Septic system collapse and truck rescue (C) Daniel Friedman

Do not drive, pave nor park over Septic System Components
     

  • DRIVING or PARKING OVER SEPTIC - CONTENTS: Is it ok to have septic piping or a septic tank under a driveway or parking area? Can we drive over septic piping or tanks?Can we drive over the drainfield? Can we build, pave, or put astroturf over a septic drainfield?
  • POST a QUESTION or READ FAQs about drainfield damage due to vehicle or equipment traffic
  • REFERENCES

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This article explains the problems that occur if septic components are located under a drive or parking area. We explain why you should not drive cars, construction equipment, or other heavy machinery over the septic drainfield and in some cases also not over the septic tank.

Our page to photo shows a big effort underway to pull a dump truck out of a seepage pit. Luckily no one was injured but the cost of extracting the truck and repairing the septic system was significant.

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Do not drive over the septic tank, septic piping, or septic drainfield.

PHOTO of a septic seepage pit collapse when a truck drove over it.Unless special provisions have been made such as protection of sewer piping and septic tanks from damage, vehicle-rated septic tank covers, or similar steps, do not drive vehicles over septic system piping or septic tanks.

Driving over septic tanks, septic piping, or drainfields risks costly damage to the septic system and may also be dangerous.

The bulldozer in our photo (left) was called to help remove a truck which drove over septic system components leading to a surprise collapse.

A property owner may not immediately recognize a septic system problem when piping has been run below a driveway, as crushing and blockage of the line may not happen until a heavy vehicle enters the driveway (such as the loaded septic pumping truck arriving to pump the septic tank). Or a septic line may be broken, permitting soil or roots to enter to complete the clogging process.

Watch out: as we report at SEPTIC TANK ACCIDENT REPORTS, driving over and damaging a septic tank cover or lid can result in a later cave-in, fall-in, or extremely serious hazards. While it is possible to purchase septic tank covers that are rated for withstanding heavy loads, even vehicles, as-installed residential septic tank covers are not normally capable of withstanding such traffic.

Also see SEPTIC & CESSPOOL SAFETY.

How do we run a sewer line under a driveway to get to the septic tank?

Photograph of new septic line house to tank

If a septic line must be run under a driveway, for example to pass from a building to the septic tank, the line must be protected by choice of materials (schedule 40), or placed in a covered and protected trench at adequate depth (such as with concrete covers over the trench) to avoid damage to the piping.

Our photo (left) shows a new sewer line being installed down a hillside, connecting a house to its septic tank.

The original terra-cotta sewer line lasted for decades until the building owner (DF) hired a landscaping company to mow the lawn. The fourth time that a heavy lawn mower drove over the original sewer line it was crushed and broken, leading to a costly sewer line replacement job.

The new sewer line was bedded in sand and protected from damage.

If a sewer line is run below a drive or parking area without proper choice of materials, protective measures, etc. it is an improper installation likely to fail.

Also see CLOGGED DRAIN DIAGNOSIS & REPAIR.

Can a septic tank be located safely below a drive or parking area?

Photograph of  rusted out and dangerous steel septic tankIf a septic tank is to be located below a drive or parking area, it too must be properly designed and protected from collapse.

The tank must be constructed of proper materials and provided with a cover rated to withstand the weight of heavy vehicles.

 

If the septic tank is steel, site-built, home-made, or even pre-cast concrete but lacking a cover rated to withstand vehicle traffic, driving over the tank risks collapse and even a potential fatality.

Our photo (left) shows a rusted-through collapsing steel septic tank cover that nearly led to a fatality to a home inspector.

See SEPTIC TANK DESIGN STRENGTH SPECS for details about the strength requirements for safe septic tanks, cesspools and drywells.

Photograph of a collapsing, impacted, failed home made septic tank.

Home made or "site built" septic tanks often have a cover made of wood or other flimsy materials, and depending on the tank construction (dry-laid concrete blocks or stones) the sides may also be likely to collapse if exposed to the weight of even a small vehicle.

The site-built septic tank shown in our photo (left) was collapsing as well as impacted with solids.

Driving even a lawn mower over this tank was likely to lead to a catastrophe.

Can a septic drainfield be located below a parking area, pavement, driveways, patios, decks, or other structures?

A septic drainfield should not ever be located below a driveway or parking area.

Driving or parking on a drainfield will prevent proper drainfield operation due to soil compaction and also due to loss of proper evaporation of moisture through the surface, as well as almost certainly leading to crushed broken piping. In sum, driving over the leach field in any vehicle larger than a child's bicycle is a bad idea.

