TryBuildCalc

French Drain / Land Drain Materials Calculator Verification Checklist

Essential Checklist+

Complete these critical checks before approving the work or proceeding to the next construction stage.

✓17 Inspection Points
✓5 Verification Categories
✓Survey, Outlet & Utilities+
  • A real outlet has been identified, and it is lower than the deep end of the trench
  • Buried services located and marked before any digging
  • The source of the water is understood, not assumed
✓Setting Out the Fall+
  • The fall set at 1% or steeper, and checked along the whole run, not just end to end
  • The depth at the OUTLET end calculated and confirmed as achievable
✓The Trench & Geotextile+
  • Trench width leaves stone all round the pipe, not just above it
  • Geotextile specified, and it is non-woven filter fabric rather than woven weed membrane
  • The fabric wraps the stone completely, with the flaps folded over and overlapped
  • Trench stability assessed, and anything over 4-5 ft deep properly supported
✓Pipe & Stone Envelope+
  • Pipe laid with the perforations facing DOWN
  • Clean, washed, angular open-graded stone — not pea gravel and not crusher run
  • At least 2-3 in of bedding stone placed and levelled before the pipe goes in
  • At least 3 in of stone over the crown of the pipe before any cap goes on
  • The run from the stone to the outlet is SOLID pipe, not perforated
✓Outlet, Finishing & Testing+
  • The outlet is protected against rodents, blockage and being mown over
  • The drain flow-tested with a hose before the trench is closed
  • If the drain is capped with soil, surface water has a deliberate way in
Full QC Checklist+

Verify where the water is coming from and where it is going, setting out the fall, the trench and its geotextile, the pipe and stone envelope, and the outlet, testing and aftercare.

✓26 Inspection Points
✓5 Verification Categories
✓Survey, Outlet & Utilities+
  • A real outlet has been identified, and it is lower than the deep end of the trench
  • Buried services located and marked before any digging
  • The source of the water is understood, not assumed
  • The contributing area measured, including roof and hard surfaces that discharge to it
  • Permissions and discharge restrictions checked
✓Setting Out the Fall+
  • The fall set at 1% or steeper, and checked along the whole run, not just end to end
  • The depth at the OUTLET end calculated and confirmed as achievable
  • Whether the ground already falls has been established, not assumed
✓The Trench & Geotextile+
  • Trench width leaves stone all round the pipe, not just above it
  • Geotextile specified, and it is non-woven filter fabric rather than woven weed membrane
  • The fabric wraps the stone completely, with the flaps folded over and overlapped
  • The fabric roll is wide enough for the wrapped section, or the seams are planned
  • Trench stability assessed, and anything over 4-5 ft deep properly supported
  • Spoil disposal planned on the bulked volume, not the trench volume
✓Pipe & Stone Envelope+
  • Pipe laid with the perforations facing DOWN
  • Clean, washed, angular open-graded stone — not pea gravel and not crusher run
  • At least 2-3 in of bedding stone placed and levelled before the pipe goes in
  • At least 3 in of stone over the crown of the pipe before any cap goes on
  • The run from the stone to the outlet is SOLID pipe, not perforated
  • Grade re-checked across every coupling and along the pipe after backfilling stone
  • Filter sock use decided deliberately, not by default
✓Outlet, Finishing & Testing+
  • The outlet is protected against rodents, blockage and being mown over
  • The drain flow-tested with a hose before the trench is closed
  • If the drain is capped with soil, surface water has a deliberate way in
  • The line of the drain recorded before it disappears
  • A maintenance expectation set — a French drain is not fit-and-forget
Inspection Notes+
Use the latest approved drawings, specifications, and site measurements.
Complete all critical checks before proceeding to the next work stage.
Record deviations and confirm rectification where required.

Related Calculators & Guides

French Drain / Land Drain Materials Calculator CalculatorOpen the related calculator and verify the current project inputs.

FAQ

Use it after collecting the project inputs and again before approving or closing the relevant work stage.
No. It supports verification but does not replace approved drawings, specifications, codes, manufacturer requirements, or professional inspection.