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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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.
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.
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.
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.
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.
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.
Reader 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]
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
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
Watch out: driving over a cesspool risks sudden collapse and even a possible death or injury.
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
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(Sept 27, 2012) Clark said:
I am hoping to drive a 2220kg Thomas loader over a septic system for the removal of tree brush. We plan on laying down thick plastic pads to disperse the weight of the loader. What is your opinion on the risk of this action?
(Dec 11, 2012) beth said:
designing landscape for nursing home. is there any type of material that can be used for a walkway so that it can cross a leaching field?
Beth, in my opinion a walk across the septic field should cover so little area as not to interfere with field function. I'd use dry laid slate if not for the worry of trip hazards for your occupants.
But I have a secondary worry. Make sure that during construction heavy equipment is kept away from the fields to avoid damage. As some readers comment (below) "you can't construct a 'path' over a septic tank drainfield. But "path" in the U.K. can have a very different meaning than in the U.S. or Canada. In the U.K. there are old right-of-way common access pathways across otherwise private land. These paths can have significant usage - which is why one would not route an access path across a septic leachfield or soakbed. But on private property where there is limited access the issues are less severe and walking across a working drainfield should not harm it.
(Jan 9, 2013) Maureen Webb said:
In the UK, you cannot construct a path over a septic tank drainfield - Section H2 of the Building Regulations.
A path "constructed" over a drainfield, especially if it means carrying equipment or traffic that compacts soil, would, I agree, be a bad idea.
On the other hand, for a properly built and working drainfield, a human (not livestock) just walking over the field, will be harmless.
(Dec 22, 2012) Great page said:
Very informative site, thanks for your time.
(Mar 27, 2013) Bill said:
Can you give advice. A neighbour has dug up half our septic tank filter system (which is on their land) and damaged one of the pipes leading from the septic tank - which they said they'd made good. They were putting in foundations (within 15 m of the filter system - which the council allowed). They've driven all over the filtration site. The council won't get involved and are now saying that water is leaching from our filter system onto their land and they're going to take action against us.
What a mess. Your septic system is almost surely illegal right - in all of the local sanitary codes I've seen you are not allowed to dispose of your septage nor septic effluent off of your property (onto a neighbor.)
You will want to relocate your septic tank and other components to be completely on your property as well as far enough from property boundaries and other site features to be code compliant.
(Mar 25, 2014) Tricia Williams said:
Can I place a rock garden over part of my leach field? I want to put it right in the center and then plant bermuda grass over the rest of the field, around the rock garden.
Yes and no. Yes if you're talking about light-weight stuff and no use of heavy equipment to set it in place and no deep-rooting plants.
Please see PLANTS & TREES OVER SEPTIC SYSTEMS at
June 30, 2014) Alison said:
We want to create a sports area for the grandkids when they visit and the flattest and most unused area of our property is over the septic field. Could we add more topsoil, turf it and then use it for games such as badminton, croquet, bocce, horseshoes and golf putting? Obviously we would not dig any holes within the field itself and use would be infrequent.
In my OPINION, normal human foot traffic over a working (not leaking, not unsanitary) septic drainfield should not damage it.
BUT the construction of a play area over a septic field by using equipment that might compress or disturb soil or break a buried pipe risks costly damage
AND adding topsoil can seriously interfere with proper drainfield operation by reducing the oxygen level in the soil below, thus reducing the level of aerobic bacterial treatment, thus leading to discharge of contaminants to the environment. Adding topsoil also can reduce the disposal of water in the effluent dispersal system via evaporation.
(July 21, 2014) Steve said:
Could I erect a building on posts above our field bed knowing exactly where the lines are and placing the posts to avoid them?
(July 23, 2014) (mod) said:
You might be OK with the posts if you stop there.
I would not build a structure over a drainfield. What happens when you need to repair or replace the fields? And what are the chances that we an build a structure without ever driving machinery close-by, ruining the fields?
(Sept 18, 2014) Ann said:
Recently while moving my son backed the moving van over the septic area. It was there only a short while before it was noticed and was asked to move the truck. How can we determine if any damage was done?
good question, Ann,
If your system has a distribution box, open the box and see if there are signs of backup or failure to accept effluent in one or more of the lines.
Beyond that, I don't know a good answer. In my OPINION if there is no sign of blockage such as a sewage backup, new odors, or wet areas developing in the drainfield or near it, then it's not worth digging up the spot to see what happened.
If you do find signs of a backup at the D-box or on the ground surface or in the septic tank and were looking for a broken crushed drainfield line, then I'd dig and look at just where the van drove over the field trenches.
(Oct 21, 2014) Mike Allara said:
Can I build a small tee box on my septic field at my golf course? the field is reasonable large and I would not look to add anything bigger than 4 x 5 with some elevation.
(Oct 21, 2014) (mod) said:
A tee-box indeed sounds like a golfing system component. If you mean a tiny receptacle to accept golf tees, just put a birdhouse-sized box on a little post and don't drive the post into a drainfield trency.
If you mean a rain shelter or larger structure, it'd be smart to keep such structures away from the fields. For that matter, we might worry about field compression and damage if people are driving golf carts over it too.
If you mean the distribution box, the size needed is determined by the number of connections the box must feed. Or you could daisy-chain several.
