Mowing Mowing Septic tank

   / Mowing Septic tank #1  

MDSteve

Silver Member
Joined
Mar 13, 2002
Messages
182
Location
Clements MD
Tractor
Kubota 3710
I was wondering what is the largest tractor you would mow your front yard with if you had a septic tank there? Not thinking I have drove my 3/4 ton truck over it many times without any known damage. Or should I keep fixing the old craftsman to mow that area?

Thanks,
Steve
 
   / Mowing Septic tank #2  
I don't know, but here is what happens if you guess wrong/w3tcompact/icons/blush.gif.

Thank goodness this is my brother's work and house - not mine/w3tcompact/icons/grin.gif
 

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   / Mowing Septic tank #3  
Chances are.. if you are mowing your front yard with it.. the tractor is small enough... I have had my NH 1920 over my tank, and it weighs 35xx or so...
Keep in mind that there will be 4 weight bearing points ( tires ) and the weight from each of those sections will be applied connically down and out from the tire. If your tank is about 8" deep, the area the weight is being applied to is generally going to be larger* than the ground contact area of the tire. ( * soil material throws extra factor is to the load bearing calculation. )
To get down to the math side, most septic systems I've seen are cast out of 4000 psi concrete. The load carried at failure is going to be difficult to determine, because it is going to be different depending on where the load is carried on the tank lid. If carried near an endwall, the endwall will support a good portion of the load, decreasing as you move farther away from the endwalls.
Shear strength of concrete is going to be between 1/6 and 1/4 of the ultimate compressive str. Tensile strength ( though rarely tested in non-reinforced concrete, should be between 7 and 10% of the ultimate compressive str of the concrete.
Probably didn't help you any did it?/w3tcompact/icons/smile.gif
Soundguy
 
   / Mowing Septic tank #4  
The machine pictured is a motorized manlift or forklift.. those are rather heavy.... much heavier than tractors...Also.. factor in if the lift was carrying any extra load ( like trusses, etc ) Shock load is another issue. A static load is one thing.. but a sudden shock load ( loaded vehicle carying a swing load.. slams on breaks.. etc ) introduces other factors.

Soundguy


" don't know, but here is what happens if you guess wrong.
Thank goodness this is my brother's work and house - not mine "
 
   / Mowing Septic tank
  • Thread Starter
#5  
The tractor is a Kubota 3710. I try and keep most of the yard for a pasture but my wife wanted about a 1/2 acre so she can say she has a yard.
 
   / Mowing Septic tank #6  
Funny thing about liability law here in the US. After replying to these questions, I called around to some of the pre-cast producers our company deals with, and I could not get one of them to quote a 'crush' spec on thier tank lids.
I almost got into an argument with one place.. it would have been funny if not for the annoying factor. Here's how it went.." I called company 'A', and asked for load specs for their residential septic tank lids.
them -specs? what are you wanting to know?"
me- I'm just trying to get a ball park idea of what load the tank lid will carry before failure.
them- None..
me- ( slightly annoyed) can't be none... when installed, they ARE carying weight.
them- no they can't, they can't carry any weight at all...
me-( more annoyed ) Well... they are carrying about 8" of topsoil and vegitation... right?( approx 16 cubic feet= about .59 cubic yards at about 2000 lbs per cubic yard yeilds approx. 1187 lbs...... that IS weight? isn't it?
( At this point they became beligerant, and were of no further 'help'. )
Probably the same response if you asked someone to design and build you a rops structure.... too much liability to touch.. I guess... sad .. very sad..

Soundguy
 
   / Mowing Septic tank #7  
I was told by my excavator that installs septic tanks and often drives on/around them with equipment, that you should be safe until you reach the 7000 # mark.
 
   / Mowing Septic tank #8  
Depends on so many things, that there is no way to determine an answer to your question. My septic is 4-5' below the surface of the ground, but it is a 30+ yr old steel tank. I don't trust it with anything larger than my lawn tractor. But you can keep trying something bigger, and let us know what does or doesn't work. For sure, no one is likely to stick their neck out and tell you something is safe.
 
   / Mowing Septic tank
  • Thread Starter
#9  
Well I the house was built in 86 so the tank is not that old. I will send everyone pics once I get the tractor back from the 50 hour service. I am glad they don't need to be serviced every 50 hours I just got mine last month.
 
   / Mowing Septic tank #10  
Yikes..I bet that cost little in repairs to the building,and a bugger to get the fork lift out.
 
 
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