Which drainage solution is right
Three configurations, picked based on existing grade, soil, and water source:
- Exterior perimeter french drain to daylight, cheapest, longest-lasting when grade allows. 6" perforated pipe in a gravel-wrapped trench, sloped to daylight outflow. $4,900 to $7,800 typical.
- Interior perimeter french drain to sump basin + pump, for homes where exterior daylight discharge isn't possible (urban lots, flat sites, hardpan). $6,400 to $9,800 typical.
- Combined interior + exterior, for homes with both surface runoff and rising groundwater. $9,400 to $12,200 typical.
The right pick depends on a site visit. Network specialists run a quick percolation test on suspect soils before quoting.
What the install actually involves
- Trench 12" to 18" wide, 18" to 24" deep, lined with filter fabric
- 3" gravel base below the perforated pipe
- 6" perforated pipe (PVC or HDPE), slope 1/8" to 1/4" per foot
- Gravel backfill above and around pipe to within 4" of grade
- Filter fabric wrap-over, then native soil and topsoil restoration
- Sump basin (interior systems): 18"×24" or 22"×30" pre-cast or polymer, set in gravel
- Sump pump: 1/3 HP minimum for crawl-space discharge, primary + battery backup, on dedicated circuit
- Discharge line: rigid PVC, sloped, terminating at least 10 ft from foundation, with a check valve
The battery backup on the sump pump is not optional. Heavy rain events in Northern California often coincide with power outages, exactly when you need the pump most. Every network specialist includes battery backup as standard.
What you'll spend in 2026
- Exterior french drain to daylight, 80 lin ft, sloped lot, $4,900 to $6,400
- Interior french + sump basin + pump + battery backup, $7,200 to $9,400
- Combined interior + exterior drainage, $9,800 to $12,200
- Bundled with full encapsulation (typical), package pricing usually $1,200 to $2,400 less than separate scopes
Common questions
How long does a sump pump last?
Primary pump: 7 to 10 years of normal duty. Battery backup unit: replace battery every 4 to 5 years, unit lasts 10+ years. Total system service life ~15 years before any major replacement.
Will my landscaping survive the trench?
The trench is restored at finish, topsoil, then native plantings or sod. New plantings need a season to establish. Larger trees within 6 ft of the trench may need root pruning; the specialist flags this at the inspection.
Can I just add a sump pump without french drain?
For very specific cases (single isolated wet corner with a known source), yes. For most situations, no, the sump can only pump out water that reaches it. The french drain is what gets the water TO the sump.