French Drain vs Sump Pump: Which Fixes a Wet Basement
A sump pump ($300 to $800 installed) removes water that collects in a pit; a French drain ($4,000 to $17,000 for an interior basement system) collects water from around the perimeter and delivers it to the pump. They are not alternatives; an interior French drain system includes a sump pump by design. A pump alone without a collection system only helps if water already flows to the pit on its own.
Homeowners with wet basements often ask whether they need a French drain or just a sump pump, as if the two compete. They do not. A sump pump is one component; a French drain is the system that feeds it. This guide explains what each does, what each costs, and the combinations that actually keep basements dry.
What a sump pump does (and does not) do
A sump pump sits in a pit (the sump basin) at the lowest point of the basement and pumps out water that reaches it. A pedestal or submersible pump, a float switch, and a discharge pipe to the outside: installed cost $300 to $800 for the pump and basin, $500 to $1,000 more for a battery backup. What a pump cannot do is gather water. If water seeps through a wall crack ten feet from the pit, a lone pump does nothing for it; the water has no path to the pit. A pump without a collection system only works when water naturally flows to the pit location, which is rare.
What a French drain adds
An interior French drain is the collection system: perforated pipe in gravel around the inside perimeter of the foundation, under the slab edge, pitched to drain into the sump pit. It gives water from anywhere along the walls a path to the pump. The installed system runs $4,000 to $17,000 including the pump, basin, and concrete restoration. Exterior French drains do the same job from outside, intercepting water before it reaches the walls, at $30 to $90 per foot to footing depth.
The combinations, ranked
Best: interior French drain plus sump pump with battery backup. This is the professional standard for a chronically wet basement: collection around the full perimeter, powered ejection, and backup when storms kill the power (which is when you need it most). Good: exterior French drain to daylight. No pump needed if the lot slopes; water flows out by gravity. Ideal for new construction or accessible lots. Adequate: sump pump alone. Works when the water problem is minor and localized near the pit, for example a high water table that seeps up in one corner. Inadequate: neither, or a pump in a pit with no collection. The most common disappointment: a homeowner installs a $500 pump, the basement still leaks at the far wall, and the pump sits in a dry pit while water pools elsewhere.
Battery backup: the part people skip
Basements flood during storms, and storms cause outages. A sump pump without backup is a fair-weather system. Battery backups ($500 to $1,000 installed) run the pump for hours on a deep-cycle battery; water-powered backups use municipal water pressure and run indefinitely but consume water and are banned in some areas. If your basement has ever taken water during a storm with a power flicker, the backup is not optional.
What about waterproof paint and sealants?
Drylok-style waterproof coatings ($30 to $50 per gallon) manage minor dampness and efflorescence on walls, but they do not stop hydrostatic pressure: water under pressure will push through or around them. They are a fine supplement to a drainage system, not a substitute. Similarly, exterior waterproof membranes are excellent when the foundation is already exposed during construction, but applying them to an existing home means excavating, which is the expensive part anyway.
The bottom line
Do not choose between a French drain and a sump pump; the drain collects and the pump ejects, and an interior system needs both. Budget $4,000 to $17,000 for the full interior system with pump, add the battery backup, and fix grading and gutters first: the cheapest water to pump is the water you kept away from the house.
Figures current as of October 2026. Sources: HomeGuide and Angi 2026 cost data, contractor-published pricing guides.