24 Feb 2015 Nina said:
The septic tank left the drain lines lying on top of ground. It looks awful!
He also put the lines in our driveway! He is supposed to be a professional
Our septic tank guy left the drain lines on top of ground! Is this acceptable?
He also put the drain lines in our driveway!
Nina I don't have a clear picture of what the heck is going on but it sounds as if a septic field installation is unfinished.
Certainly we wouldn't put a drainfield under a driveway, but pipes (rated to withstand the weight of traffic) might have to cross a driveway to carry effluent to a drainfield or septic tank.
24 Feb 2015 karen said:
We have grass and couple of picnic tables over our leach field but we would like to put some more dirt or some mulch because the roots from trees and the fact that grass doesnt grow too well from limited sunlight in this area. We were thinking of putting mulch, small stones or rubber mulch down which is easy to walk on. What material is okay to put down over a leach field??
What we want to avoid over a leach field are plants that might send down deep roots that invade the system and clog it, and of course we don't want to drive equipment over the field while delivering anything heavy as that too can damage the fields. Your citation that there are trees over the septic fields is itself a worry.
a complete guide is at PLANTS & TREES OVER SEPTIC SYSTEMS
If you were to replace a small area of grass with stone, say around a picnic table itself I doubt that'd have a measurable impact on the septic system. But if you were to add gravel over large areas, while transpiration (evaporation) of effluent may continue, you're losing the benefits of moisture movement that is achieved by the grass that was there - a result is a wetter lleachfield and a shorter life.
(Apr 7, 2015) Ruth said:
Someone just drove over our septic area about 4 feet from the riser. How soon should we notice a problem in the house (gurgling drains,etc.) if damage to the line was done?
I can't say, Ruth as we don't know enough about your septic system piping layout. If an exit line between septic tank and drainfield were totally blocked and if the septic tank has no leaks, you'd notice backing up drains as soon as you've run enough wastewater to fill the septic tank that last few inches to its lid and to fill the piping between tank and house - normally within a day. But a cracked or partly crushed line could still be damaged but take months to show up as a problem since it can take time for soil or roots to fill in the damaged piping.
LInes buried very deeply are less likely to have been damaged by a drive-over.
Since you know exactly where the line was driven-over, you have the option of digging to look.
(July 15, 2015) Dave said:
Can I create a walkway (patio stones/interlock) over a tile bed (in Ontario Canada)
The walkway would only be from 4 to 6 feet wide and would cross the tile bed
You've probably read that in general we don't want to cover the absorption bed and we don't want to compress soils nor drive over it. I don't know the total size of your particular tile bed but I speculate that the area that is covered and thus lost to transpiration / evaporation by simply hand-laying interlocking pavers to walk over the area would not be significant and so may be just fine. MAYBE.
If you are going to drive equipment over the "walkway" then I'd vote against it. If you are simply going to have people and maybe pets walking on it that's likely to be ok.
(July 16, 2015) Dave said:
Thank you for your info. A little more info on the possible project.
The walkway would only be for people and pets to access the home(looking to relocate entry door to home) also I was thinking that I could use a combination of flagstone and clear stone to create the walkway. Would that be acceptable?
Would that affect the tile bed, especially in the winter (we get temperatures as low as -40 Celsius)
The weight of flagstones and people walking a narrow path across a septic field shouldn't harm it;
(July 20, 2015) Marg said:
Would it be Ok to drive a bucket truck on to the lawn on planks for a short period of time, just long enough to pressure wash the peak of the house, let it dry and paint it?
If the weight of the truck is sufficient to compress soil or worse to break a buried line, that takes only seconds. So "a short period of time" won't avoid trouble.
IF and I do mean IF your contractor can put down enough heavy 4x8 sheets of plywood to distribute the weight over a larger area than would be done by planks you might get away with it. Use 4x8 foot plywood of 5/8 or better 3/4" thickness. Planks are more doubtful.
OR you can make sure that the route of the truck is not over piping or soakaway bed trenches.
(Sept 15, 2015) Joseph said:
Is it common to build a septic system where the pipes will be laid under a road? What problems could occur over time. If there is no other option, what measures should be taken to prevent damage to the system?
If we're discussing solid piping to move effluent to a drainfield, proper pipe type (schedule 80 or better), depth, trench preparation and backfill can protect the pipes from damage from the road above. We wouldn't put part of the drainfield itself under a road - it would lose its evaporation capacity for that area and repairs would be quite costly.
(Sept 25, 2015) David N said:
I just ran a large mini excavator across a drain field perpendicular to pipes . The machine had tracks not tires and the tracks are at least 8 foot long . Since it had tracks it didn't sink into areas where pipes were ( I could see where soil was lower where the pipes were buried) I'm worried that damage may have occurred, how do I tell if it was damaged ? Only crossed it once.
All the worrying is my profession I have to admit that not every possible catastrophe is going to happen. Your septic fields may be okay. It depends on
If there is a distribution box upstream from the leach field lines that you crossed you can open that box to watch for signs of an effluent backup.
To go further would require excavation either at the end of the leach line or in the area where you drive across it before digging up such lines to look for damage I would watch the d'box as I said and I would watch for effluent break out or back up anywhere in the system.
if you don't see those problems then I think the further excavation is probably not justified. Do keep us posted on what you see.
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