A septic system, or on-site sewage facility (OSSF) is a term used to describe any wastewater system that is designed to treat and dispose of effluent on the same property that produces the wastewater.
There are many different types of septic systems but virtually all consist of a combination of a tank and a leaching system or drainage field. Utilizing natural waste recycling processes, the septic tank retains the waste water and allows microorganisms to decompose and break down most of the solids into a liquid called effluent. From the septic tank the decontaminated effluent is drained and disbursed through the leach field and into surface water or water wells.
Cost varies tremendously with the soil conditions, topography, and amount of use. Residential systems in Central Texas can range from $6,000 to as high as $60,000 for large scale commercial systems. There is no such thing as one size fits most or even an average cost. The current range for installation cost for residential systems in the Central Texas area is $10-20,000 with certain difficult areas occasionally exceeding this price range. A replacement system is typically more costly than the original system or a comparable new system.
The two main treatment processes are anaerobic and aerobic systems. Anaerobic septic systems are the most common type of system, functioning in the way discribed above (see: How does a septic system work?)
Aerobic septic systems involve exposing the effluent to oxygen in a suspended-film reactor after premptive treatment from the septic tank. Biofilters, like aerobic systems function much like scaled down versions of municipal sewage treatmant plants. Most alternative treatment methods treat wastes after they exit the septic tank, and can be added onto a design as required by performance, wastewater characteristics and site conditions.
Common types of septic systems include: Conventional pits or trenches, Low Pressure Dose Trenches, Drip Emitters, Surface application, Mound septic systems, Evaporates, Sand Filters, Artificial Wetlands, Bio-Filters and many others.
There is no set answer for this question. Each site can have one or more types of systems which may be suitable. The choice of system type is where an experienced designer can add critical value to making the proper selection. In general, the least complex design is the best starting point. All design possibilities should be considered and evaluated by the design professional on their individual merits, prior to making a final choice.
The answer to this question depends on the size and vollume of your septic system, though those in the regulatory and pumping industry recommend that the scum/sludge layer of the septic tank should never be permitted to fill more than 30% of the tank's vollume. To be on the conservative side, most tanks should be pumped every 2-3 years.
The size of the system varies with type of soils, type of system, location, and waste water generation. Residential systems are based on the potential number of people in the house, which is determined by the heated and cooled square footage and the number of bedrooms (any room with a door and a closet), whichever is the greater number. Commercial systems are based on both the volume of waste water and the characteristics of the waste water.
Yes! A more experienced designer will best determine the optimal system at the most reasonable cost for each site. Similar designs for the same site can have very different performance records and useful life spans. One system may experience problems in as little as two years while a more appropriate, better designed system can easily provide useful service for 15 years or more. If the price point system costs $8,000 and the better designed system costs $15,000 then the more expensive system costs only $1,000 a year while the poorly designed system costs $4,000 a year. Therefore you are then looking at a full replacement cost which will undoubtedly exceed the cost of a better designed system initially.
All systems are reviewed and inspected for minimum regulatory compliance by the State Designated Representative (jurisdictional authority). Unfortunately, this does not assure that the best possible system for a particular site is installed. A system can meet regulatory compliance and still be a very poor septic system. Typically, poor design equals unplanned and possibly major expenses for correction or replacement.
The first step is to select a designer/site evaluator. Then, exploratory holes are excavated in promising areas. The best location regarding soil and drainage is selected. A site plan and survey is needed; the more detail the better. Once this information is gathered and the use of the system or size of the house is defined, the design process begins. When the design and associated planning materials are complete, an application is made to the regulatory agency. The review process is thirty days (for Texas) and often final revisions are required prior to approval. During this time preliminary bids for installation may be sought. Final bids are submitted once permitting is approved.