Tips for backfilling around sewer line repair

[OntarioGrass]

Hi , I had a section of sewer line replaced in the front yard, directly beside the house foundation. The depth is about 10 feet. I'm responsible for backfilling the hole, and I'm trying to determine the type of material to use. I've read recommendations for sand, gravel or soil, and I'm not sure which is best for ensuring the pipe is not going to be damaged by the weight of the backfill. Thanks in advance, my plumbing knowledge is pretty minimal!

 

[MicEd69]

Your primary concern is being sure the area under the pipe is not loose backfill that will allow the backfill above the pipe to put stress on the pipe.

A 10-foot excavation with no shoring is a little concerning.

"About 1,000 workers get hurt every year by excavation cave-ins. Of these, about 140 cause permanent disability, 75 cause death. The rate of deaths due to excavation is 112% higher than the rate for general construction. 38% of all excavation incidents are due to cave-ins. Trenches tend to collapse very quickly, leaving no time to react."

If the area under the pipe was not disturbed, you can use sand and compact it under the pipe. If they did dig under it and then put the soil back, you need to remove the loose fill and replace it with sand that you compact under the pipe. I'm pretty anal about protecting the surface of the pipe, so I always pack sand around the entire pipe as well. After the underside of the pipe is well supported and the sand is protecting the pipe, you can backfill the excavation with clean soil. At 10 feet of depth, you should really backfill in lifts of 12 inches or so. Add about 12 inches of soils and compact it with a tamper. You don't need a powered compactor unless you really want to. And you need to be careful when compacting around/over the pipe for the first couple of lifts. Again, 10 deep with a compactor can be scary and dangerous. If can do this over a few days, do 2 or 3 lifts every day and add water to the last lift, letting it set until the next day. Be sure to protect the hole so that children and animals don't fall in.

You could just compact the sand under the pipe and place sand over the pipe, then add loose clean soil to the excavation. Just be prepared to add soil to the depression that will happen over the next few years.

 

[OntarioGrass]

Thanks for this detailed response! There's about a 6 inch gap under the pipe, and no loose soil was put back in. Is there any particular technique to compacting the sand under the pipe, or am I just pushing as much as possible under and tamping along the sides? I'd also like to avoid any future issues, so I want to get this right lol! Point taken about the safety issues.

Thanks!

 

[Twowaxhack]

Those are the wrong type fernco boots for buried connections.

Pack your sand or dirt under the pipe nice and tight. Once you get to the top of the pipe and it’s packed nice and tight, backfill naturally with a shovel and let it settle itself, don’t pack it.

 

[Twowaxhack]

That appears to be a dangerous hole

 

[OntarioGrass]

Those are the wrong type fernco boots for buried connections.

Pack your sand or dirt under the pipe nice and tight. Once you get to the top of the pipe and it’s packed nice and tight, backfill naturally with a shovel and let it settle itself, don’t pack it.

What would be the correct type of couplings in this situation?

 

[Twowaxhack]

What would be the correct type of couplings in this situation?

https://www.supplyhouse.com/Fernco-...MIq9Xxs9TB_wIVOd7jBx1zZQADEAQYBCABEgKcZ_D_BwE
Maybe not this one, but the correct size of this “ type “

It’s fully shielded. This makes it near impossible for the pipe patch to deflect. That means sag out of alignment.

 

[breplum]

Extra heavy shielded couplings. Fern co-calls them strong back. Mission rubber calls them flexseal ARC. Do not do anything without placing proper shoring. You have an extreme safety hazard. You should also have a two way clean out right there.

 

[OntarioGrass]

Appreciated - Ill bring these issues to the plumber tomorrow....there is a 2 way cleanout a bit further up the pipe.

 

[MicEd69]

Appreciated - Ill bring these issues to the plumber tomorrow....there is a 2 way cleanout a bit further up the pipe.

I didn't look at the piping as your question was about the backfill, but indeed that is the incorrect Fernco for an underground connection.

But unless you fill this excavation in lifts and do some type of compaction, you will get settling in this 10-foot-deep excavation that will occur for years. And again, this appears to be a dangerous excavation so extreme caution needs to be maintained until the hole is less than 4 feet deep. OSHA would not allow this work activity without shoring, a multi-man crew, and a retrieval apparatus in place. They would also require air testing just to be sure there was plenty of oxygen and no flammable gases in this hole. This may appear to be going overboard on safety, but I just want to be sure you understand the extreme risks associated with this type of excavation and backfill operation.

 

[Twowaxhack]

We fill holes like that just like they do at the grave yard.

Mound the dirt up a couple feet and it settles over about 2 months here, we get a lot of rain.

There’s many ways to screw a ho……

 

[Twowaxhack]

Some contractors haul
The dirt off and fill it with a cheap concrete like substance……can’t remember the name. It gets hard and doesn’t settle, goes in like concrete.

 

[Twowaxhack]

It’s called “ flowable fill “.

No dirt, no tamping, no settling.

 

[Ludington]

I dont like the mounding up idea, they did that in my front yard over my septic drain lines. Been 30 plus years and they never settled, so now I have a roller coaster front yard. I really need to have someone come in and level it all out. Just don't want to start over with seeding the yard again. ... but , no humps please

 

[Twowaxhack]

I dont like the mounding up idea, they did that in my front yard over my septic drain lines. Been 30 plus years and they never settled, so now I have a roller coaster front yard. I really need to have someone come in and level it all out. Just don't want to start over with seeding the yard again. ... but , no humps please

Don’t worry, I’m not going to do the job. Do it anyway you want but dirt doesn’t take 30 years to settle if the dirt is over the original hole.

Facts, have sum.

 

[MicEd69]

Don’t worry, I’m not going to do the job. Do it anyway you want but dirt doesn’t take 30 years to settle if the dirt is over the original hole.

Facts, have sum.

Another way to fill the hole and not leave a long-term hump or depression is to surcharge it with an additional 3 foot of dirt. Then after a few months, you can remove the excess dirt and the ground will be level.

No, it doesn't take 30 years for the ground to settle, but it can and often does take 2 to 5 years depending on the soil. If you go around to a new subdivision a year or so after everyone moves in, there will lots of low places over utility runs.

And if you want to place a concrete mixture, flowable fill, over the sewer that won't settle, that works well. It does make it a little difficult to excavate should there be another problem at that location, however.

 

[Twowaxhack]

I’d want the job done correctly before it’s backfilled.

Those rubber couplings are not meant for burial that deep or really at all, although a foot or two isn’t a problem.

I’d bet dollars to donuts that patch will deflect in short order, especially if it’s compacted.

 

[MicEd69]

I’d bet dollars to donuts that patch will deflect in short order.

Absolutely! Even packing sand or dirt under the section replaced, there has to be "some" rigidity at the repair joint.

 

[Pipe Dreams]

Danger Danger Danger.

I would not enter the hold at all anymore unless shored.

at this point, fill with concrete until just over the pipe, let cure, then fill in with whatever

 

[Tom the Elder]

It’s called “ flowable fill “.

No dirt, no tamping, no settling.

Flowable fil is a good idea. If the amount of cement in the mix is correct, the fill will not settle but it cn be dug with a shovel. Pretty expensive though as it comes in a redi-mix truck.

A DIY alternative would be a wet batch of sand-cement mix. Wet enough you can be sure it will flow to fill the void under the pipe. Fill it up to at least the spring line. Way weaker than concrete but plenty strong for pipe support. Above that, pick your poison.