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Septic distribution box inspection - US EPA Septic System D-Box Splitters for Drainfield Rest & Recovery
Use Splitters / Diverter Valves at the Septic System Distribution Box

Septic drop box splitters:

Use of special control valves in the septic system D-box or distribution box can give sections of the septic soak bed or leachfield or drainfield a rest, allowing for drainfield recovery.

This article describes septic d-box splitters or flow diverters or flow control valves & their use and gives product sources - where to buy a D-box splitter for drainfield R&R.

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".

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- Daniel Friedman, Publisher/Editor/Author - See WHO ARE WE?

Septic System D-Box Splitters - Drainfield Resting

Reader Question: What's the difference between a septic system D-box and a Splitter?

What is the difference in splitter box and a D box? - T.C.

Reply: why we might need a Zoeller Tru-Flow Splitter in place of a conventional Septic D-box - alternating drainfields & effluent flow balancing

Basically there is no difference in function between a D-box and a Splitter box. All D-boxes have some capability of adjusting the flow of effluent among different D-box outlets - a technique that can extend drainfield life by giving some drainfield sections a rest for two years or so between services.

In some literature the control that permits diverting effluent among drainfield segments, or shutting it off entirely, is called a splitter valve.[4] In other installations, a simple manual plug or cap is inserted or adjusted at each outlet opening inside the distribution box.

Some "splitter" boxes such as Zoeller's are more sophisticated than the simple concrete or plastic Distribution Boxes illustrated in the article above.[3]

Zoeller Pump Co who make septic system grinder pumps and other onsite wastewater piping and pump components, also produce and sell component that most of us call a "distribution box" and that accomplishes that function - routing effluent among drainfield lines: the Zoeller Splitter System. What's the difference?

In a conventional concrete D-box, it's just that: a plastic or concrete or fiberglass "box" into which one pipe delivers septic effluent from the septic tank, and from which two or more pipes carry effluent to drainfield trenches, galleys, or other disposal systems.

The distribution box routes effluent among the various lines and if properly installed we hope effluent is distributed evenly

. Some D-boxes include a round cover with an eccentric hole that can be rotated up or down to balance the effluent load among different drainfield sections.

Higher velocity pumped septic effluent may require careful effluent distribution control in the D-box - the Splitter

Zoeller's Splitter uses a series of internal baffles to control the routing of effluent among drainfield lines.

One reason we might need the baffles and more precise control of effluent distribution through the D-box (or Splitter) is that Zoeller, who manufacture sewage grinder pumps and septic effluent pumps, (we pose) may have found that pumped septic effluent arrives in the Splitter (or D-box) at a higher velocity than effluent that drains into the box from a septic tank by gravity.

At high velocity, effluent entering a conventional D-box may not flow uniformly among the multiple box outlets - instead it would charge across the box and flow mostly into the effluent line directly across from the inlet pipe.

Zoeller's baffles appear intended to prevent that problem by diverting flow uniformly among the various Splitter box outlets.

Zoeller's Tru-Flow [D-box] Splitter system includes diverter adjustments that help you fine tune and balance the effluent flow among various drainfield sections. The system can handle varying septic flow rates depending on the number of openings in use in the "box" - that is, depending on the number of outlets and drainfield sections that are in use.

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

Notice: other septic diverters or flow control valves from other manufacturers will have different operating flow rates and properties.

See our contact information for Zoeller just below and also at 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.

Reader Question: one side of my fields never dries out, we installed speed levelers and a new D-box. Should we cap off the wet area lines?

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

Reply:

JB:

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 effluent 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 leach line.

Question: my septic D-box is flooded - is there a Diverter Valve for a second Seepage Pit?

Flooded D-box - leads to question about alternating seepage pits and diverter valves or flow valves (C) InspectApedia.com JP

2019/04/15 JP said

How can I diagnose if my issue is the D-box or seepage pits? Also can you tell if there is a diverter valve from these picture? I recall that my septic inspector (15 years ago) said something about selecting and alternating pits. I am not sure how to do this. Any recommendations?

