Pouring slab over septic line

[rynovt]

I'm hoping that some of you construction or building types can advise me on my new garage. The best place to put my garage would place the slab over the line that runs from our septic tank to our leachfield. It would cover about 24 feet of the line. I would like to pour either a monolithic or floating slab in that area. Has anyone done this? The system is brand new so I wouldn't expect having to mess with it for a long time. I do have nightmares about ever having to dig that line up once the garage is over it.

Thoughts?

 

[Kyle241]

I personally would not do this. Also are there any code issues with doing this? It can be done but that is a lot of weight on top of the pipe and all buildings settle. Also inevitably you'll need to get under there at some point and that will be a royal pain. I'm sure others will chime in as that is my personal opinion. Absolutely no other place to put the garage?

 

[Gary Fowler]

I wouldnt have a problem with putting a slab over the line assuming all the cleanouts are in place and not under the slab. You are talking about a solid line and not the field line I assume. If it was properly glued down, there is not any way for roots to get inside. Only time I ever had to dig one up was because the builder ran a trencher over the drain from house to city sewer line at my old house. I kept requiring rotorooting about every year and finely I had a plumber do a video scope on it and found the cut. @##$% contractors knew they hit it but just put a split oil can over the cut. Of course this was 30 years after the house was built and I was the second owner.
As far pressure on the line, that should not be problem either as long as the line is at least 12" under ground you could run just about anything over it and not hurt it. Just be carefull with the concrete trucks when they come in if the ground is a little wet because those things do put some soil pressure down.

 

[Aguanga]

I would obviously try to avoid it. How much fall is in the line? If you have enough fall, you can relocate the line to go around the new building location. When relocating, try to keep the new allignment beyond the bottom of the footing so that it does not fall with the load bearing area beneath the footing (typically a 1:1 slope away from the outside bottom corner of the footing). If you don't relocate the pipe and all of your load bearing walls are on the perimeter, you could also dig and expose your pipe within this same imaginary load bearing area where it crosses your footings. Once exposed, assuming that it's a conventional garage structure, you'd be OK with concrete encasing the pipe for 12" on all sides. Make sure you don't "float" the pipe when pouring the concrete around it (potentially creating a high point or reverse fall in a section).
However, you could also roll the dice that you'll never have a problem with the pipe. In the future you could replace the section of pipe under the garage later using pipe bursting, but that'll probably set you back $2-3,000 if you do all of the prep work for a trenchless pipe specialist contractor.

 

[/pine]

I would obviously try to avoid it. How much fall is in the line? If you have enough fall, you can relocate the line to go around the new building location. When relocating, try to keep the new allignment beyond the bottom of the footing so that it does not fall with the load bearing area beneath the footing (typically a 1:1 slope away from the outside bottom corner of the footing). If you don't relocate the pipe and all of your load bearing walls are on the perimeter, you could also dig and expose your pipe within this same imaginary load bearing area where it crosses your footings. Once exposed, assuming that it's a conventional garage structure, you'd be OK with concrete encasing the pipe for 12" on all sides. Make sure you don't "float" the pipe when pouring the concrete around it (potentially creating a high point or reverse fall in a section).
However, you could also roll the dice that you'll never have a problem with the pipe. In the future you could replace the section of pipe under the garage later using pipe bursting, but that'll probably set you back $2-3,000 if you do all of the prep work for a trenchless pipe specialist contractor.

If it is a solid line, not part of the leaching/percolating system it would no different than any other plumbing that is normally placed under a (house etc.) slab...hopefully it is at least schedule 40 or better and not the thin-wall piping...

 

[CurlyDave]

Go ahead and cover the line.

While the most appealing solution would be to re-route the line around the garage, it is actually more expensive than necessary.

Be certain that you have left a pathway to easily abandon the line under the garage if necessary and to re-route a new line around the garage. If you take this simple precaution, you have a much more appealing way out of a seemingly intractable problem if there is ever any need to dig up the old line.

 

[hosspuller]

Another thought is to bury another line parallel to the existing line. Call it a repair line. Just make sure it's well marked and known to anybody that follows in the years to come. Perhaps markers in the slab

 

[CNC Dan]

I'm hoping that some of you construction or building types can advise me on my new garage. The best place to put my garage would place the slab over the line that runs from our septic tank to our leachfield. It would cover about 24 feet of the line. I would like to pour either a monolithic or floating slab in that area. Has anyone done this? The system is brand new so I wouldn't expect having to mess with it for a long time. I do have nightmares about ever having to dig that line up once the garage is over it.

