Septic System D-Box
Install, Inspect, Test & Fix Septic System Distribution Box
SEPTIC D-BOX INSTALL REPAIR - CONTENTS: Septic system distribution boxes - drop boxes: How to find the septic drainfield D-box - septic distribution box, D-box installation, specifications, design, leveling, adjustment, troubleshooting & repair. Simple repairs at the D-Box can improve septic drainfield performance and may eliminate septic odors. Using a D-box control or a Splitter Valve for drainfield resting & restoration
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Septic system D box installation, specifications, inspection, diagnosis, and repair:\
In this article series about septic system drop boxes we describe the best procedures for locating and inspecting, repairing or replacing the septic drainfield distribution box, or the "D-box" or "Splitter box".
If the D-box is leaking, smells, or is tipped, clogged, or otherwise not working this article describes how to diagnose & fix the trouble.
This series of septic system installation, maintenance & repair articles discusses the Inspection and Reporting the Condition of Private Residential Waste Disposal Systems - or - Where Does it Go When I Flush? and ... Will We Meet Again?
Septic System Effluent Distribution Boxes: the D-Box
Definition of a Septic D-Box: a septic distribution box is a container used to receive septic system effluent from a septic tank and to re-distribute the effluent into a network of attached drain-field or soakaway bed absorption trenches & pipes.
The D-box works by gravity, flowing effluent into the drainfield (or leachfield) piping network.
SEPTIC D-BOX TROUBLESHOOTING - simple repairs at the D-Box can improve septic drainfield performance and may eliminate a Tipped D-box, Distribution -Box Leaks, Drop Box Odors
How to Find the Septic System D-Box
Question: distance from the septic tank to the D-box?
How far away from the septic tank is the dbox? - Kristin Clary
How far from the main tank is the D box located on average? - Fishass
[Click to enlarge any image]
Reply: Distance from the Septic tank to the D-Box:
Kristin & Fishass: there is not a fixed distance from the septic tank to the distribution box; rather, its location depends on the space for and layout of the septic drainfield. But you can often get a fair idea where the D-box is likely to be by any of several means:
- running a snake or probe from the septic tank outlet until it stops will give the distance to the D-box (probably)
- look for a depression in the ground a couple of feet in diameter and between the septic tank and the drainfield.
- Look at the site layout for where the D-box could possibly be located. For example, if the drainfield site is level and rectangular, the D-box would typically be at or near the edge of the drainfield closest to the septic tank.
See SEPTIC DRAWINGS for some sketches that give an idea where the distribution box is typically found
D-BOX Specifications & Code Requirements
The following building code example specification for septic system distribution boxes is excerpted from SEPTIC DISTRIBUTION LINES, BOXES, TYPES, NYS-A.7 Effective Date: 12/01/90
Title: Appendix 75-A.7 - Distribution devices
(1) Distribution Box Design Specifications - the D-Box Specs
(i) For accessibility, it is necessary that the distribution box be
located and have a removable cover not more than 12 inches below grade.
Where, due to site conditions, a distribution box must be greater than
12 inches below the surface, an extension collar shall be installed to
within 12 inches of the surface.
(ii) All outlets from the distribution box shall be at the same level to
insure the even distribution of flow.
(iii) To minimize frost action and reduce the possibility of movement
once installed, distribution boxes must be set on a bed of sand or pea
gravel at least 12 inches thick.
(iv) The drop between inlet and outlet inverts shall be at least two
inches. A baffle is required at the inlet side of the box when the
slope from the septic tank to the box exceeds 1/2 inch per foot or when
siphon dosing is used.
(v) There shall be a minimum two inch clearance between the inverts of
the outlets and the bottom of the box to prevent short-circuiting and
reduce solids carry-over.
(vi) Distribution boxes may be constructed in place or purchased
prefabricated. When concrete is used to construct boxes, it shall have
a minimum compressive strength of 2,500 psi at 28 day set.
(vii) Prefabricated boxes may be constructed of concrete, fiberglass, or
plastic. The boxes shall be installed in conformance with the
manufacturer's instructions in addition to the requirements above.
INSPECTING THE D-BOX - Inspecting the Septic System Distribution Box
The distribution box (more than one may be in use) connects a single effluent line from the septic tank to a network of absorption system components such as drainfield leach lines or to a network of seepage pits or galleys.
