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PLUMBING SYSTEM INSPECT DIAGNOSE REPAIR
AGE of PLUMBING MATERIALS & FIXTURES
AIR DISCHARGE at FAUCETS, FIXTURES
ANTI SCALD VALVES
ANODES & DIP TUBES on WATER HEATERS
BACKUP PREVENTION, SEPTIC
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BACKWATER VALVES, SEWER LINE
BATH & KITCHEN DESIGN GUIDE
CHEMICAL CONTAMINANTS in WATER
CHEMICAL ODOR SOURCES
CHLORINE IN DRINKING WATER
CLOGGED DRAIN DIAGNOSIS & REPAIR
DEBRIS in WATER SUPPLY, Water Heater
DEPTH of SEPTIC TANK
DRAIN & SEWER PIPING
FAUCETS & CONTROLS, KITCHEN & BATH
FAUCETS, OUTDOOR HOSE BIBBS
FLOOD DAMAGE ASSESSMENT, SAFETY & CLEANUP
FLOOR DRAIN / TRAP ODORS
FLUSHOMETER VALVES for TOILETS URINALS
GAS PIPING, VALVES, CONTROLS
GALVANIC SCALE & METAL CORROSION
HARD WATER - SOFTENERS
HEAT TAPES, Heat, Insulation prevent Freeze-Up
LEAD POISONING HAZARDS GUIDE
LEAD IN DRINKING WATER, HOW to REDUCE
METHANE GAS SOURCES
MIXING / ANTI-SCALD VALVES
MUNICIPAL WATER PRESSURE IMPROVEMENTS
NOISE / SOUND DIAGNOSIS & CURE
ODORS GASES SMELLS, DIAGNOSIS & CURE
ODORS IN WATER
ODORS, SEPTIC or SEWER
ODORS SEWER GAS in COLD WEATHER
ODORS, SULPHUR SMELL SOURCES
ANIMAL or URINE ODOR SOURCE DETECTION
PIPING IN BUILDINGS, Clogs Leaks Types
PLUMBING FIXTURES, KITCHEN, BATH
PLUMBING NOISE TRANSMISSION CONTROL
PLUMBING VENT DEFINITIONS & CODES
PLUMBING VENT DEFECTS & NOISES
PUMPS USED in BUILDINGS
PUMPS, WATER REPAIR
RELIEF VALVE LEAKS
RELIEF VALVE, TP VALVE, BOILER
RELIEF VALVE, TP VALVE, STEAM BOILER
RELIEF VALVE, WATER HEATER
RELIEF VALVE, WATER TANK
REPAIR BURST LEAKY PIPES
METHANE GAS HAZARDS
SEPTIC SYSTEM INSPECT DIAGNOSE REPAIR
SHUTOFF VALVE LOCATION, USE
SULPHUR & SEWER GAS SMELL SOURCES
SWEATING (CONDENSATION) on PIPES, TANKS
TOILETS, INSPECT, INSTALL, REPAIR
WATER, WELLS, WATER TANKS: TESTING GUIDE
WATER PRESSURE LOSS DIAGNOSIS & REPAIR
WATER PUMPS & TANKS
WATER SOFTENERS & CONDITIONERS
WATER SOURCE ALTERNATIVES
WATER SUPPLY & DRAIN PIPING
WATER SHUTOFF VALVE LOCATION, USE
WATER SHUTOFF VALVE, WELL PUMP
WATER TESTS, CONTAMINANTS, TREATMENT
WELLS CISTERNS & SPRINGS
WINTERIZE A BUILDING
Grease interceptors: this article describes the different types of grease interceptors or grease traps used to prevent drain & sewer system clogging by catching & permitting the removal of FOG (fats, oil, grease) from a building's plumbing system.
The article describes traditional gravity and baffle operated grease traps, hydromechanical grease traps, and automatic grease removal units or AGRUs. Sources for grease interceptor installation, specifications, maintenance, & building codes as well as producers & sources of these grease interceptor or grease trap products are included.
Page top photo: a traditional baffle and gravity type grease interceptor produced by Atlantic Metal Works (formerly Prima Supply).
