Interior basement drain systems
If water shows up along the bottom of your basement walls, an interior drain is the most common fix. Here's how it works.
An interior drain system, sometimes called an interior French drain or drain tile, is a perforated pipe laid in a trench around the inside edge of the basement floor, next to the footing. Water that seeps through the cove joint or the lower wall drops into the pipe and runs to a sump pit, where a pump lifts it out of the house. It doesn't stop water from reaching the foundation. It gives that water a controlled path out instead of across your floor.
When does an interior drain make sense?
- A puddle or wet line where the wall meets the floor after heavy rain
- Water coming up through the joint between the slab and the wall
- Seepage on more than one wall, which points to groundwater rather than one bad crack
- A stone or block foundation where sealing the whole wall from inside isn't realistic
How is it installed?
- Cut the slab. The crew saws and breaks out a strip of concrete along the affected walls.
- Dig the trench. The trench runs beside the footing, sloped toward the sump location.
- Lay pipe and stone. Perforated pipe goes in a bed of washed stone, often wrapped in filter fabric to keep silt out.
- Add a wall channel or membrane. On block walls, weep holes or a dimple membrane lets water inside the cores drain down into the system.
- Patch the floor. New concrete goes back over the trench, usually leaving a narrow gap at the wall so water can still reach the pipe.
What should I ask before hiring?
- Which walls will get drain pipe, and why those walls?
- Where will the sump go, and where will the pump discharge outside?
- Are there cleanouts so the pipe can be flushed later?
- What does the warranty cover, and is it transferable if you sell?
- What's the PA registration number, and will it be on the contract?
What affects the price?
- How many linear feet of wall need drain pipe
- Slab thickness and how much finished space has to be moved or removed
- Wall type: block cores and stone foundations need different treatment
- Whether a new sump pit and pump are part of the job
The waterproofing company sets the price, and it should do that only after someone has been in the basement, looked at the walls, floor joint and sump, and walked the outside of the house. We don't quote prices. A figure offered over the phone before anyone has seen the foundation is a rough guess, not a quote.
Where we connect you with help
Common questions
Does an interior drain stop water from getting into the wall?
No. It catches water that has already come through the wall or floor joint and carries it to the sump. If you need water kept out of the wall itself, ask about exterior waterproofing.
Can I finish my basement after an interior drain is installed?
Many homeowners do. Ask the company how to frame walls so the drain and wall channel stay accessible, and keep the sump lid reachable.
Related services
More background: Lycoming County basement water guide.
Wet floor after every storm, or a sump that runs all night?
Call and a Lycoming County waterproofing company will set up a visit.