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–$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–$9,800 typical.
- Combined interior + exterior — for homes with both surface runoff and rising groundwater. $9,400–$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"–18" wide, 18"–24" deep, lined with filter fabric
- 3" gravel base below the perforated pipe
- 6" perforated pipe (PVC or HDPE), slope 1/8"–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–$6,400
- Interior french + sump basin + pump + battery backup — $7,200–$9,400
- Combined interior + exterior drainage — $9,800–$12,200
- Bundled with full encapsulation (typical) — package pricing usually $1,200–$2,400 less than separate scopes
Common questions
How long does a sump pump last?
Primary pump: 7–10 years of normal duty. Battery backup unit: replace battery every 4–5 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.