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Fats, oils, and grease that are poured down building drains cause serious clogs in normal drain traps, drain piping, sewer piping and even public sewers & pumping stations. Fats, oils and grease, referred to in plumbing trades as FOG have been cited for as causing more than sixty percent of public sewer backups in New York City, at an annual cost of $4.65 million in 2013. (Gregory, The New York Times, 2014).
Illustrated at left: Zurn's Z1192 Grease Recovery Appliance (see AGRU below).
[Click to enlarge any image]
Types of Grease Interceptors or "grease traps"
Grease traps separate fats, oils, and grease from wastewater using one of several methods:
Watch out: some municipalities permit only AGRUs in new installations, and no longer permit passive style grease traps such as the gravity traps described just below. Quoting:
Shown at left: a gravity & baffle type grease trap produced by Atlantic Metal Works (formerly Prima Supply).
An excellent explanation of grease traps or interceptors is provided by a guidance document provided by the Carrolton Tx. government (2012) from which we quote:
FOG Grease Trap Size Requirements
The size required for a grease interceptor or grease trap is specified in the Uniform Plumbing Code (UPC). Typically local or municipal regulations indicate that grease trap size requirements depend of course on the volume of fats and oils passing into the drain system. Typically municipal codes regulating grease interceptor installation give general guidelines such as light or heavy food preparation, and additional capacity guidelines are given by the grease trap manufacturer's installation specifications (referred-to below). Typically the grease interceptor capacity required is specified as one of three categories:
Grease Trap Cleaning & Maintenance Requirements
The cleaning frequency depends on grease interceptor size or capacity, type, wastewater flow, and local regulations. For example, a community may specify that an AGRU must be "cleaned per the manufacturer's specifications", or that an existing (not permitted in new installations) passive style grease trap will be cleaned every two weeks, or at an interval specified by a local authority, or as follows:
Note: Additives, treatments, and enzymes are not required for grease traps and are prohibited in some municipalities. Quoting:
Grease Trap Waste Disposal
The grease interceptor codes & specifications we reviewed were mostly silent on this topic, but those that did discuss grease disposal suggested bagging the grease or other trap or interceptor debris in heavy plastic garbage bags for disposal as food waste.
Speaking of disposing of grease interceptor waste reminds installers of the importance of making the grease interceptor easily accessible. A reader who asked us about installing a grease trap in a 25-foot deep manhole where a sump or ejector pump system was in use had perhaps not imagined the service person having to lug a 25 or 50 pound bag of grease waste up a ladder.
FOG Grease Trap Location Requirements
For a grease interceptor to work properly it must be located sufficiently far from the hot water source that the wastewater entering the trap will be cool enough that the trap can in fact do its job: trapping fats, oils and grease passing by. A grease trap must be accessible for regular inspection (through a wastewater sampling well) and cleaning.
The model code we cite below specifies the following:
Other Commercial Facility Plumbing Traps & Filters
Other commercial facilities are required to install FOG interceptors, debris and grit traps, or lint interceptors, such as automobile repair shops, car washes, and commercial laundries.
Automotive repair facilities are typically required to install a grit and oil trap and separator on their drain with a typical minimum capacity of 50 gallons for the first 100 sq. ft. of area drained (such as the garage floor) and an additional one cubic foot of capacity (7.5 gallons) per additional 100 sq .ft. of floor area.
Commercial laundries may be required to install suitable filters and traps also intended to protect the sewer system but designed to capture other clog-source materials such as lint traps. is specified in the Uniform Plumbing Code (UPC) Appendix H contains the formula for calculating a lint filter size for commercial facilities.
How are Grease Clogs Cleared?
In municipal and building plumbing systems when a grease-clogged drain line or sewer line are discovered to have been clogged by FOGs experts use high powerd vacuums or high pressure water to attempt to clear the drain. Simple mechanical drain cleaning that is used to clear more solid obstructions may be ineffective.
References & Sources for FOG Grease Interceptors & Traps, Codes, Specifications, Remedies
Grease Interceptor Suppliers
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