Septic drop box or D-box leaks & flooding:

This article explains the causes & suggests cures for effluent leaks, odors, or smells at the septic distribution 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.

Distribution Box Clogs, Flooding, Leaks & Odors: troubleshooting & repair

Water leaking either into or out of a septic system D-box is a sign of trouble that needs investigation and repair, but the cause, implications, and cure of these two conditions are different.

We'll discuss these two different problems, followed by repair suggestions for various D-box leak problems.

Water leaking Out of the Distribution box.

1. The soils around the septic field may be saturated with groundwater,
   
   flooding the drainfield and backing up and out through the D-box cover.
   
   Just sealing the cover wouldn't fix anything in this case.
   
   You'd need to divert groundwater away from the drainfield itself.
2. The septic drainfield or leaching beds may be saturated from having become clogged
   
   and may well be at end of lits life.
   
   If this is the case the backup of effluent is occurring because the soil is no longer absorbing effluent.
   
   You'll need to investigate to decide if the problem is a blocked or damaged or clogged drainfield line or if the whole field needs replacement.

Water Leaking Into the Distribution Box

You don't want surface or ground water leaking into the D-box since in any quantity that water will flood the drainfield, damaging it, risking a costly failure or sewage backup.

If the D-box cover fits pretty flush and smooth atop the distribution box, the amount of water that leaks in through the top should be trivial.

If the top is quite uneven and leaky, and if you can't correct surface drainage to keep water away from the distribution box you might need to add a compressible rubber or foam gasket between the D-box lid and the edges of the distribution box itself to reduce leaks there.

Watch out: Don't cement the distribution box lid in place or you won't be able to open it for inspection, adjustment, or repair.

Diagnose & Stop Leaks & Odors at the D-box

If you see leaks or smell odors at the septic effluent distribution box or "D-box" we do not recommend that you simply try sealing the D-box lid.

First excavate or remove enough soil to allow you to open the D-box cover and inspect the interior for flooding.

If there is standing water in the D-box then the problem is one of the failures discussed earlier on this page: a failing septic drainfield that is flooded or area surface runoff leaking into and flooding both the D-box and the septic fields.

But if you see signs of D-box flooding, such as flood lines on the interior sides of the D-box wall, but the effluent level subsides so that the box does not remain flooded, then we suspect that the D-box is too small AND that with the small size, the effluent (it's not graywater) is not being accepted into the drainfield rapidly-enough.

Normal vs Abnormal Water (Effluent) Levels in the Septic D-box

Septic effluent liquid ("water") in the very bottom of the D-box, as shown in the photo above, is normal and harmless provided it is never above the lowest D-box outlet opening.

If there is Wastewater in the d-box above the bottom of the outlet pipes to the drain field, or above the flow balancing openings in those pipes (photo below), then I suspect the drainfield pipes are either blocked or flooded.

D-box Flooding with Septic Effluent Pump Systems

If your septic system uses an effluent pump to move septic effluent from the septic tank to the septic drainfield through a drainfield distribution box, then it is possible that the result is the pump is filling the D-box faster than its outflow rate, causing backup and odor complaints.

A much larger D-box, sufficient to receive and then drain by gravity into the drainfields the whole pump cycle volume would be one approach that may tempt you but I don't recommend it.

Rather, you need to look at the inflow capacity of the drainfield - it may be that the drainfield is under-sized, or worse, that it is poorly designed / installed and is flooding, or possibly the line balancing openings in the D-box that balance flow into different drainfield lines are too small.

In sum, if you watch the D-box when the effluent pump cycles you'll probably see that around 125 gallons of effluent are surging into the D-box and overflowing it because the in-flow rate is faster than the outflow rate.

If the D-box overflows only at the very end of the pump cycle you could see if your pumping system rate can be adjusted to send effluent to the D-box more slowly.

D-box Flooding with Gravity Septic Effluent Distribution Systems

If you see flooding in the D-box when your septic system does not make use of an effluent pump or dosing system to move effluent from septic tank to drainfield, then more likely the problem is a blocked effluent line (one or more) between D-box and drainfield, or a sluggish, failing drainfield.