Question: Repairman says hard water will ruin my water treatment system and drainfield
I have hard water and treat it with a culligan system. My neighbor had a title five and needed to have his D-box replaced to pass. The repairman said the whole street will have the same problem because of hard water will my treated water system help or hurt my system - Kevin 9/29/12
How do they test for Title 5?
Water softeners, installed to improve water that is too high in mineral content, do not specifically attack D-boxes, but an improperly adjusted softener can increase salt dose into a drainfield, impacting its function and life, and a softener stuck in backwash mode can flood the field.
And it doesn't quite make sense to me for your repairman to say that hard water will damage your water softener. The purpose of the water softener is to treat hard water. That's its job.
Search InspectApedia for
Water Softener Impact on Septic Systems
to read the details.
If you search InspectAPedia for
Massachusetts Septic System Testing Law
you'll find a discussion of the law, specifications, and test procedures. It's more than a "test" - involving site inspection, history, water table depth, etc
Question: how often should the soakaway bed / septic field distribution box be checked?
(July 15, 2014) Anonymous said:
at what age should the distribution box be inspected.
Good question, Anon, for which I've not found an authoritative answer for these reasons:
OPINION: The need for & frequency of inspection of the D-box would vary by septic system design, local soil properties, level of usage. For example in a system design that uses manually-set alternating soakaway bed field trenches the frequency would be at least that of the planned swap between fields - perhaps every 5 years.
Most people ignore the D-box and never look there until there is a sign of trouble. Then the box is located, opened and inspected for evidence of the septic field condition. That's when defects such as tipping, leaks, or uneven outlet distribution are more likely to be discovered.
If I were to propose a D-box inspection frequency I'd suggest
1. Inspect any time there is other evidence of a septic system backup, failure, or effluent breakout
2. Inspect the D-box on a frequency specified by the septic system designer - if any was specified. For example alternating bed septic systems that use a pump or siphon system may specify annual inspection to check for equipment malfunction or for adjustment.
3. Inspect at the frequency of required drainfield area exchange / rest / modification
4. Inspect at 5-10 year frequency in other conditions
Question: sewage does not flow uphill
(Aug 25, 2014) Charlie said:
Hi, while digging a trench I accidentally broke the main septic line between my Septic Tank and D-Box. The pipe was schedule 20 4" septic and was oblong. The pipe between the break and the D-Box was full of sludge. Also found out lid on D-Box was broken so it was plugged solid with dirt. I suspect this happened about 3 months ago while I was rototilling.
Was able to clean everything out and fix the broken line, however discovered that the D-Box is actually uphill from septic tank. It also appeared that the pipe was possibly cracked even before I hit it. Their was a lot of black soil underneath the break. My guess is it happened 10 years ago when the original irrigation system was put in.
I know the tank is not full, so my question is what caused all the sludge build up in the pipe? Was it cracked pipe, the uphill grade, or the plugged D-Box?
Oh for pete's sake: who the heck put the D-box uphill from the septic tank? The proverbial expression is "S_it doesn't flow uphill"
That would leave sludge in the pipe.
Question: flooding seen at the D-box
(Jan 6, 2015) Jamie Steele said:
Ok, i had a back up into my house. I had a company come out and pump the septic tank out (which was full of solids). They mentioned that they thought the distribution box might be clogged as well.
So a couple of days later we dug up the d-box. When we got to the lid on the dbox a hole accidentally was knocked into the lid and water started coming up from the dbox (the lid subsequently fell apart so a new had to be made). We pumped the dbox out but there were no solids in the dbox. We snaked the line from the septic tank to the dbox as well as both distribution lines and found no blockages of any kind.
Then 3 days of solid rain hit the area and we basically pumped on a regular basis to keep the hole from filling up with water.
Now we have the lid finished but not installed back on the dbox. Is it normal in this situation, with the lid not on the dbox, for water to keep coming up from the dbox. Or is it a sign of another issue?
What you describe is an illustration of why pumping a septic tank will not fix a septic backup problem. All it does is buy some time - until the tank is filled again, which could be hours or days. The backflow out of the D-box shows that the drainfield is saturated = flooded - not working.
