slab over main pipe to septic?

[jpcjguy]

Hi all,

So we are revisiting doing a screen porch off the back of the house. I have some questions about the septic line that runs underneath the current patio.
Right now we have a paver patio that I would pull up and reuse somewhere else and do a stamped concrete pad.
This new slab would be over the main line from the house to the septic tank. So I am wondering if that is ok - or should I - before a pad is poured - replace it? or sleeve it or something? My nightmare is having an issue with the line and having to redo the concrete...
I have attached some pics of the current patio and where the line runs. I don't think it is too deep and once I pull the pavers, I have a one time opportunity to do something. What do you all think?
Thanks!

 

[The Cobbler]

depends on what's there now I would say . (age, material , overall slope & condition) would be a factor in my decision

 

[Junkman]

In our town where we have a septic system, you are not allowed to build over the septic line unless it is something like a deck that can be removed. All the piping in the house is PVC, but the town required cast iron from the foundation to the tank, so at some time in the future, someone is going to need to replace it. Next year it will be 40 years since we built the home, and I don't know what the life expectancy of cast iron is, but I know from my old home, that it does rust out eventually.

 

[Sumboodie]

Worst case you redo the slab or redo the pipe on the side of the slab, not the end of the world.

 

[The Cobbler]

reroute the septic line to the side of the house away from the pad if it ever becomes a problem

 

[PCustoms]

reroute the septic line to the side of the house away from the pad if it ever becomes a problem

I don't think that's typically possible.

 

[Sumboodie]

I don't think that's typically possible.

All depends on the layout of the place. Not uncommon around here to leave the old tank and piping in place and just put a new one a bit away from it. Crush the old tank and fill with dirt.

 

[jpcjguy]

In our town where we have a septic system, you are not allowed to build over the septic line unless it is something like a deck that can be removed. All the piping in the house is PVC, but the town required cast iron from the foundation to the tank, so at some time in the future, someone is going to need to replace it. Next year it will be 40 years since we built the home, and I don't know what the life expectancy of cast iron is, but I know from my old home, that it does rust out eventually.

Pretty sure it is not cast iron. I would have to go back in the crawlspace and double check - it is black pipe as you can see in the pic but looks like PVC - did not army crawl all the way over there. It is also a 1993 build. So I don't think I am worried about rusting out. I guess splitting or cracking would be my issue....

 

[PCustoms]

All depends on the layout of the place. Not uncommon around here to leave the old tank and piping in place and just put a new one a bit away from it. Crush the old tank and fill with dirt.

Well yeah, new tank and possibly new field he could move the line..

If it were me I'd cover the line, making sure I'm not covering the tank. On the very small odds there is an issue, you'd have to bust up some concrete. Not the end of the world and likely not really a concern.

I would NOT do this with clay or cast pipe.

 

[jpcjguy]

Well yeah, new tank and possibly new field he could move the line..

If it were me I'd cover the line, making sure I'm not covering the tank. On the very small odds there is an issue, you'd have to bust up some concrete. Not the end of the world and likely not really a concern.

I would NOT do this with clay or cast pipe.

That is what I was thinking - no way with a clay or cast pipe. Just wondering if it would make sense to replace it now - it is 29 years old or even drop a 6" or 8" pipe in the ground and run the 4" drain pipe through it. A whole lot cheaper now than once a slab is poured...

 

[CraigStu]

My first question is will the new screened porch be larger than the current pavers. I suspect that you can get away w/ a lot w/ just a paver patio. But doing a structure w/ foundation and typical stick built and roof, I think there will be codes saying how close you can be to the septic tank. I know that in northern Va that was a problem for one possible location for our add-on detached garage. I would also not be surprised if there are limitations as to what can be built over your septic line to the tank.

 

[jpcjguy]

My first question is will the new screened porch be larger than the current pavers. I suspect that you can get away w/ a lot w/ just a paver patio. But doing a structure w/ foundation and typical stick built and roof, I think there will be codes saying how close you can be to the septic tank. I know that in northern Va that was a problem for one possible location for our add-on detached garage. I would also not be surprised if there are limitations as to what can be built over your septic line to the tank.

Great question and point. The footprint would be same or maybe a foot or two larger. Luckily I am in a rural county - Goochland - and I called and talked to the inspectors and they said no problem with my plan. I will not be over the tank itself, just the line. I am very familiar with its location as I have a 1/2 bath in my detached and ran a 200 foot drain line and tapped into the house line about 1-2 feet from the tank. Of course, I plan to have a face to face with the inspector -whether in person at my property or in the office with a ton of pics to ensure they clearly know what I am doing.....

 

[Junkman]

Pretty sure it is not cast iron. I would have to go back in the crawlspace and double check - it is black pipe as you can see in the pic but looks like PVC - did not army crawl all the way over there. It is also a 1993 build. So I don't think I am worried about rusting out. I guess splitting or cracking would be my issue....