Heavy vehicles may actually crush buried leach field lines, or they may compress the soils around the leach field, either of which leads to failure. Driving on or parking on leach fields will destroy them.

Paving over a drainfield, or installing patio stones or astroturf or any other material that blocks proper soil transpiration interrupts the evaporation of moisture from the drainfield, interfering with its ability to dispose of effluent. Furthermore covering a drainfield may result in inadequate soil oxygen, thus inadequate bacterial action, thus inadequate treatment of septic effluent, thus leading to ground water and possibly local well contamination.

LARGER VIEW of this
costly surprise caused by building a swimming pool over the drainfieldBuilding any structure over a drainfield risks damage to the drainfield from:

  • Vehicle traffic during construction
  • Broken drainfield pipes due to excavation for piers, footings, or other structural supports
  • Covering the soil, blocking transpiration and oxygen
  • And construction over the drainfield may make it impossible to later repair it when needed.

Our photo shows what happened when a swimming pool was constructed over the edge of a septic drainfield in Poughkeepsie, NY. The gray water shown leaked from the drainfield onto the pool perimeter when the homeowners did their laundry.

Citation of this article by reference to this website and brief quotation for the sole purpose of review are permitted. Use of this information at other websites, in books or pamphlets for sale is reserved to the author. Technical reviewers are welcome and are listed at "References." This is a chapter of SEPTIC SYSTEM INSPECTION & MAINTENANCE COURSE an online book on septic systems.

Generalizing the Reasons to Keep Equipment, Grazing Animals, Paving, Coverings and What Have-You Off of Septic Drainfields

NiceRink ice skating rink (C) Nicerink 2013 used with permissionReader Question: I would like to put a skating rink in my yard over the septic field (mid-Dec. to mid-March, i.e. northern Illinois) because it is the flattest part of my yard. I read everywhere on the internet and your site that one shouldn't put "anything" on top of a drainage field, at least the channels where the pipes ("tiles") are buried.

Photo at left: a NiceRink™ ice skating rink installed in a level area, photo used with permission. [Click to enlarge any image]

My question is exactly how a skating rink can damage field. Has research been done on this specific situation? Is the problem of a skating rink perceived or real? I haven't read of a failure due to a skating rink, though skating rink are relatively rare. I thought about the various issues: weight and permeability. Are there others?

[... content and detail moved to ICE SKATING OVER SEPTIC]

Reply: worries arise if building a skating rink atop a septic drainfield

Regarding your assertion and question

My question is exactly how a skating rink can damage field. Has research been done on this specific situation? Is the problem of a skating rink perceived or real? I haven't read of a failure due to a skating rink, ​​

​​Of course not. The number of possible SNAFUs humans can come up with is near infinite. We are not likely to find a study of skating rinks over septic drainfields because of their rarity. And some reasons for their rarity may be founded in common sense: the various objections to placing anything over a drainfield or soakaway bed can be generalized so that a requirement that experts explicitly address everything imaginable that one could place and should not place in that location is, with respect, well I'll leave out the adjective.

The reasons to stay off of a drainfield, including keeping equipment from driving over the septic fields in just about all regards are outlined at SEPTIC FIELD FAILURE CAUSES

Details of the pros, cons, & warnings about building a temporary ice rink over septic fields are found at ICE SKATING OVER SEPTIC

Cesspool Cover Strength & Safety in the U.K.

I have an extra large cesspit serving 2 properties on my land (19m x 4m) and is a pit only no outlet . Its brick built and was installed early 70’s, it has 2 chambers running back to back, and has a concrete cover on it which spans the whole length and width of the tank having 2 cast iron lids for emptying in the middle.

Question is – I inherited this with house from my Grandfather who used to drive over it with a small vehicle to get to his garage when the pit was still under a lawned area.

Could you please advise if you would consider that this was the type of cess that was constructed for driving over, and would still be ok??? - L.H. 3/25/2014

Reply: warnings about driving over the cesspool

Watch out: driving over a cesspool risks sudden collapse and even a possible death or injury.

  • Your system has too many unknowns for anyone with any sense to promise you that it is safe. Here are some of the variables that are apparent just from your message:

My advice is to stay off of the cesspool entirely until it has been excavated and its construction and strength have been evaluated.

We moved the full text of this question and its answer to SEPTIC TANK DESIGN STRENGTH SPECS

 

Continue reading at ICE SKATING OVER SEPTIC or select a topic from the More Reading links shown below.

Or see

SEPTIC TANK DESIGN STRENGTH SPECS

SEPTIC TANK COVERS

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DRIVING or PARKING OVER SEPTIC at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

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