Question: solids in the D-box or septic distribution box
20 January 2015 Gillian Andrew said:
I have a gravity operated septic system under 6 years old. I had the tank pumped a few weeks ago because I'd noticed water making the driveway stay wet much longer on one side after heavy rain, nearest the septic field, and starting about halfway down it, about run 2 or 3 of 4. The tank was full. But the problem is still present, so I uncovered the Distribution box to inspect it for the first time. It has flow levellers. There is opaque dark brown liquid up to or close to the hole in each leveller. It looks scummy. There is no smell. Is there a problem?
In normal conditions a septic tank is always "full" - to the bottom of its outlet pipe. Pumping won't fix a thing though it may give a few days of relief.
If the drainfields are flooded the system needs replacement or repair or surface water or runoff diversion away from the soakaway beds.
If the D-box is full above its outlet levelers that's another clue that the fields are saturated.
If the D-box contains solids that's more disturbing news as it suggests that the septic tank outlet baffle is damaged or lost. Pushing solids into the soakbed significantly shortens its further life.
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 Thanks to reader Nicholas Day for discussing D-box troubles and repairs, September 2010
 Zoeller Pump Company, 3649 Cane Run Rd., Louisville, KY 40211, Phone: 1-800-928-7867, 502-778-2731
Fax: 502-774-3624. Technical support and/or quote related emails: firstname.lastname@example.org. Zoeller produces just about every kind of septic, sewage, effluent, grinder, and sump pump. Homeowners who need a sewage pump are asked to contact their local representative or retail sales outlet. Zoeller classes their pumps into these categories:
Grinder pumps, such as Zoeller's 810/815 Turnkey Grinder Systems, 800-series Grinder Pumps, Cold-Climate grinder pumps, Simplex prepackaged grinder pump systems, and Simplex and Duplex (two pumps) grinder systems including four outdoor use.
Utility, pedestal, & gas engine pumps. These are portable gas-engine powered pumps used typically in construction, service, or emergencies
Sewage & Dewatering pumps, such as certain Aqua-Mate Models and Waste-Mate models, and Sewage-Waste 600-series pumps
Splitter for septic effluent distribution. Web search 5/1/12, original source
https://app.qleapahead.com/rtp/LibraryGet.aspx?asset=85356,63 [copy on file as septic/D-boxes/Zoeller_D-BOx_Splittert.pdf ] Website: www.zoeller.com
Sump, Effluent, Dewatering pumps, such as Water Ridd'r , Mighty-Mate, Aqua-Mate, Flow-Mate, and High Head Flow-Mate pumps - of certain models - be sure to read the manufacturer's intended use for a pump model before purchasing it
 "Drainfield Rehabilitation", Pipeline, Winter 2005, Vol. 16, No. 1, NESC, National Environmental Services Center, 800-624-8301 [copy on file as [/septic/D-boxes/NESC_2005-16_1.pdf
 Advanced Onsite Wastewater Systems Technologies, Anish R. Jantrania, Mark A. Gross. Anish Jantrania, Ph.D., P.E., M.B.A., is a Consulting Engineer, in Mechanicsville VA, 804-550-0389 (2006). Outstanding technical reference especially on alternative septic system design alternatives. Written for designers and engineers, this book is not at all easy going for homeowners but is a text I recommend for professionals--DF.
 Builder's Guide to Wells and Septic Systems, Woodson, R. Dodge: $ 24.95; MCGRAW HILL B; TP;
Quoting from Amazon's description: For the homebuilder, one mistake in estimating or installing wells and septic systems can cost thousands of dollars. This comprehensive guide filled with case studies can prevent that. Master plumber R. Dodge Woodson packs this reader-friendly guide with guidance and information, including details on new techniques and materials that can economize and expedite jobs and advice on how to avoid mistakes in both estimating and construction. Chapters cover virtually every aspect of wells and septic systems, including on-site evaluations; site limitations; bidding; soil studies, septic designs, and code-related issues; drilled and dug wells, gravel and pipe, chamber-type, and gravity septic systems; pump stations; common problems with well installation; and remedies for poor septic situations. Woodson also discusses ways to increase profits by avoiding cost overruns.
 Country Plumbing: Living with a Septic System, Hartigan, Gerry: $ 9.95; ALAN C HOOD & TP;
Quoting an Amazon reviewer's comment, with which we agree--DF:This book is informative as far as it goes and might be most useful for someone with an older system. But it was written in the early 1980s. A lot has changed since then. In particular, the book doesn't cover any of the newer systems that are used more and more nowadays in some parts of the country -- sand mounds, aeration systems, lagoons, etc.
