should I panic about the ground sinking over my sewer line?

January 9, 2009 10:50 PM

the ground above my sewer line sank about 4" while I was at work today. There's no smell. Do I need to get this fixed on Saturday, or can it wait until Monday?

The house was built in 1947, and I bought it 2 years ago. The was some depression in the ground over the sewer line when I bought the house, but until today, it stayed about the same, so I just figured the ground had settled and never been leveled off. I live in Oregon, and it's been raining a lot (duh). I'm planning on staying with friends ~2 hours away on Saturday night, so I can shower at the gym and get through the weekend without sending anything down the drain. I left vmails for 2 plumbers, but neither of them had an emergency number.... is it OK to just get someone here monday morning? do I need to cancel weekend plans?

posted by comah to home & garden (12 comments total)

Did it sink 4" over the entire run, or just in a small spot? Either way, it doesn't sound good.

You'll probably save a lot of money if you wait until Monday, enough that you'd still come out ahead if you stayed in a hotel so you didn't have to run anything down the line. A neighbor had a sewer line break. They had an emergency plumbing crew come out who worked until midnight or so to fix it. The overtime bill was huge.
posted by Good Brain at 11:23 PM on January 9

Yes, you'll save money and no, I wouldn't worry about waiting especially since you're going to not use it.It does sound like it's possible you'll have to wait a bit longer--if the first time you talk to someone is on Monday morning they may schedule you later.

When I was a strapping teenager, we had some suspicious green patches on the front lawn (in a house of the same vintage) and I was dispatched to investigate. I must have dug for days, in the hot Southern California sun, with a heavy digging bar that my scrawny self could barely lift at the end of the day. The soil was really more rocks than dirt. I discovered I made it to the pipe when the digging bar went clean through it. The pipe was indistinguishable from the surrounding dirt in texture, although it had a slightly different color. It simply looked like a hole through the dirt.

I'm told that plumbing of this vintage was sometimes aluminum because of the war scarcity of iron, but I don't know if that's correct. I would imagine aluminum would corrode pretty badly down there; what I saw was pretty bad--almost like clay drain tile or something.

But to reiterate, it's not going to get any worse sitting there. It will be fairly expensive, so you might as well not pay overtime.
posted by RikiTikiTavi at 11:36 PM on January 9

I used to work for an engineering company in Winnipeg that did sewer line inspections and remediation, but without seeing it I couldn't really say for sure what the issue is.

Most likely, one of two things happened: either the service that links your house to the main sanitary line that runs down the middle of the street has collapsed, or it has developed a significant crack.

In the former case it does what you'd expect, a collapse would just crush the pipe under the resulting soil and create a depression as you describe. If it's a crack, however, it means that wastewater passing through the pipe and over the crack will leech the fine soil materials near the pipe into the actual pipe, and dump them in the sanitary line. This creates a void above the pipe which gets larger and larger as more of the fine soils are washed away through the crack.

If it's just a sewer line then I think you can wait, there's not much that can cause more physical damage than a depression on your lawn since the service is probably fairly small. I don't know what the regulations are, though, on having a broken service on your property. You might be required by law to get it fixed in some amount of time, who knows.

We had a guy cleaning catch-basins on a 4-lane road in the middle of the night, and he noticed a hole in the road the size of a playing card. He shone a flashlight in, and beneath the layer of asphalt was a void under the road the size of a shed. For however long, the catchbasin overflow line had been cracked and just sucking the soil from under the road whenever it rained, until it was just asphalt that was keeping the road level. If the road had been older or thinner pack, a car would have gone in, easy.

Just a dumb story, but I'd get it checked out, they should be able to scope it with a camera and figure out the issue without destroying your lawn right away.
posted by geodave at 11:50 PM on January 9 [4 favorites]

You might want to contact the local sewer agency first. The county I used to live in (in California) always told its customers to call them for any sewer problem, even if it was on your property.
posted by sageleaf at 11:59 PM on January 9

they should be able to scope it with a camera

This will not be cheap: we had a 3'x'5'x4' hole appear in our yard and brought a couple of plumbers in to see if they thought it was water-line or sewer-line related, and we were quoted between $200 and $500 to run the camera.

(In our case, it looks---we hope---like it's not sewer-related but rather some weird run-off issue. But it's not exactly above our sewer line, either.)

