Question? Just ask us!
Free Encyclopedia of Building & Environmental Inspection, Testing, Diagnosis, Repair
InspectAPedia ® Home
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
Septic tank floating scum layer thickness: this document explains the tool and the procedure for measuring the thickness of the floating scum layer in a septic tank as an aid in determining septic tank condition and whether or not the septic tank needs to be pumped and cleaned. We include descriptions of how to make septic sludge and scum measuring tools.
Whether your septic system is a conventional septic tank and drain field or soakaway bed, an above ground septic system, or even a sewage holding tank, pumping and inspecting the septic tank is a critical septic tank maintenance and septic system maintenance chore.
Green links show where you are. © Copyright 2014 InspectApedia.com, All Rights Reserved.
How to Measure the Scum layer thickness in a septic tank: How to measure the thickness of the floating scum layer in a septic tank
When the septic tank is pumped, measurements of the scum layer and sludge layer tell you the condition of the system. This procedure is modeled after the procedure described in classes for obtaining a Massachusetts Title 5 Septic Inspectors License. However other states and authorities describe a similar procedure. Some septic contractors have built and bring to the pumpout job their versions of the equipment described below.
The septic tank scum layer probe shown at left (courtesy USDA and US FPS) is also illustrated in a photograph just below.
Page top septic tank sketch courtesy Carson Dunlop Associates.
Septic tank scum layer thickness measurements (HOW TO MEASURE SEPTIC SCUM LAYER) and septic tank bottom sludge layer thickness measurements (HOW TO MEASURE SEPTIC SLUDGE LAYER), made or at least roughly estimated by the septic pumping contractor at the time that a septic tank is pumped, provide key information that permits the home owner to know
Watch out: Safety concerns when measuring septic tank scum and sludge levels: The procedure described below involves opening a septic tank and probing to determine the thickness of settled sludge in a septic tank and to measure the thickness of the floating scum layer in the tank. This procedure is dangerous, involving possible exposure to methane gas and possible risk of falling into a septic tank. The procedure should be performed by a qualified septic contractor. No one should open, inspect, or examine a septic tank while working alone.
Sanitary concerns when measuring septic tank scum and sludge levels: wear gloves when handling the septic probe and watch where you're swinging the pole around so as not to splash septage on your assistant (never work alone on septic systems). The equipment should be washed after use if it is to be retained for future use. Some septic contractors carry their poles in a long plastic-lined box which goes back on the truck.
How to Make the septic tank probe for measuring scum & sludge layer thickness
We recommend using 2" poly piping for this
purpose as it's easy to wash off. A simple door hinge is bolted to the end of the pipe and to the flapper board.
While some pumpers let the board float to feel the points described below, I've seen others who used a board which was fixed at a 90-deg. angle to the pole. (See illustration above).
Also see TUBE for MEASURING SCUM & SLUDGE for a tool that can make both scum and sludge thickness measurements with a single device. For deep or hard to access or commercial septic tanks that may need close monitoring, see ELECTRIC MONITOR for SCUM & SLUDGE and also take a look at Other Measures Scum / Sludge
A similar sludge & scum measuring procedure is provided in Septic Tank/Soil-Absorption Systems: How to Operate & Maintain [ copy on file as /septic/Septic_Operation_USDA.pdf ] - , Equipment Tips, U.S. Department of Agriculture.
The floating scum layer in a septic tank includes oil and grease which, if pushed into the leach field, will clog that component of the septic system.
Oil and grease are particularly harmful to the aerobic portion of septic effluent treatment in the soil absorption system.
Therefore we want to clean the septic tank if the scum layer has thickened to the point of risking pushing grease and oil out of the tank.
The septic tank needs to be pumped when the floating scum layer has accumulated to reach 3 inches of the bottom of the outlet baffle or tee.
See SEWAGE LEVELS in SEPTIC TANKS for details on normal and abnormal levels and what they mean.
WHEN TO PUMP - 3 Rules on How thick can the septic tank sludge and scum layer be before septic tank cleaning is needed?
The following is an excerpt from What Scum Sludge Thickness = Pump Needed.
"Generally at a two year interval for septic tank pumping service the average septic tank in these size ranges will have a 400 mm scum layer with about a 200 mm sludge layer. With an average depth of 1600 mm, the solids content is about 600 mm thereby reducing the settling time by nearly 40%.
Similar rules of thumb offered by USDA on how much sludge or scum mean the septic tank needs cleaning include:
Watch out: Don't wait too long before removing septic scum and sludge People who wait until their septic system stops working due to a clogged or over-filled (with sludge and scum) septic tank have waited too long. As the bottom sludge layer increases in thickness, and as the top septic scum layer increases as well, the remaining "net free area" or "effective septic tank volume" of effluent in the tank is reduced in volume.
When a septic tank is operating with a low volume of "net free area" of septic effluent, the system lacks adequate volume to provide adequate settlement time - time needed for sludge to settle to the tank bottom and scum to coagulate at the tank top (EFFLUENT RETENTION TIME) .
In this circumstance, although drains in the building seem to be just fine, the septic tank effluent is remaining in a constant state of stirred-agitation. In turn, that means that the system is pushing floating debris into the leach field or other absorption system.
Pushing grease, scum, and small solid debris out of the septic tank and into the leach field reduces the future life of that expensive component of a septic system.
Also see TUBE for MEASURING SCUM & SLUDGE for a tool that can make both scum and sludge thickness measurements with a single device.
For deep or hard to access or commercial septic tanks that may need close monitoring, see ELECTRIC MONITOR for SCUM & SLUDGE and also take a look at Other Measures Scum / Sludge. Septic tank pumping pumping frequency guidance is provided in a table at our website (seelinks listed at Related Topics .)
At SEWAGE LEVELS in SEPTIC TANKS we explain how to interpret the meaning of high or low sewage levels in the septic tank as well as thick or thin scum or sludge levels.
Continue reading at : HOW TO MEASURE SEPTIC SLUDGE LAYER
Below at in the form of individual detailed articles are the Steps in Septic Tank Cleaning Procedure in the order that they should be performed
Green link shows where you are in this article series.
Frequently Asked Questions (FAQs)
No FAQs have been posted for this page. Try the search box below or CONTACT US by email if you cannot find the answer you need at InspectApedia.
Use the "Click to Show or Hide FAQs" link just above to see recently-posted questions, comments, replies, try the search box just below, or if you prefer, post a question or comment in the Comments box below and we will respond promptly.
Search the InspectApedia website
HTML Comment Box is loading comments...
Technical Reviewers & References
Related Topics, found near the top of this page suggest articles closely related to this one.