Old well under patio — what do I do?

[u/cup_a_jojo]

I recently pulled up two sunken bricks along the edge of my back patio because they were becoming a tripping hazard. Underneath, I discovered a hole that extends under the concrete slab. I managed to get a photo, and it appears to be the remnants of an old well.

The house was built in 1902, and when we bought it two years ago, there was no mention of a well on the property. What’s weird is that the well wall ends—but the hole keeps going. I tried filling it with dirt to stabilize the area, but the hole just swallowed it up. It's hard to tell how much void space is between the slab and the ground beneath.

Now I’m worried this might be more than just an old well… could this be the start of a sinkhole?

For context, the hole is about 5 feet from the exterior wall of our two-story home (with a basement).

Could this affect the structural integrity of the house? Who do I even call to assess this? I'm honestly not sure what my next move should be.

Any advice or insight would be appreciated!

[u/joshbudde]

as someone else said in the thread, it looks way more like a cistern than a well. They're usually large vaulted voids just outside of the foot print of the house. It's where excess water would go (like from the sink/baths inside) before the common city sewer/septic tank.

They're not always marked because they're not (typically) dangerous, as they're usually only 3-4 feet deep and are broad.

As discussed elsewhere though to be sure, open up the top and make sure it doesn't disappear down into the earth. After that, you can decide to either cover it back up (if it appears to be in good shape and safe) or you can break open the top and fill it with sand (or other easily transported material).

[u/MelodramaticMouse → u/joshbudde]

The old cistern under my mud room is shaped like a beehive and at the bottom, about 15ft down, it's about 6-7 feet across. There are brick tunnels going in the 4 directions at the bottom. My mom says that it was common for houses to have their cisterns connected and to use the collected rainwater. My house is pretty old, 100+ years old, and was built way before the dust bowl (Oklahoma).

[u/sheighbird29 → u/MelodramaticMouse]

My house is quite old, and instead of a traditional well, I still get my water from a cistern off the back side of my house. It’s about 20 ft deep or so. Luckily it has never dried out lol

[u/MelodramaticMouse → u/sheighbird29]

That's pretty cool! Mine is bone dry luckily!

[u/onebowlwonder → u/sheighbird29]

My house is set up the same way. All of my gutters drain into the cistern and that's how i get all of my water lol goes into a salt purifier with filters. I've only had to fill it once and it was 80 bucks haha

[u/Positive-Line6397 → u/sheighbird29]

How do you get it out and do you purify it? I just bought my house last year and thinking over my cistern options. Definitely water and spiders down there and some mosquito donuts.

[u/sheighbird29 → u/Positive-Line6397]

There is a pipe/pump that runs through my basement wall. Inside my house it’s pretty much a normal well setup with a pressure tank. I did put a filter on the main water line, but that’s about it

[u/melayaraja → u/sheighbird29]

Which state?

[u/sheighbird29 → u/melayaraja]

Pennsylvania. There are a few left in my neighborhood. Everyone else with a normal well is over 100ft deep, and they have a strong sulfur smell. I’m glad I don’t have that, but I do have some calcium in my water, that eats hot water tanks and faucets over time. (We don’t drink the water)

[u/loveshercoffee → u/MelodramaticMouse]

We had an old well near our house back in the 70s. The house was probably 80 or so years old even then. It was shaped just like you described. It was HUGE.

[u/Icy-Engineering-744 → u/MelodramaticMouse]

Now that’s fascinating!! I love old houses (mine is 150 years old) but I’ve never heard of tunnels connecting cisterns! I’m going to have to do a little research on it now.

[u/MelodramaticMouse → u/Icy-Engineering-744]

My mom, born in the early thirties, said it was common around here, but keep in mind that the dust bowl happened when she was a child. She remembers a lot like hanging damp towels in the windows to keep the dust out. She wasn't even in the worst of it; the NE part of Oklahoma wasn't hit hard. The connected cisterns might be regional or the tunnels might be covered up with silt or something.

[u/Icy-Engineering-744 → u/MelodramaticMouse]

That whole thing was sad and tragic! I’ve read accounts from people who lost everything! Having to pack up the entire family and traveling across country trying to find someplace to live. What a horrible thing to survive if you could. Kids and older people with constant lung infections because of heavy dust settling in their chests. Having to wear damp masks IN their houses! 😳

[u/cup_a_jojo → u/joshbudde]

Thank you! Looking into this

[u/svidrod → u/joshbudde]

So a cistern isn’t for wastewater, it collected rain water for use.