Effluent sewer
Effluent sewers also currently serve fewer people than septic systems, which also use septic tanks, but simply dispose of the effluent by draining it into a leach field. About one quarter of United States homes dispose of their wastewater with septic tanks. However, effluent sewers are being looked at as a sewage treatment solution in areas where gravity sewer systems are not well-suited or when the high capital cost to build a gravity system is prohibitive. Areas that are less than ideal for gravity systems include areas that are large, but extremely flat and areas that require long-distance pumping, such as where homes are widely spread out or when several small villages or towns connect their sewage systems so that a centralized plant can be built.
Tankhouse
There are far more tankhouses in California than in any other state, and they most probably originated in California. A tankhouse was built in Mendocino, California, in 1857 and many tankhouses in a variety of designs are still standing in that village. Tankhouses can be found in most of the state's 58 counties, wherever there was water not more than 50 feet or so below the surface. Probably after transcontinental and branch railroads were completed, tankhouses were built in other western states, the midwest, and even in the east.