This Q&A were posted originally at SEPTIC D-BOX INSTALL, LOCATE, REPAIR

[Click to enlarge any image]

Reply: (mod) - Cescription of Septic Flow Diverter Valves & Alternating Bed Septic Switch Frequency

Septic diverter valve - Bull Run discussed and cited at InspectApedia.comJP

If that flooded box in the left of the photo is your D-box and if it's top is off then it's flooded.

That tells us that the drainfield or seepage pit to which the D-box is sending effluent is either blocked or in total failure.

Illustration: this is a 3-way Bull Run diverter valve from American Manufacturing Co., cited below.

A diverter valve, also sometimes called a flow control valve, for septic systems is in essence a switch that will either

1. choose which of two (or more) destination drains, pipes, drainfields, or seepage pits to which to send wastewater

or in some designs

2. can adjust the balance to split the routing wastewater between two destinations simultaneously - i.e. niether of them is shut off.

If you have a septic design with alternating seepage pits then yeah you might have a diverter valve that swaps between them.

Often the diverter valve has a standpipe and a cap that's pulled off to permit using of a simple T-handled tool to turn the valve - that avoids having to dig it up.

You could look under the white cap on the standpipe in the upper right of your photo to see what's there - it could be
- an inspection port
- a vent
- access to a diverter valve

Let me know what you find.

The bad news is that once a seepage pit is flooded or stops accepting effluent it's basically shot. There are fellows who, for a fee, will jet the bottom (if it's open to soil) or try other magic bullets to "restore" a failed seepage pit (or drywell).

In my experience these rarely work or rarely give relief for more than a short time.

Watch out: jetting a home made or site built seepage pit or drywell can cause it to collapse - if someone falls in it's a quick and ugly death. We've reported on such fatalities here.

Read more at

SEEPAGE PITS

and at

SEPTIC & CESSPOOL SAFETY

The following excerpt is from "Operation and Maintenance of Your Sewage Treatment System" published by the Ohio health department.

Diverter Valve/Distribution Box

Diverter valve flow control standpipe and access at InspectApedia.comIf you have a diverter valve, the valve separates the leach field into two fields. The valve should be turned every three months to alternate the field and allow one field to rest while the other is absorbing the wastewater. If you have a distribution box, the wastewater is distributed to each leach line equally.

Each pipe in the box has a turn dial cap with a hole in the cap to allow water to flow into the leach line. Half of the caps should be turned with the holes up stop water flow and half should be turned with the holes down to allow for flow.

Every three months every cap should be turned 180 degrees to either allow flow or stop the flow. This will allow each line to rest while the others are absorbing wastewater. - Athens OH DOH retrieved 2019/04/15 original souirce: http://www.health.athens.oh.us/environmental/om_sewage.html 2019/04/15

Really? In our OPINION "every three months" is questionable advice for most septic fields in most soils, designs, and uses.

Why? Because once a biomat has begun to clog the soil around a drainfield trench or septic seepage pit wall it can take a year or even several years of total rest for the soil bacteria to break down the biomat layer enough to restore the field and soil percolation rate.

Frequent diverter valve switching might allow wet soils to "dry out" but that's not getting rid of the biomat. And if your septic fields or seepage pit are failing because they're flooded, just drying out is not likely to give more than temporary relief.

The underlying problem - flooding from groundwater - needs to be fixed OR if the flooding is because of soil clogging, the field or pit needs replacement - or a mutli-year rest.

The sketch below illustrating how a diverter valve might be used to manage two alternating drainfields is excerpted from instructions from American Manufacturing Co. who produce the Bull Run valve I illustrated earlier.

Alternating drinfield sketch

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Reader Comments, Questions & Answers About The Article Above

Below you will find questions and answers previously posted on this page at its page bottom reader comment box.