 Onsite Wastewater Disposal, R. J. Perkins;
Quoting from Amazon: This practical book, co-published with the National Environmental Health Association,
describes the step-by-step procedures needed to avoid common pitfalls in septic system technology.
Valuable in matching the septic system to the site-specific conditions, this useful book will help you install a reliable system in
both suitable and difficult environments. Septic tank installers, planners, state and local regulators, civil and sanitary engineers,
consulting engineers, architects, homeowners, academics, and land developers will find this publication valuable.
 Onsite Wastewater Treatment Systems, Bennette D. Burks, Mary Margaret Minnis, Hogarth House 1994 - one of the best septic system books around, suffering a bit from small fonts and a weak index. (DF volunteers to serve as indexer if Burks/Minnis re-publish this very useful volume.)While it contains some material more technical than needed by homeowners, Burks/Minnis book on onsite wastewater treatment systems a very useful reference
for both property owners and septic system designers. We refer to it often.
While Minnis says the best place to buy this book is at Amazon (our link at left), you can also see this book at Minnis' website at http://web page .pace.edu/MMinnisbook
 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, 8271 1302, 7100 Engineering, 2300 Recreation, September 1982, web search 08/28/2010, original source: http://www.fs.fed.us/t-d/pubs/pdfimage/82711302.pdf
 Septic System Owner's Manual, Lloyd Kahn, Blair Allen, Julie Jones, Shelter Publications, 2000 $14.95 U.S. - easy to understand, well illustrated, one of the best practical references around on septic design basics including some advanced systems; a little short on safety and maintenance. Both new and used (low priced copies are available, and we think the authors are working on an updated edition--DF.
Quoting from one of several Amazon reviews: The basics of septic systems, from underground systems and failures to what the owner can do to promote and maintain a healthy system, is revealed in an excellent guide essential for any who reside on a septic system. Rural residents receive a primer on not only the basics; but how to conduct period inspections and what to do when things go wrong. History also figures into the fine coverage.
 Grass is Always Greener Over the Septic Tank, Bombeck, Erma: $ 5.99; FAWCETT; MM;
This septic system classic whose title helps avoid intimidating readers new to septic systems, is available new or used at very low prices.
It's more entertainment than a serious "how to" book on septic systems design, maintenance, or repair. Not recommended -- DF.
 US EPA Onsite Wastewater Treatment Systems Manual Top Reference: US EPA's Design Manual for Onsite Wastewater Treatment and Disposal, 1980, available from the US EPA, the US GPO Superintendent of Documents (Pueblo CO), and from the National Small Flows Clearinghouse. Original source http://www.epa.gov/ORD/NRMRL/Pubs/625R00008/625R00008.htm
 Water Wells and Septic Systems Handbook, R. Dodge Woodson. This book is in the upper price range, but is worth the cost for serious septic installers and designers.
Quoting Amazon: Each year, thousands upon thousands of Americans install water wells and septic systems on their properties. But with a maze of codes governing their use along with a host of design requirements that ensure their functionality where can someone turn for comprehensive, one-stop guidance? Enter the Water Wells and Septic Systems Handbook from McGraw-Hill.
Written in language any property owner can understand yet detailed enough for professionals and technical students this easy-to-use volume delivers the latest techniques and code requirements for designing, building, rehabilitating, and maintaining private water wells and septic systems. Bolstered by a wealth of informative charts, tables, and illustrations, this book delivers:
* Current construction, maintenance, and repair methods
* New International Private Sewage Disposal Code
* Up-to-date standards from the American Water Works Association
 Wells and Septic Systems, Alth, Max and Charlet, Rev. by S. Blackwell Duncan, $ 18.95; Tab Books 1992. We have found this text very useful for conventional well and septic systems design and maintenance --DF.
Quoting an Amazon description:Here's all the information you need to build a well or septic system yourself - and save a lot of time, money, and frustration. S. Blackwell Duncan has thoroughly revised and updated this second edition of Wells and Septic Systems to conform to current codes and requirements. He also has expanded this national bestseller to include new material on well and septic installation, water storage and distribution, water treatment, ecological considerations, and septic systems for problem building sites.
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