Every fall on the Island, the same conversation starts. First atmospheric river hits, and a homeowner notices water pooling against the foundation, a damp smell in the crawlspace, or a sump pump that suddenly won’t stop cycling. The perimeter drain around the base of the house has failed — or it’s about to.
Perimeter drains are the black perforated pipe that runs around your foundation, buried a few feet down, collecting water from roof drainage and grade runoff and carrying it away from the house. When they work, you never think about them. When they fail, water goes into the foundation instead of past it.
Here’s when the drain actually needs to be dug up and replaced, when it can be flushed and left alone, and how to tell which situation you’re in before someone quotes you a big number.
How a perimeter drain fails
Three failure modes, in rough order of how common they are on the Island:
Silt and sediment buildup. Over 20–30 years, silt washes into the drain pipe from the surrounding soil and gradually reduces the flow area. Not a catastrophic failure — the drain still works, just slower. You notice this after a heavy rain event when water takes longer to drain away than it used to.
Root intrusion. Cedar and Douglas fir roots find perforated drain pipe irresistible. They grow through the holes, then keep growing. A drain that was fine for 25 years can start choking off in year 26 as a root mass fills a section. Common on properties with mature landscaping close to the foundation.
Pipe collapse. Older drain systems on the Island used clay tile or thin PVC that fails structurally over time. A section collapses, the drain stops draining past that point, water starts building up upstream. This is the failure mode where flushing won’t help — the pipe is physically gone.
Two other patterns worth knowing:
- Improper original install. Older Nanaimo and Sooke homes sometimes have drains that were never quite installed to code — insufficient slope, missing filter fabric, no proper daylight discharge point. These fail young and predictably.
- Downspout dumping directly into the perimeter drain. Big fall rain event overloads the drain because the roof water was supposed to go somewhere separate. Not a drain failure per se, but a diagnosis to know before we recommend digging.
When to flush vs. when to dig
Flush candidate — signs point to silt or partial root intrusion, drain is still passing SOME water, no evidence of collapse:
- Cycle time on the sump pump has increased over years but the pump still keeps up
- Water pools briefly after heavy rain but clears within a day or two
- Damp crawlspace but no active water intrusion
- Drain camera scope shows a partially blocked pipe with the pipe structure intact
A proper flush (high-pressure jetting) can restore meaningful flow for several years on this pattern. Cheaper than digging. Buys you time.
Dig candidate — signs point to collapse, major root damage, or original-install failure:
- Water backing up into a crawlspace or basement during rain
- Sump pump running continuously and can’t keep up
- Camera scope shows a collapsed section, missing pipe, or a root mass that jetting won’t clear
- Water pooling against the foundation for days
- Cracks or heaving in the foundation wall that suggests hydrostatic pressure
If you’re in the dig category, no amount of flushing will fix it. The pipe has to come out and a new one has to go in.
What “we dig perimeter drains” actually means
Our sister plumbing brand, Under The Seat Plumbing (UTS), digs perimeter drains. It’s a real service we perform in-house, not something we sub out to a third party. Here’s what a full perimeter drain replacement looks like on an Island home:
- Excavation around the foundation to expose the existing drain. This is the biggest cost driver — access, machinery, landscape restoration.
- Old drain removal. The failed pipe comes out. On older homes this can also be the moment you find the original waterproofing is compromised and needs attention.
- New pipe install. Modern rigid PVC with filter fabric, proper slope, correct discharge point. Sized to the roof area feeding it.
- Foundation waterproofing check. If we’re already down there, we look at the foundation wall condition. Sometimes a drain replacement is also the right window for adding a dimple board or membrane on the outside.
- Backfill with proper drain rock, not just native soil. This part matters — cheap backfill is why some new drains fail as fast as the ones they replaced.
- Landscape restoration. Grade back to shed water away from the house. Reseed or replant what was disturbed.
Cost depends heavily on excavation access — a home with clear side yards is one job; a home with landscaping, decks, or a driveway over the drain line is another. This is why we don’t quote perimeter drain work over the phone. Every property is different.
When to have someone look
Symptoms that mean call this month, not next spring:
- Water actively pooling against your foundation after a rain
- Damp or musty smell in a crawlspace that wasn’t there last year
- Sump pump running noticeably more than in previous winters
- Any visible water intrusion in a basement or crawlspace
- Downspouts backing up (may indicate downstream drain blockage)
Symptoms that can wait until spring for a scope:
- Drain that’s slower than it used to be but still passes water
- Damp in the crawlspace that’s stable year over year
- Drain that hasn’t been scoped in 15+ years and you’re just being proactive
What to expect from us
A plumber from Under The Seat Plumbing (UTS) — our sister plumbing brand — comes to your home, walks the exterior grade, checks any accessible cleanouts, and (where warranted) runs a camera scope through the perimeter drain to see the actual pipe condition. Written quote for whatever’s needed — flush, partial repair, or full excavation and replacement.
Family-owned. Island-grown. 4.9 ★ Google Rated across the Island. Note that Sasquatch’s 1-year workmanship guarantee is specific to heat pump installs; drain work is quoted with its own terms.
Call (236) 361-8293 to get on the schedule, or reach us through our contact page.
— The Sasquatch Field Team