Reader Q&A - also see RECOMMENDED ARTICLES & FAQs

On 2021-04-23 by (mod) - cost of septic effluent splitters at the D-Box

American Mfg Bull Run™ Septic Valve, 4 Inch For PVC SCH 40 Pipe selling for about $85. U.S. cited & discussed at InspectApedia.com@Anonymous,

A typical septic D-box lid costs under $20. U.S.
to which
you would add the cost of labor to excavate, inspect, clean the surfaces, install, re-bury.

About your septic effluent splitter valve, if you are talking about a true valve, the cost can be $50 to $100 depending on model and features.

Here is an example

American Mfg Bull Run™ Septic Valve, 4 Inch For PVC SCH 40 Pipe selling for about $85. U.S.

On 2021-04-23 by Anonymous

how much does it cost to replace the distribution box lid?

On 2021-04-23 by Anonymous

how much does it cost to adjust a splitter valve

On 2020-02-23 - by (mod) -

Victoria:

Indeed we do NOT want surface runoff or ground water leaking into a septic tank nor piping nor D-box.

On 2020-02-23 by Victoria


Thank you so much for your help! After reading everything, that is what I am afraid of!! I will jot be able to get the lid opened for a few days, as it's suppose to be raining here, so I will be back within the next week, hopefully, with what's going on inside of the D Box.

Is there suppose to be a seal, or tight fit where the pipe goes into the D box from the septic tank? I believe I read somewhere that, on the cement boxes, like ours, they have a seal or asphalt around the piping? Just want to be totally sure what it's suppose to be like in there when I get it open.

Thanks again so much! I'll be back soon! :-)

On 2020-02-23 - by (mod) -

Victoria

Sorry to bring bad news, but if there were solids all the way to the septic tank lid underside then the tank was flooded and its outlet probably blocked by sewage; worse, having pushed solid sewage into the drainfield means a shortened or ended drainfield life.

Finding water in the yard, if it's coming from your house waste piping, tells us that the system is in failure.

It sounds as if you uncovered the D-box (which means you landed on the right page here at InspectApedia.com).

Certainly it'd be reasonable to have a plumber clear the line between septic tank and D-box but consider that if there are solids in that line then they've also been pushed to the drainfield itself.

Good going.

Now, opening the D-box will give us more diagnostic information.

If you lift the lid of the D-box and effluent is standing in the box and in its outlet pipes then the drainfield itself is either blocked or flooded (and in failure).

Bottom line:

No, effluent should not be backing up and leaking out of the D-box. That observation suggests that septic tank effluent is reaching the D-box but not being accepted into the drainfield.

On 2020-02-23 by Victoria

My husband and I just purchased a home about 7 months ago. Around Thanksgiving we noticed some water in a hole our dog dug. We ended up getting the septic tank pumped, which REALLY needed it. The person that pumped it said it looks as if it had never been pumped and had solids all the way to the lid.

Now, a month or so after, there's water again, we dug down and its coming from around a pipe thats going into a concrete box further down from the septic tank.

I've read most of the information on this site and believe that that is the outlet pipe going into the distribution box,

but my question is, should water be able to come out of the box from around the pipe from septic tank?

After all of the reading, it doesn't seem like it should, but nothing says so specifically. Also, if it isn't suppose to, what could the problem be? Or, shall I say, the cause?

On 2020-02-07 - by (mod) -

Oren

In the ARTICLE INDEX see SEPTIC DOSING SYSTEMS.

It ought to be pretty easy to install a pumping chamber and grinder pump combined with a dosing system control that simply alternates between two outlets to two separate tanks. You want to compare the cost of installing all of that with simply installing a larger septic tank or piping your two existing septic tanks in series.

On 2020-02-07 by Oren Reedy

Does anyone have a solution to split flow from an establishment (solids) into 2 septic tanks?


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