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SEPTIC SYSTEM INSPECT DIAGNOSE REPAIR
SEPTIC CARE INSTRUCTIONS
SEPTIC D-BOX INSPECTION
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 & SEPTIC CONTAMINANTS
SEWAGE BACKUP, WHAT TO DO
SEWAGE BACKUP TEST & CLEANUP
SEWAGE BACKUP PREVENTION
SEWAGE CONTAMINATION in buildings
SEWAGE CONTAMINANTS in FRUIT / VEGETABLES
SEWAGE EJECTOR / GRINDER PUMPS
SEWAGE LEVELS in SEPTIC TANKS
SEWAGE NITROGEN CONTAMINANTS
SEWAGE PATHOGENS in SEPTIC SLUDGE
SEWER BACKUP PREVENTION
SEWER GAS ODORS
SEWER LINE REPLACEMENT
SINKHOLES, WARNING SIGNS
SMELL PATCH TEST to Track Down Odors
SOAKAWAY BED FAILURE DIAGNOSIS
SULPHUR & SEWER GAS SMELL SOURCES
TOILETS, INSPECT, INSTALL, REPAIR
TOILETS, DON'T FLUSH LIST
TRAPS on PLUMBING FIXTURES
TREATMENTS & CHEMICALS, SEPTIC
VIDEO GUIDES: Septic Videos
WASHING MACHINES & SEPTIC SYSTEMS
WATER SOFTENERS & CONDITIONERS
WATER SUPPLY & DRAIN PIPING
WASTEWATER TREATMENT BASICS
WATER, WELLS, WATER TANKS: TESTING GUIDE
WINTERIZE A BUILDING
Septic system D box inspection, diagnosis, and repair: here we describe the best procedures for locating and inspecting, repairing or replacing the septic drainfield distribution box, or the "D-box" or "Splitter box". This series of articles discusses Inspection and Reporting the Condition of Private Residential Waste Disposal Systems - or - Where Does it Go When I Flush? and ... Will We Meet Again?
Green links show where you are. © Copyright 2013 InspectAPedia.com, All Rights Reserved. Author Daniel Friedman.
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.
The photo (left) shows the adjustable weir outlets that permit balancing flow among drainfield lines. (Source EPA who used photo from Ayres Associates.) More sketches of D-box layouts and configurations are shown in this EPA drawing.
Regulating effluent distribution: In good system design the outlet openings from the distribution box to each drainfield line can be adjusted to regulate the flow among the various absorption lines.
Elegantly simple, a plug with an eccentric hole is inserted into the end of each leach line fed from the D-box. By turning the plug in the end of the leach line pipe one can place the eccentric hole higher or lower with respect to the bottom of the distribution box, thus compensating for a slightly tipped box, differences in leach line length, or differences in leach line condition.
Uneven effluent distribution: If a distribution box becomes tipped (or clogged) effluent may be routed to only a portion of the absorption system, thus overloading it and leading to a "breakout" of effluent at the surface or to clogging and system backup.
An examination of the septic system distribution box interior may show flood lines in the box if the drain field has been clogged or saturated in the past even if at the time of inspection the box is not flooded.
If the septic drainfields have been flooded you should be pessimistic about the remaining life of the absorption system.
If the septic drainfield distribution box is tipped and/or septic system effluent arriving from the septic tank has not been uniformly distributed among the drainfield lines (assuming they are of equal length and in equally good soils), only a simple adjustment of the outflow may be needed.
Round plugs with eccentric openings may be present or can be inserted in the D-box outlet openings to regulate flow among the individual absorption lines. (C)Trap Daniel Friedman Copyright Protected text. Also see ALTERNATING BED SEPTIC SYSTEMS.
Tipped or flooded distribution boxes, resulting in uneven loading of soil absorption system lines. This condition can flood one or two lines leading to early field failure.
Question: Tipped septic effluent distribution box, standing water at end of one leach line
With thanks to clarifications from reader Doug (March 2013), we recap the effluent distribution piping connections to this D-box as follows:
Without the elbow, effluent flows more forcibly across the box and into the opposing outlet, but very little effluent will make the 90-degree turn into the perpendicular outlet. This is a very common installation practice
If you knew for example that one of your lines was much longer than the other, you'd send more effluent to the longer line - presuming they are both working ok.
As you report that one of the laterals showed a sign of failure during wet weather several years ago, you might want to try to re-balance the effluent flow sending more (or perhaps temporarily, most) of the effluent into the other drainfield line. But to have an accurate idea of the condition of the drainfield sections or leach lines before adjusting the effluent flow in your D-Box, the best step would be to carefully excavate near the end of each of the two leach lines (presuming you don't already have inspection ports installed). Look at the condition of the soils there, particularly, look for standing water or effluent.
Because the D-box is a small thing and not deep, it shouldn't be a big job nor too costly to dig it out, install a larger one, make sure the D-box is not tipped, and that effluent is flowing as desired into both of the drainfield lines.
But you should also check the septic tank condition, especially the outlet baffle, and the scum/sludge levels, to be sure the tank is pumped on schedule (SEPTIC TANK PUMPING SCHEDULE) and that the baffles are in place and working. (SEPTIC TANK BAFFLES).
Another problem that could send sludge into the D-box would be a septic tank that floods from groundwater leaking into it, so you will want to check that too. At also see SEPTIC TANK INSPECTION PROCEDURE, and SEPTIC TANK INSPECTION PROCEDURE, and finally, see Septic Tank Leaks.
