlet of a newly installed septic tank and use it as a holding tank while you wait for the bank to finance the new drain field or for the septic tank contractor to fix the old drain field. If you use very little water at your mountain cabin, you may have to get your holding tank pumped only once a year. This is one of the more common uses of the holding tank. But that one trip by the septic tank pumper may cost $150 or more. ONSITE WASTEWATER DISPOSAL Table 7.3 Wastewater Characteristics Suspended Fecal Total Solids Coliform Nitrogen Source % Volume (mg/L) (no./100 mL) (mg/L) Toilet Bathing Kitchen sink Clothes washer Other Garbage disposal Total grey water Total combined water Before you decide to install a holding tank, consider its value compared to its long-term expense. Find out if a pumper truck will be available, and if so, how much a trip to your holding tank will cost. A variation of holding tank use is where it is used to contain only a part of the wastewater generated. For example, if toilet wastes are piped to a holding tank and the rest of the wastewater disposed of in a conventional drain field, then the amount of nitrogen pollutants discharged is reduced by about 70%. Table 7.3 shows the percent volume and approximate concentration of some pollutants in vari- ous components of household wastewater. These numbers were taken from a number of sources and often represent rough averages of highly variable values. Where toilet wastes are piped to a holding tank, it is highly recom- mended that toilets using a very low volume of flush water be used. Toilets are available which use as little as two quarts to a gallon of water per flush. Low flush-volume toilets don't transport solids through standard (4-in.) drainpipe as well as the th