Downspout Underground Drain Cost Calculator
Estimate the cost to bury your downspout drain lines from the number of downspouts, the run length each one needs and your price per linear foot.
Calculator
4 downspouts extended 20 ft each at $12.00/ft is about $960.00. Carrying roof water underground and away keeps it off the foundation.
Roof water is one of the biggest and most avoidable causes of a wet foundation. A downspout that dumps rain at the base of the wall sends a huge volume of water straight into the soil against the footing; carrying that water underground in a buried pipe and releasing it several feet away — at a pop-up emitter, a daylight outlet on a slope, or a dry well — keeps it off the foundation entirely. This calculator prices that job from three simple numbers: how many downspouts you are burying, how far each one has to run, and your installed price per foot.
The math is deliberately plain — downspouts × run × $/ft — and, as everywhere on the site, the price per foot is one you supply from a real quote. That is what makes the estimate durable: the arithmetic never changes and the price is always current because it is yours.
Formula
Total buried pipe is the number of downspouts times the run each one needs, priced by the foot:
Total = downspouts × run length (ft) × your $/linear ft
Use an average run length across your downspouts, or run the tool per downspout if the distances differ a lot. The price per foot is the installed figure from your quote — it covers trenching, the buried pipe, fittings, back-fill and the outlet.
Worked example
Say you want to carry 4 downspouts underground, each needing about a 20 ft run to a pop-up emitter, at a quoted $12 per buried foot:
- Total pipe → 4 × 20 = 80 linear ft
- Total → 4 × 20 × $12 = $960
Fewer downspouts, shorter runs or a lower per-foot price bring it down; longer runs to a distant daylight outlet push it up in direct proportion.
Background & practice
Burying downspout lines is shallow trenching in the yard, not excavation against the foundation, so it carries the standard planning-estimate note. It is also one of the highest-value, lowest-cost improvements you can make to keep a basement dry — often worth doing before more expensive interior or exterior waterproofing.
What the per-foot price covers
An installed foot of buried downspout drain usually bundles the trench, the pipe (solid rather than perforated, since you want to carry water, not let it seep out), the fittings that connect to the downspout, back-fill and the outlet fitting. Ask whether the quote includes the pop-up emitter or a dry well at the end, since those can be separate.
Runs, outlets and slope
Each line needs a continuous downhill run to its outlet so it drains and does not hold standing water. Aim to release the water well away from the house — a common rule of thumb is at least several feet beyond the foundation, farther on flat lots. If your downspouts sit at very different distances from a usable outlet, run the tool once per downspout and add the results, rather than averaging, for a tighter estimate.
Pair it with the rest of the drainage plan
Downspout lines often feed into, or run alongside, a broader surface-drainage plan and catch basins. If roof water is only part of the problem, price the yard drainage too; if subsurface water is pushing against the foundation, that is where a French drain and a sump come in. The related calculators cover each piece so you can build up the whole picture.
Frequently asked questions
How much does it cost to bury downspout drain lines?
Multiply downspouts × run length × your price per foot. Four downspouts at 20 ft each and $12/ft is 4 × 20 × $12 = $960 in the worked example. Enter your own runs and quoted per-foot price for your number.
How far should downspout drains discharge from the house?
Release the water well away from the foundation — a common rule of thumb is at least several feet beyond the wall, and farther on flat lots — at a pop-up emitter, daylight outlet or dry well. The run length you enter should reach that outlet.
Should downspout drain pipe be solid or perforated?
Solid pipe — you want to carry roof water to a distant outlet, not let it seep out along the way next to the house. Perforated pipe is for French drains, which are designed to collect water, not transport it.
My downspouts are different distances from the outlet — how do I estimate?
Run the calculator once per downspout with each run length and add the totals, rather than using a single average, for a tighter estimate. Or use the average run for a quick ballpark.
Is burying downspouts worth it?
Often it is one of the cheapest, highest-value drainage fixes: moving roof water away from the foundation can meaningfully reduce basement moisture before you spend on interior or exterior waterproofing.