Thoughts?

it's too be avoided if you can. But if you have to, dig in a second pipe now, with the ends capped off. Use something permanant to mark the ends so you can find it in 20, 30 years. Then if the line ever fails, you have a spare in place, no digging up the slab.

 

[Stimw]

You don't have your location posted- frost line???? Footer depth?????
You don't say what material pipe is or depth. ???
Questions that need to be answered to give an educated answer.

 

[tessiers]

Aren't many buildings that don't have some sort of burried sewer lines under them. If you have problems in the future you re route the line, depending on inverts and diatance it could get costrly but then again you could always bore under the garage if you had too. I have worked construction all my life and if it is a new properly installed line and you have adequate foundation soil bearing I say go for it.

 

[tractorski]

I am very interested in this thread, I have the same situation.

Sent from my iPad using TractorByNet

 

[dave1949]

Another possible backup technique would be to run the existing line inside of a larger diameter and sturdy pipe. Of course you have to re-install the existing line to do this, but you will digging up the area anyways.

Seal the ends good so nothing can run into the larger pipe. If you have a problem later on, you should be able to replace the waste line by sliding out the old and sliding in a new pipe.

 

[CTMassey]

lots of good suggestions, in my opinion I would, as a couple others have said, run a spare "repair line"close to the existing line, sch 40, backfilled with 3/8 stone. If the line is from your tank to the field, the existing line may be sdr35, as sch 40 is not required(in my area anyway), fom the tank out. Large commercial buildings on slabs have intricate plumbing underneath, so it is certainly not a major issue

 

[kneedeep]

If you are sure the line to be covered is a supply line only and is not part of the Leach field it can be covered if deep enough for proper footing depth.

Supply only lines with cleanouts are under slabs everywhere. If it is part of the leach field, covering ot with a concrete slad/garage is not advisable as the ground is unstable (could be wet), will render that part of system inoperable and could cause settling /cracking of the slab.
However, the supply line needs to be Sch 40 PVC under the slab to the leach field.
Have you probed the line for depth in the construction area? Might be a good idea to locate the line direction and depth and mark accordingly for avoiding it with heavy equipment.

 

[BHD]

thirty six years ago I did just what was being discussed here, in a property I lived at,

there was no problems, until just a few years ago, my folks moved into the place when I moved out, and my mother planted some popular trees in the yard, about 15 to 20 foot from the building, now those trees have spread out roots, and apparently sent them under the building, as about once a year one needs to run a "heavy duty drain snake" type machine down the drain to clear it,

the line is belled Cast iron, if it would have been a solid and glued plastic line I do not think there would be an issue,

and the trees could be removed,

another party lives there now,

I really do not under stand the roots 20 foot from edge under the cement slab tho, as I would not think it would be that moist under there to draw the roots, (unless there was damage to the line many many years ago) before the building was built, the building or slab has not moved, there are no cracks in the slab.

 

[jgrieve]

Make sure to compact the fill properly

 

[radioman]

Many good advice and some iffys. Just like everyone says - as long the pipe is a service line to the tank or city sewers should be ok. If it part of a leeech feild, I'd contact your local septic professionals and ask them for opinions. How long was the pipe been in service when it was installed? When was last time you sent a camera in to inspect the pipe? You wouldn't want to replace it later after the slab been poured so replacing it now if it 40 years or older is cheap insurance policy after you have it scoped.

 

[ray66v]

I put my barn over the existing sewer line on purpose.

I put a full bathroom in there. :thumbsup:

 

[davedj1]

I am a builder and I wouldn't hesitate to build the garage over the pipe. Weight won't be an issue as the slab spreads the weight out enough. I've done it many times and never an issue. Think about all the sewer lines that are run across streets, under parking garages, stores, warehouses etc. etc.

 

[ilander]

it's too be avoided if you can. But if you have to, dig in a second pipe now, with the ends capped off. Use something permanant to mark the ends so you can find it in 20, 30 years. Then if the line ever fails, you have a spare in place, no digging up the slab.

I've marked beginning and endings of lines like you've mentioned. My method is to get a green treated 2x4 or 2x6, stand it vertical in the trench with the bottom end up against the end of the pipe. The top end of the board protrudes slightly above the trench. After back filling, the board can be cut flush with ground level. Finding the line end is easy, just carefully follow the board down to the bottom with the backhoe. The board will fall over, the line is exposed.

This method works great for running lines between two buildings. Start out at the first building and work your way to the second. When the backhoe front gets close to the second building, do what I said above, Then set the machine on the back filled trench and dig away from the second building until you get to the board. This eliminates the huge hole needed at the second building when digging from the side. Of course, be careful of cave ins on deep trenches.