Drainage & Earthworks
Weeping Tile Calculator
Calculates perforated weeping-tile pipe and gravel for a foundation perimeter drain
Updated June 26, 2026 · Live
What this tool does
Calculates the length of perforated weeping-tile pipe and the volume of drainage gravel for a foundation perimeter drain, from the footing perimeter and trench size.
Formula Used
Spotted something off?
Calculations or display — let us know.
People also use
How the weeping tile calculator works
This calculator takes the footing perimeter, adds 5% for corners and cleanouts to size the perforated pipe, and multiplies perimeter × trench width × gravel depth to size the clear-stone bed that surrounds it. Weeping tile is a perimeter drain that follows the foundation footing — not a field drain spread across an area.
What weeping tile does
Weeping tile (perforated drain pipe) is laid alongside the footing, holes down, in a bed of clear stone wrapped in filter cloth. It collects ground water before it can build hydrostatic pressure against the foundation and carries it to a sump pit or to daylight. It is one of the most important parts of a dry basement in a Canadian climate.
Pipe, gravel and filter cloth
Residential weeping tile is usually 100 mm (4") perforated pipe. Surround it with washed clear stone — not sand or fines, which clog the perforations — and wrap the stone in a non-woven filter fabric so soil cannot migrate in. Keep a consistent slope toward the sump or outlet.
What this tool does not do
It estimates pipe and gravel quantity only. It does not design the drainage system, size the sump pump, set the slope, or assess an existing wet basement — those are the work of a foundation or drainage contractor and, where the footing is disturbed, may need an engineer.
Adjusting the defaults
Every input is editable. Enter your own perimeter, trench size and pipe diameter and the pipe length, gravel and cost recalculate instantly. All BuildMetricLab tools run in your browser — no sign-up, no data sent anywhere, and every formula is shown so you can audit the math.
On-site considerations
Lay the pipe below the top of the footing so it drains the critical zone, and never above it. Bring a cleanout riser to grade at one or two corners so the line can be flushed later. Tie the system to a sump with a reliable pump and a battery or water-powered backup — a perimeter drain only protects the basement if the water it collects actually leaves.
Using this alongside other BuildMetricLab tools
Pair this with the French drain, gravel/aggregate and excavation volume calculators when planning foundation drainage, and with the material cost calculator to price the pipe, stone and fabric.
Sources & methodology
Calculates the perforated pipe as the footing perimeter plus 5% for corners and cleanouts, and the drainage gravel as perimeter × trench width × gravel depth. Every result is calculated from the values you enter, and all inputs are editable.
Frequently asked questions
Are weeping tile calculator results accurate enough to order materials?
Use them as a starting estimate only. Verifying the final quantity with your supplier or contractor before ordering is good practice — site conditions, wastage and cut-offs all affect the true figure.
What wastage percentage should I use?
The calculator defaults to the typical Canadian trade allowance for drainage & earthworks. Increase it for complex cuts, awkward shapes, or first-time DIY. The default wastage allowance reflects common trade practice; values lower than the default may underestimate offcuts.
Does this replace professional advice?
No. This tool is a planning estimator. For works that affect structure, the National Building Code (NBC), property-line or shared-wall, gas, electrics, drainage to a sewer, or similar, consult a suitably qualified professional.
Can I change the unit prices?
Yes — every price field is editable. Plug in your supplier's quote to get a total that matches your project.
Related tools
Calculators from other categories that planners often reach for next.