The longer answer
What each one actually does:
- Exterior French drain / buried downspouts: intercept surface and shallow groundwater before it loads up the clay around your basement. Water that never reaches the foundation never has to be pumped. Typical cost: $300–$700 per downspout burial, $1,500–$3,800 for a yard French drain.
- Sump pump + interior drain tile: collects water from under the slab into a pit and pumps it out. Essential in homes with high water tables or finished basements — but it runs on electricity, wears out, and does nothing to stop the water from arriving.
The honest decision framework for KC homes:
- Basement gets damp only after hard rain? Start outside. Fix downspouts and grading first — it's the cheapest fix and very often the whole answer on KC clay.
- Water table is genuinely high, or water appears even in dry weather? You need the sump system — and exterior drainage still reduces how often it runs.
- Finished basement you can't afford to gamble on? Do both: exterior interception plus a sump with battery backup. The pump becomes insurance instead of the only defense.
The trap we see constantly: the self-defeating sump pump. The pump ejects water through a short discharge pipe that dumps right beside the foundation. On KC clay that water soaks straight back down, re-enters the pit, and the pump runs again — the same gallons on a loop, wearing the pump out years early. If your sump kicks on every few minutes during wet weeks, look at where the discharge goes first. Burying the discharge line to a pop-up emitter 5–30 feet out runs $300–$700 and breaks the cycle.
Watch out for one-tool salesmen. Basement waterproofing companies sell interior systems ($8,000–$15,000); landscapers sell drains. We install exterior drainage and replace sump pumps ($1,500–$2,800 cast-iron), so we'll tell you which combination your water problem actually calls for — free walk, written quote. Start here: French drains & drainage or French drain vs foundation repair.