Eight Questions to Ask Before You Hire a Drainage Contractor
Most drainage money gets spent twice — once on a system built wrong, and again on the system that fixes it. The decisions that determine which one you get are all made before anyone digs, and most of them are visible in the conversation.
Here is what to ask, and one thing to do first that costs nothing.
Before you call anyone, go stand in the rain
Film the water while it is moving. This is the single most useful thing you can do, and it is free.
Phone video during active rain is the highest-value diagnostic input there is. A dry-day site visit is guesswork about where water went. Thirty seconds of footage is evidence.
What to capture
Every downspout while it is actually discharging. Not the downspout. The discharge.
The spot that holds water, filmed from far enough back that the slope around it is visible. A tight shot of a puddle tells no one anything.
Where water crosses a driveway or walk — the crossing points are where velocity and volume become obvious.
Where it enters your property from a neighbouring yard, if it does. This matters legally as well as technically.
The same low spot again about two hours after the rain stops. How fast it clears matters as much as how deep it got.
Nobody can tell you what a puddle does from a photograph of a puddle. The video answers questions a contractor would otherwise have to guess at — and guessing is what gets priced into the quote.
There is a printable shot list for this: How to Film Your Drainage Problem, six shots with what each one is for and how to read the footage afterwards.
The eight questions
1. Where exactly does this water discharge, and is that point on my property?
If a contractor cannot walk over and point at it, you do not yet have a plan. Routing your standing water twenty feet sideways onto the neighbouring lot is not a solution, it is a transfer, and North Carolina courts have addressed it — under the reasonable use rule from Pendergrast v. Aiken (1977) a landowner may alter drainage on their own land, but not in a way that dumps a new burden on a neighbour.
NC licensing standards require French drains to terminate to daylight or existing storm drainage, and require dry wells and cisterns to have an overflow outlet.
2. Is the pipe carrying my downspouts solid or perforated?
The only correct answer is solid. Perforated pipe collects water moving through soil; solid pipe carries water that is already gathered. Put roof water into perforated pipe and you saturate the exact soil the system was installed to dry out, then silt the system shut over a season or two. We wrote this up in full in Perforated or Solid?
3. What fabric is going in — woven or non-woven needle-punched?
Non-woven needle-punched for anything intercepting seepage. Woven fabric is engineered for strength under load, not for letting water through, and behind stone on a seepage application it builds pressure instead of draining. The two look nearly identical in a roll and cost about the same, which is why a lot of installers do not distinguish. The answer to this question tells you a great deal about who you have hired.
4. Why this pipe diameter? What is the catchment and the available slope?
Four-inch is the default. Six-inch needs a reason: several lines combining into one main, catchment above roughly 1,200 square feet on a single run, available slope under 1 percent, or a main running off 9-inch or 12-inch basins. Upsizing without one of those inflates the price and, on a line with limited fall, can run worse. To be safe is not an engineering reason, and you are paying for it by the foot.
5. Is restoration — sod, seed, mulch — a line item, or an afterthought?
Trenching leaves a scar across the yard. Whether it gets put back properly is a scope question, and it is much easier to settle before the machine arrives than after.
6. Who called NC811, and when?
Three working days' notice, filed in the state where you are digging. Union County sits close enough to the South Carolina line that this genuinely matters — file in the state the shovel is actually in.
Photograph every paint mark and every flag before work starts, time-stamped. If a line is cut later, those photographs are the only thing that establishes what was marked and what was not.
7. Does this scope cross into anything requiring a professional engineer?
This is the line we would rather state plainly than quietly step over. A licensed landscaping and drainage contractor can assess observed conditions and recommend and install a remedy. A professional engineer is required for:
Retaining walls over five feet of unbalanced fill. The North Carolina residential threshold moved from four feet to five effective January 2025 — confirm local variation, since some jurisdictions differ.
Any wall crossing a property line, or supporting a structure, at any height
Public-catchment sizing
Stormwater control measure design and as-built certification
If a contractor quotes a six-foot retaining wall with no engineer involved, that is not a bargain. That is unpermitted structural work on your deed. There is more detail in When Does a Retaining Wall Need an Engineer in North Carolina?
8. If you are repairing someone else's work, what is and is not warranted?
Tying new pipe into an existing system means inheriting whatever is already buried. A contractor who will say out loud which parts they stand behind and which they do not is being straight with you.
A contractor who answers all eight without hesitating is worth more than one who is $400 cheaper.
One more thing before you buy materials
Do not lime until the soil results come back. Your pH may already be fine. North Carolina residents can have soil tested through NCDA and CS, and the boxes are free outside the December to March peak window, when a $5 per-sample fee applies. Boxes come from any Cooperative Extension county center.
Lime and starter fertilizer bought ahead of the test are frequently money spent on a problem you did not have.
The full guide
The printable Water Where You Don't Want It: A Piedmont Drainage Guide carries this question list along with the pipe and geotextile specifications, the discharge legality section, riprap and stair details, and the market cost ranges for drainage work in this area so you can tell a real number from a guess.
If you would rather someone just looked at it
We do on-site property assessments in Union County and the surrounding Piedmont: a walkthrough, measurements, aerial photography, and a written scope of what is actually happening with the water on your property.
The assessment fee is credited toward the work if you decide to hire us. If the answer is that you do not need us, we will tell you that too. You can request a consultation here.
Alex Purdy, Carolina Terrain, Waxhaw, North Carolina. NC Landscape Contractor License CL.1872, NCSU Stormwater SCM Inspection and Maintenance Certification #5970, NDS Certified Drainage Contractor. Educational guidance only. This is not a design, not an engineered or stamped plan, not a boundary survey, not utility locating, and not a site-specific recommendation for your property. I am a licensed contractor, not a professional engineer and not a registered landscape architect.
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