 

Clogged / Flooding / Smelly D-box Repair Procedures

Diagnose the D-Box Flooding Before Starting Septic System "Repairs"

Some septic system backups, failures, or flooding in the D-box can be traced to broken, blocked, or root-clogged septic effluent lines.

In addition to inspecting the distribution box itself, before digging up the system or beginning an expensive septic drainfield repair/replacement project, ask your septic contractor or plumber to inspect the entire effluent line system for breaks, blockages, or root invasion.

If the D-box itself 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.

If there is just just one effluent pipe in and one pipe out of this D-box, this is probably an access or inspection port and a connection between pipes, not much more.

If, as is usual, 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.

Inspect the remaining effluent piping between that point and the septic drainfield to locate an actual distribution box that splits the effluent out into multiple septic drainfield sections or pipelines.

Seal D-Box Covers Against Both Odors & Groundwater

If at inspection you find a damaged seal on the D-box lid, the choices are to replace the whole unit (this is not a costly part) but often you can use a simple foam gasket to seal the lid to the box.

We're reluctant to use silicone sealants between D-box lid and box sides because that will make it very difficult to open, inspect, clean, or adjust the D-box distribution system in the future.

If there are roots in the D-Box 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 where effluent lines enter or exit the box.

Sealing the D-box lid is discussed in detail

at SEPTIC D-BOX COVERS

Replace Broken or Cracked D-Box or Splitter-Box Cover

A cracked cover over any buried tank or equipment, including not just the septic D-box but the tank itself, is dangerous as there is risk of someone falling into the opening.

Even without that risk of injury, we don't want surface runoff or groundwater leaking into the D-box because that becomes a source of septic drainfield flooding, septic tank back-flooding, and in the worst case, a sewage backup into the building.

So replace a damaged D-box cover and seal it to the box.

Repair Broken Effluent Pipes at the D-Box - Orangeburg Pipe Repair

At older septic systems that used Orangeburg pipe, and where you find broken pipe or a poor seal at the distribution box, you could replace a broken Orangeburg section with PVC pipe.

Because Orangeburg pipe and PVC pipe of the same approximate inner diameter have very different exterior diameters, you'll use a makeshift connection with a cement mix or, as I prefer, a rubber flexible Fernco coupling [Website] (shown above) to connect the PVC to the remaining Orangeburg pipe.

Watch out: when you find broken Orangeburg pipe at a septic system, what I'm concerned about is what I call the old house spaghetti problem. Once the spaghetti has sat in the colander and got cold it's all stuck together when you can't pull one strand out. Starting to work on any old material can be similar.

Probably at such a septic system there is more Orangeburg damage than you thought.

Ask a plumber who has a sewer line camera inspect the entire line before starting repairs and to avoid the spaghetti problem.

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Continue reading  at SEPTIC D-BOX COVERS or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see these

Recommended Articles

• FLOODED SEPTIC SYSTEMS, REPAIR
• SEPTIC D-BOX INSTALL, LOCATE, REPAIR - home for septic distribution box, drop box, D-box
  • SEPTIC D-BOX COVERS - cover leaks, cover sealing, cover safety at the septic system distribution box
  • SEPTIC D-BOX FLOODING - causes & cures for flooding & leaks at the septic system distribution box or Drop Box
  • SEPTIC D-BOX INSPECTION - How to inspect the septic system distribution box for clues of septic drainfield condition
  • SEPTIC D-BOX LOCATION - how to find the D-box
  • SEPTIC D-BOX PIPING - solid vs. perforated piping
  • SEPTIC D-BOX SPECIFICATIONS - sanitary code examples of D-box requirements
  • SEPTIC D-BOX SPLITTERS - Using a D-box control or a Splitter Valve for drainfield resting & restoration
  • SEPTIC D-BOX TEMPORARY REPAIR - temporary repair bypassing the Drop Box may work in a few cases
  • 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 Odor
• SEPTIC DESIGN for FLOOD DAMAGE RESISTANCE
• SEPTIC TANK BACK FLOODING

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INDEX to RELATED ARTICLES: ARTICLE INDEX to SEPTIC DRAINFIELDS & D-BOXES

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