07-Aug
The other day, I was doing some digging at the side of my house, and
found something that I have no clue what it is or what it is for.
I was digging near the area where the sewer pipe exits the house. I
always assumed that the lateral is just a simple sloped pipe that heads
out to the municipal street sewer. However, after the lateral exits the
house for a few feet, it inlets into a little dry-well type structure
that is about 2 ft in diameter and covered with a round stone slab.
Then, there is an outlet on the other side of the dry-well that acts as
the continuation of the lateral. The house is about a hundred years
old, and so this must have been part of the old sewer system, but I'm
not sure what the purpose of that well-structure is.
Any ideas? I have some ideas on what it might be but I don't want to
answer my own questions and just have people repeat it back to me. I
want to hear what a professional plumber would say or someone else
knowledgeable on the subject would say.
Thanks for any help provided.
--Jim



From:
I worked with plumbing for quite a few years before I retired. I did
not do all that much underground work but I worked on a few sewer
lines. I never saw anything like what you describe. Every one I ever
saw was just a pipe going to the street which was normally clay on
older houses. The only thing I can think of, would be a grease trap.
However, those were normally only on septic systems. Of course, there
probably was a septic 100 years ago, so what you have might be a
manhole of sorts where they converted the old pipes from the septic to
the city sewer. Then too, assuming you are at your foundation level,
which means at least 6 feet deep, there would be little sense in
having a grease trap that deep.

It would be much easier to ID if you posted a photo. Got any way to
do this?
Also, tell us this......
How deep it it?
What material is it made from?
What state and / or country are you in?
What material is the lateral made from?
If you lift the rock, can you see sewerage flowing, or is this thing
unused?
Are there additional pipe inlet /outlets, such as where rain gutter
drops could have entered?
Is this "rock" a plain field rock or a cement casting?
Is there gravel around it?
Are there any drain tiles nearby?
Are there "drops" (pipes) under your downspouts?
If yes, where do they go?
Why are you digging anyhow?
*** Is is filled with money? lol
Mark



From: Speedy Jim
It used to be common practice (still is in some places)
to provide a "house trap" on the lateral leaving the bldg.
It could also be a "backwater valve" to prevent sewage backing
up into the house; kind of a check valve.
Jim



Aug. 07
How deep it it?
total depth from ground level (the lid is a few inches underground) to
bottom is about 4 feet. There is the cover, then the well goes down 2
ft, then there is the inlet hole for the lateral on one side and the
outlet hole for the lateral on the other side, and then the well
continues down another 2 ft.

What material is it made from?
Clay... shape-wise, it's very similar to those plastic buckets that
basement
sump-pumps sit in. It has a bottom, the a clay wall about 4 ft tall, 2
ft diameter, and then it flanges wider at the top.

What state and / or country are you in?
Southeast Michigan

What material is the lateral made from?
Clay

If you lift the rock, can you see sewerage flowing, or is this thing
unused?
It is being used... the bottom 2 ft (as previously described) is filled

with sludge, and the top 2 ft is clear... I imagine this is a direct
result of the design, since the inlet and outlet pipes are at the
mid-point.

Are there additional pipe inlet /outlets, such as where rain gutter
drops could have entered?
No... I saw on a website that some old city houses and buildings had a
drywell for rainwater from the gutters to flow into and dissipate
through holes (kind of like a seepage pit used further out from some
modern septic tanks)... but there is no connection to collect any such
water... there is only the inlet which is the sewer pipe coming out of
the basement, and the outlet which I'm pretty sure goes to the street
sewer.

Is this "rock" a plain field rock or a cement casting?
The cover? It looks like a limestone slab... 2 ft diameter, 3 inch
thick. It's round and covers the clay-well, but it's not a great
seal... I think a previous homeowner brought it in when an older cover
was perhaps broken.

Is there gravel around it?
Some driveway gravel, but not a special gravel section to suggest
drainage if there were holes in the well.

Are there any drain tiles nearby?
None known.

Are there "drops" (pipes) under your downspouts?
If yes, where do they go?
Nope... I covered part of this answer a few questions back.


Why are you digging anyhow?
I need a good bed of limestone in the driveway before paving on top of
it.

*** Is is filled with money? lol
There might be a Lincoldn Wheat Cent or two at the bottom of the
sludge.



From:
OK, I get a much better picture now.
That seems like an awfully shallow sewer pipe for the cold winters of
Michigan. Being that shallow tells me that it originally went to a
septic. Modern sewer pipes are generally below the basement floor and
go deeper outside.
I would say that it's most likely a sediment separator and/or grease
trap. They did things quite differently in the old days. Grease
traps were used to keep heavy grease out of the septic, which tends to
clog with greases.
In many ways, it sounds real handy, because if your sewer backs up,
you can access it for cleaning easily, and if the sewer system backs
up, you can prevent the house from filling with sewerage by opening
that thing. Plus if you flush your wedding ring down the toilet, you
know where to find it (yuck).
On the downside, if no one knew it exists, the poor plumber that would
try to run a rotary auger from the house to the street, would be
really frustrated when the auger kept stopping at that point.
I would highly recommend that you DO NOT pave over it. Make yourself a
nice concrete cover or buy one. In the future there WILL come a time
you'll need to get in there. I hope this is not being driven over.
Walking is fine.
It might be interesting what sort of objects are in the bottom of that
sludge....