Frequently Asked Questions (FAQs) about septic system distribution box (D-box) troubleshooting
Question: water is leaking out of my distribution box. Should the lid be sealed?
I have septic water leaking out of my distribution box. I the lid suppose to be sealed or does it just sit on top?? My system is is pumped up hill to a ditribution box - Robert
Reply: water leaking into or out of a D-box is a sign of trouble that needs investigation and repair;
Water leaking out of the distribution box
If you see "water" leaking out of the septic drainfield D-box it's a sign of trouble. I suspect one of two typical causes.
Water leaking into the distribution box
Septic Effluent Flow Rate Capacity - Zoeller's Tru-Flo Splitter [D-box]
|Number of outlet openings (drainfield segments fed)||Maximum effluent inflow rate handled by the Splitter|
|5 openings||30 gpm|
|4 openings||21 gpm|
|3 openings||17 gpm|
|2 openings||13 gpm|
See our contact information for Zoeller at the reviewers section at the end of this article for a link to the Zoeller D-Box-Splitter for septic effluent distribution system information.
Watch out: Zoeller warns that if you use this device, which does a more careful job of routing effluent among the different drainfield branches, it is clog-prone if you don't include a septic filter in the system at the effluent outlet end. Indeed, an effluent filter will protect and extend the life of any drainfield and its components.
I have a system with a pump station that pumps gray water uphill about 50 yards. Today I noticed water percolating out of the ground near my drain field. I started digging and found what I assume is the d box. It was packed full of roots and the plastic seal around the pipe coming from the pump had been pushed out by the roots. I removed the roots but I could not remove the seal from the box. It has 5 more holes in it which 4 are closed and the other has a pipe leading to another concrete box 4-5 feet further out. The second box is much deeper than the first. It appears that the pipes T out after the first box. More digging tomorrow. I ran the pump after replacing the lid and packing dirt around the pipe but it just came out of the box instead of going through the system. The downstream pipe is open.
Can the seal be replaced around the incoming pipe or should the box be replaced?
Do the other "boxes" typically have a lid like the first one does? I was wondering if I should dig them up and check for clogs.
The system is 9 years old and is pumped every year.
Thanks for any info and for this great website.
Kenneth M. 1/8/2012
Sure, if the D-box has become clogged by roots, and probably tipped and askew too, it needs to be cleaned, leveled, and the surrounding roots cut back to slow their re-invasion. Because you have just one pipe in and one pipe out of this D-box, and because you found a second deeper distribution box on your septic system, I suspect the first one is an access or inspection port and a connection between pipes, not much more. Ultimately, presuming there is more than one leach line at your drainfield, there will be a D-box that distributes effluent among multiple lines - you'll want to find and check the condition of that device. The T-pipes you describe make it sound as if the septic installer forgot what the D-box was for but just stuck one in anyway. Too bad.
About the damaged seal on the first D-box, the choices are to replace the whole unit (this is not a costly part) or you could try cutting away the offending roots and digging around the pipe that enters or leaves the D-box, pouring concrete around the pipe at the outside of the D-box to try to get a decent seal.
I have 8 lines coming off my d box. my yard is slightly pitch to one side. that side also sees most of the rain water. The surface never seems to fully dry like my other lines. speed levelers were installed when the dbox was replaced. should those 2 lines be capped and shut off for a while to regain a better saturation point? i you, JB 5/10/12
I agree with your idea to cap off saturated drainfield lines. Drainfield trenches tend to wear out (clog the soil) beginning at the trench end most distant from the D-box, slowly working the clogging back towards the D-box. Giving the drainfield a rest for 5 years or more might help those sections recover provided that they are not being soaked from some other water source.
Keep in mind that effluent breakout at ground surface is not only a failure indicator, it is unsanitary. In sum, if the area is wet, the effluent distribution lines in that area are not treating efflent anyway, just contaminating the environment.
Finally, if the wet area were in say the last 5 feet of a 60-foot line, you might try excavating and capping off the wet ends to see if that gives you longer use of the rest of the leaach line.
My D box is level, it flows nicely and is made of concrete. Unfortunately the lid has failed and the sides are starting to crumble. Do I have to replace the whole box or could I simply form and pour concrete around the old one? Would this be an acceptable repair method? - Scott 5/1/12
Scott, if you can repair the dbox to be water tight in place that's fine, but I worry its a wasted effort ad if it's crumbling the original concrete mix may have been bad - if so the box will continue to crumble - replacement may be in order and not too costly. Certainly you don't want to pour a new "lid" in place that seals the D-box making it impossible to open, inspect, adjust, in the future.
our cleanout access covers get about an inch of water on it when we run the washer and shower in the house. The water comes up quickly on just the cover and then two minutes later it's gone. We have the tank cleaned once to twice a year; we call the company that cleaned it and the are telling us they need to dig up the D box. I have chedk the yard and there is standing water anywhere. Does diging up the D box sound correct. Or sholuld they just check for a clog? - John 6/26/12
John if the septic tank or dbox is flooding as you describe it sounds as if the fields are clogged or flooded. Your system is in trouble, needs diagnosis and repair for sure. Because it's easy and quick it's a great quick-check to look into the D-box to see what's going on.
Open the D-box covers, flush a few toilets in the home, or run the washer, and watch in the D-box. If you see efflent entering and flooding the box then we figure the outlet lines and drainfield are either blocked or saturated.
Start a more throughou inspection at the septic tank, include piping to the D-box, the D-box, and the fields. For example if the tank inspection shows us that the tank baffles are gone, we know we've been pushing solids into and ruining the fields.
xI 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.
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