For what it's worth, as I recall from what the plumber told us, if it was really your sewer line totally busted, you'd be able to tell, because stuff would back up. If it's a crack, then you would expect some mud to get into the line. Is there a poky-up pipe somewhere in your yard? We had one and you could take the top off and look at the water going out, so the plumber had me run a bunch of water in the sink (connected to that line) and it was totally clear---no mud, so we think no break. (But as you can tell, I'm plumbing-confused.) This was a guy from a roto-rooter-type place.
posted by leahwrenn at 5:10 AM on January 10

Read up on Orangeburg pipes.
Every failure like this that I have ever seen was due to the use of this.
The age of the houses were similar. Talk to your neighbors about their plumbing.
Wait until Monday but do not use your water (toilet, dishwasher, clotheswasher, shower, etc.). Stay at a friend's or take little trip.
posted by Seamus at 7:10 AM on January 10

Also, check with your sewer company...they may have a program for replacing your lateral. Here in St. Louis, everyone pays a line item on their sewer bill that goes into a fund to cover half of the cost when the homeowner needs to replace the lateral.
posted by notsnot at 7:55 AM on January 10

leahwrenn posted: This will not be cheap: we had a 3'x'5'x4' hole appear in our yard and brought a couple of plumbers in to see if they thought it was water-line or sewer-line related, and we were quoted between $200 and $500 to run the camera.

Considering the costs for a plumber to dig down to the pipe to see what the problem is, yes, that is cheap.

I'm curious as to how the OP knows this is related to the sewer line? There are plenty of utilities that come the a typical house underground. Water, gas, and sewer are the typical three that are underground. Sewer pipes are usually the deepest utility and depending on if you have a basement could be more than ten feet deep below ground. Even if the sewer line had somehow collapsed you probably wouldn't see any ground depression unless there was also a water service break which was flushing the ground down the sewer line.

Can you provide pictures or give other details as far as recent work done or if you have a basement or if you have trees in the area?

If it is a water service break it could be more serious. If it is just settling around a recently installed gas line then it is not serious and a plumber coming out will just bill you for something he can't do anything about.
posted by JJ86 at 8:17 AM on January 10

BTW a sewer line collapse can wait until Monday providing you don't use the sink or toilet or shower or anything else which may cause a backup. Typical sewer line collapses will be seen as a sewage backup in your house before you see a depression in your front lawn.
posted by JJ86 at 8:20 AM on January 10

leahwrenn writes "This will not be cheap: we had a 3'x'5'x4' hole appear in our yard and brought a couple of plumbers in to see if they thought it was water-line or sewer-line related, and we were quoted between $200 and $500 to run the camera."

Some places the local athourity will do this for free. EG: the city of Calgary will scope your line for free if you are having a problem to determine whether you have a blockage.
posted by Mitheral at 8:57 AM on January 10

We had our sewer line replaced around this time last year. In our case the symptoms were that during heavy load on the sewer (showers, toilets, draining the washing machines all at the same time) water would rise precariously in the basement floor drains and occasionally rise above just a little bit.

The plumbing people scoped our line for free for the diagnosis. A lot of our line had started to collapsed from our house to the street. Our line was made out of what looked like terracotta pipe and was original to the house (built in the late '30s). They said that stuff was only designed to last 50 years so it did its duty. The new pipe is plastic and is rated for 70-80 years.

As for installation, cost is going to vary greatly depending on how long your run is and how deep the run is. Apparently ours was exceptionally deep. Expect a backhoe to rip up your yard and start budgeting time to re-seed/re-sod the length of your run come spring. The ground also might settle some over time leaving a bit of a dip. The contractor should give you some advice on how to minimize that. You may have to add some dirt to your yard before adding seed.
posted by mmascolino at 9:58 AM on January 10

thanks for all of your help! I love askmefi.

I ended up shutting off water to the house, left town for the weekend, and had a glorious time.

I dug out my inspection report, which said that the sewer line was PVC. Talked to a neighbor, who said there was digging ~3 years ago.

3 yrs seemed like a long time for settling, but there was a *lot* of rain the week before it settled. Called a plumber, and they thought it was conceivable to have settling 3 yrs out.

I want to replace the water intake line anyway, so I asked for them to scope the sewer in exchange for giving them the job to replace the water in line, and they agreed. They scoped the sewer, and it's just fine.

thanks again for your help!
posted by comah at 11:26 PM on February 10