What is the process for installing French drains with a sump pump?

For a wet basement, we install an interior French drain by cutting a channel in the floor at the floor wall joint, laying perforated pipe in stone, and routing every drop to a sump pump that lifts the water out and away from the house. That whole system, our Forever Dry System, runs $3,000 to $30,000 and it is guaranteed to be dry for life!

Here is how the work actually goes.

We start with a free inspection. We find where the water gets in and why. Most of the time the soil right against your foundation is disturbed backfill, the looser dirt that got put back when the house was built. It drains slow. It holds water. NH frost heave makes it worse by pushing on the walls.

Then we lay out the drain. We cut a channel in the concrete floor along the inside of the footing, right at the floor wall joint where most basement water sneaks in. The trench follows the full perimeter, or just the wet walls if that is all you need.

Next comes the pipe. We set perforated drain pipe in a bed of clean stone inside that channel. The stone lets water find the pipe fast. The pipe carries it to one low point.

That low point is your sump. We dig a pit, drop in a sump basin, and seat the pump. We size it at 1/2 hp per 120 feet of drain, so a bigger basement gets more pump. The pump kicks on when water rises and pushes it out a discharge line, away from the foundation.

We patch the concrete back over the drain. Clean finish. Then we add the rest of the system: a 12-mil vapor barrier on the walls and a dehumidifier to handle the damp air. That combination is what keeps a basement dry, not just one piece of it.

A few things drive the cost. How many walls are wet. How long the drain run is. Whether you need one sump or two. Whether we add a battery backup. The full Forever Dry System price lands at $3,000 to $30,000, and we give you that quote within 24 hours of the inspection.

One thing we will tell you plainly. You may not need the whole perimeter. If only one wall leaks, we drain one wall. We are not going to sell you pipe you do not need.

We back the sump pump system for 3 years (batteries are not included), and the dehumidifier for 5. The Forever Dry System itself carries a full transferable lifetime warranty. See the 603 guarantee for the fine print.

A quick word on the outside-dig version. Some crews want to excavate around your house and waterproof the exterior wall. In our field experience that fix tends to fail in about two to three years once the soil settles back. Interior drainage is the durable fix, and it does not tear up your yard.

If you want a backup, we use a battery sump. A charged backup battery can pump about a residential pool’s worth of water during an outage, roughly 15,000 to 20,000 gallons [verify], which buys you time when the power and the storm hit together.

Learn more on our basement waterproofing page. Crawl space instead of a basement? That is a different system, see crawl space services. If your trouble is a leaning or cracked wall, start at structural and foundation repair.

The Insurance Information Institute notes that most standard homeowner policies do not cover groundwater seepage, which is one more reason to fix the source (iii.org).

Ready when you are. Call us at 603-610-1770 or book your free inspection and we will tell you what your basement actually needs.

Related questions

Do I need a French drain on every wall? No. If only one wall leaks, we drain that wall. We size the system to the water you actually have, then quote it within 24 hours.

French drain or exterior waterproofing, which lasts? Interior drainage. In our experience the outside-dig fix tends to fail in two to three years as the backfill settles, and it tears up your yard. Interior pipe and a sump keep working.

Do I need a backup sump pump? If your power goes out in storms, yes. We use a battery backup. A charged battery can move about a pool’s worth of water, roughly 15,000 to 20,000 gallons, before it needs power again.

How big a sump pump do I need? We size it at 1/2 hp per 120 feet of drain. A bigger basement, or two wet zones, may call for a second pump. We figure that on the free inspection.