You might have ABS pipe in the ground. It is similar to PVC. I looked up its life span, and the internet says 50 years, however, in the 1980s, there was some questionable manufacturing process that led to California putting a ban on the product. It might be advisable to reroute the line, and abandon the old line under the new addition.

Why is ABS pipe no longer used?
The State of California has banned the use of “regrind” or recycled plastic resin for use in ABS drain-waste-vent pipe. The new law stemmed from major problems with pipe failure of recycled-content ABS pipe made by several companies during the 1980s.

 

[southalabama]

I’d joint my concrete so that a section over the pipe could be easily removed in the future.

 

[jpcjguy]

You might have ABS pipe in the ground. It is similar to PVC. I looked up its life span, and the internet says 50 years, however, in the 1980s, there was some questionable manufacturing process that led to California putting a ban on the product. It might be advisable to reroute the line, and abandon the old line under the new addition.

That was my thinking - I have an opportunity to replace the line with better material - we are talking about a 20ish foot run. Granted I should get the numbers off the pipe that I can see in the crawlspace and actually determine what I have and go from there. Great points everyone!

 

[mcbane]

If it is a straight run, whenever it fails it can be replaced by pipe bursting. Hydraulic expanding plug is pulled through, expanding every few inches. And a HDPE line is pulled in behind the expanding unit.

Cast iron and ABS both break as easily as glass so a very straightforward repair. Only thing to check is if you live in a big union city HDPE may be banned due to low labor hours per unit length.

Edit: technique called pipe bursting, if you want to look it up

 

[Sumboodie]

That is what I was thinking - no way with a clay or cast pipe. Just wondering if it would make sense to replace it now - it is 29 years old or even drop a 6" or 8" pipe in the ground and run the 4" drain pipe through it. A whole lot cheaper now than once a slab is poured...

Wouldn't be a horrible idea. Already need to dig some for doing concrete, so what's digging 6-7ft down to replace the **** pipe?

 

[jpcjguy]

Wouldn't be a horrible idea. Already need to dig some for doing concrete, so what's digging 6-7ft down to replace the **** pipe?

actually digging 2-3 feet - judging by depths...

 

[Sumboodie]

actually digging 2-3 feet - judging by depths...

Gotcha. I'm used to burying deep so it doesn't freeze. Sort of forget that some places don't really freeze!

 

[Wheelingit]

I would replace the line now. I have seen ABS pipe shear or crack for no apparent reason.

 

[couch67]

if once you start excavating and see the pipe, maybe. But if the pipe is lower than your ground prep, I would not disturb it as moving the soil around it and replacing is going to have more impact than just leaving it be.

 

[Lynden]

If it is a straight run, whenever it fails it can be replaced by pipe bursting. Hydraulic expanding plug is pulled through, expanding every few inches. And a HDPE line is pulled in behind the expanding unit.

Edit: technique called pipe bursting, if you want to look it up

+1 on pipe bursting. I had my 4" cast iron sewer lateral replaced three years ago using pipe busting. The total length of the replaced line was about 70 feet and the depth was 3 to 4 feet. They went from my crawl space, under my driveway, and under an area of landscaping to the 6" public sewer lateral at the rear of my property. They dug four small access pits -- one in the crawl space, two to intercept and replace a sewer line coming from my garage and the last one at the public sewer. No trenching was required. Cost was $4000 of which the city paid $2000 (sewer lateral replacement program).

 

[Showkey]

Very common for the septic line or line to the drain field ……..to go under a deck, patio or drive way.
My drain field line goes under my asphalt driveway to the shop.

My pipe from my well to the home goes near or under the patio turned screen porch. If it goes bad there will be a need to reroute. It’s over 10‘ feet deep and comes through the basement floor not the wall. Even if not under the screen porch stairs walk way and other things will be in the way.
All of this is not my doing but it’s all legit.

 

[ATC]

I’d joint my concrete so that a section over the pipe could be easily removed in the future.

I came to say this. If OP was planning to do a stamped concrete floor anyways, it would be easy to hide in the design.

Our house is 52 years old, and still has the original cast iron pipe...even has a few trees growing through it. Runs over 100' away from the house to the tank.

(knocks on wood)

 

[firebirdparts]

O.P., I guess you see this, but there's been some confusion in these replies between "A septic line" and "A line going to the septic tank". It sounds to me like you are talking about "A line going to the septic tank."

 

[CombatNinja]

Yeah. He's talking about the 'blackwater' line from the house to the tank itself. The junction box and leach field will be far enough away that his patio slab will not be a concern.

If I were doing this project on a 30 year old pipe, I would replace it without even thinking much about it.

 

[Showkey]

Deleted

 

[Debcrow]

When I got ready to pour my slab for the shop, it ran over the top of the line TO the septic tank (but not over the septic tank).
I hand dug up the old septic tank line. Put a clean out fitting at both ends of the existing line outside of the new slab.
I also laid in a new line next to the old one with clean outs on both ends of it and capped it off on both ends in case I had to ever switch out lines under the slab. Not expensive using plastic pipe.
Good insurance and peace of mind.