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SEPTIC SYSTEM INSPECT DIAGNOSE REPAIR
SEPTIC CARE INSTRUCTIONS
SEPTIC D-BOX INSTALL REPAIR
SEPTIC DRAINFIELD FAILURE DIAGNOSIS
SEPTIC DYE TEST PROCEDURE
SEPTIC FAILURE SIGNS
SEPTIC INSPECTION & TEST GUIDE
SEPTIC LIFE EXPECTANCY
SEPTIC SUPPLIES & PARTS
SEPTIC SYSTEM DESIGN ALTERNATIVES
SEPTIC SYSTEM DESIGN BASICS
SEPTIC SYSTEMS, HOME BUYERS GUIDE to
SEPTIC SYSTEM SAFETY WARNINGS
SEPTIC TREATMENTS & CHEMICALS
SEWAGE BACKUP PREVENTION
SEWAGE EJECTOR / GRINDER PUMPS
SEWER GAS ODORS
SEWER LINE REPLACEMENT
SINKHOLES, WARNING SIGNS
SOAKAWAY BED FAILURE DIAGNOSIS
SULPHUR & SEWER GAS SMELL SOURCES
TOILETS, INSPECT, INSTALL, REPAIR
TRAPS on PLUMBING FIXTURES
TREATMENTS & CHEMICALS, SEPTIC
VIDEO GUIDES: Septic Videos
WATER CONSERVATION MEASURES
WATER SOFTENERS & CONDITIONERS
WATER SUPPLY & DRAIN PIPING
WATER, WELLS, WATER TANKS: TESTING GUIDE
WASHING MACHINES & SEPTIC SYSTEMS
WASTEWATER TREATMENT BASICS
WINTERIZE A BUILDING
Sand filter septic design details: this document discusses design and use of septic media filters using sand. When using a septic media filter system, effluent treatment is by both actual filtration and ultimately by a biochemical process as the filter "matures" and includes its own biomass. This is particularly true of sand-bed filter septic systems which also often use a recirculating sand bed design to move septic effluent multiple passes through the sand filter system.
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The septic tank which receives waste from the building should have either two compartments, or two tanks in series are used.
A gas baffle on the tank outlet is recommended (NY State Wastewater Treatment Standards) to reduce the chances of a periodic bolus of gas forming in the bottom of the tank and forcing solids into the sand media.
When a sand filter system is used, effluent is periodically distributed out of the septic tank and over the surface of a constructed bed of sand through a network of perforated pipes. Collector pipes below the sand pick up effluent after it has filtered through and been treated by (the biomat formed on) the sand filter.
Effluent dosing is by pressure-fed perforated lines of 1.5" to 3" diameter, or by siphon dosing using a 3" to 4" diameter effluent line. New York requires that the system is dosed at least three times daily. Dosing should not exceed 1.15 gallons/day/sq. ft. of media area.
Various texts cite the critical importance of selecting the proper sand for a septic media filter. New York's standard specifies a sand grain size of 0.25 to 1.0 mm; if nitrification is required (which may be specified by the local health department), the grain size is larger, 0.5mm to 1.0 mm., and all sand is passed through a 1/4" sieve and must be uniform to a coefficient of 4.0.
The effluent collector pipes below the sand bed discharge the treated effluent to an absorption system such as a drain field placed below the original ground level or possibly into a raised bed or mound system. The raised bed or mound receiving the treated effluent may itself be constructed of sand or other fill material with a percolation rate of not faster than 5 minutes per inch.
Typical sand filter construction (NY State Wastewater Standards) involves an excavated bed area which is filled in layers of material as follows (bottom up):
Sand filter problems: keep deep rooting plants, surface runoff, and heavy traffic (that could compact the media) off of the system. Don't block air movement over the surface of the system with buildings or plantings.
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Technical Reviewers & References
More Reading on Sand Filter Systems
Using a Sand Bed Effluent Disposal System as a Component of Alternative Septic Systems for Difficult Sites. This document includes the NYS Appendix 75-A section on sand filter beds (next citation) as well as sand filter bed design comments and advice from other experts
SAND FILTER SEPTIC DESIGN SPECIFICATIONS - New York State Appendix 75-A Design Details for Intermittent Sand Bed Filter Septic Systems
References for this Septic Media Filters Discussion
Design Manuals for Septic Systems
Onsite Wastewater Disposal Books