Ontario · Paperwork · 2026
How to draw a septic cross-section the examiner accepts
The cross-section is the drawing owners fear most — and the one examiners bounce most. It is not art. It is a vertical slice through your bed showing seven specific things. Miss one and the package comes back.
What it is: a side view through the leaching bed, from finished grade down past the limiting layer, with every depth and thickness labelled. It proves on paper that the Code’s vertical clearances actually exist on your lot.
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The part nobody tells you
Designers charge $800–$2,000 just for the paperwork in these quotes.
Ontario law lets you do that part yourself, on your own property. OntarioSepticDesigner.ca turns your answers into the same 26-page package the township clerk sees every day — calculations, drawings, forms, all of it.
The seven things the drawing must show
1Finished grade — the surface line after backfill, with slope direction
2Distribution pipe — depth below grade, bedded in stone
3Stone layer — thickness above and below the pipe, labelled
4Filter fabric — the line between stone and backfill
5Native soil or imported sand — what the bed sits in, with the sand depth if raised
6The limiting layer — bedrock, high water table, or impermeable soil, at its measured depth
7The clearance dimension — the unsaturated distance between the bottom of the bed and the limiting layer, drawn and labelled
The number the whole drawing exists to prove
Everything on the cross-section serves one question: is there enough unsaturated soil — 900 mm for a conventional bed — between the bottom of your stone and the highest point of the water table, bedrock, or impermeable layer? That figure comes from your test holes — the drawing just presents the evidence. If your lot cannot deliver it in the ground, the bed comes up: that is what a raised bed is, and the cross-section is where the examiner sees the imported sand doing that job.
Why cross-sections bounce
Four reasons, over and over: no limiting-layer line at all; depths that contradict the test-hole log elsewhere in the package; stone thickness missing or below Code; and unlabelled drawings the examiner cannot verify. Every one is a resubmission — weeks lost to a labelling problem.
Drawing it by hand: perfectly legal, honestly tedious
Townships accept hand drawings. Use graph paper, pick a vertical scale (1 square = 100 mm works), draw the slice, and label every layer with real measured numbers. Two rules keep you safe: every number on the drawing must match the same number everywhere else in your package, and nothing gets drawn that was not measured. Budget an evening, plus a redo when you find a mismatch.
The $18,950 line that never appears on a quote
A real worked example: 3-bedroom bungalow, conventional bed. Tank supplied and set, pipe, stone, fabric, one day of machine and labour, permit allowance — $13,049 with HST. The same job quoted at $32,000. The gap is design fees, markup, and labour you may not need to buy.
Two minutes on the free checker shows the numbers your own lot generates — daily flow, tank size, risk level — before anyone quotes you.
Or let the software draw it from your numbers
The Permit Package Builder generates the cross-section automatically from the same inputs that drive your calculations — bed depth, stone spec, sand depth, water-table reading. The numbers cannot contradict the worksheets because they come from the same place. The generated drawing and the site-plan overlay are included in every paid plan, not an upgrade. See a finished one in the sample package.
Cross-section questions, answered straight
Does the cross-section need to be to scale?
It needs a stated scale and accurate labelled dimensions. Clean graph-paper work with a scale note is accepted everywhere.
Can I trace an example drawing?
You can copy the format — never the numbers. The depths must be your lot’s measured values, and the examiner will check them against your test-hole data.
Do I need a cross-section for a tank-only replacement?
Usually not — if the bed is untouched, most authorities want the site plan and tank details only. Ask your local office before drawing one for nothing.
What scale should I use?
Anything readable and stated. 1:50 vertical is common; on graph paper, one square per 100 mm keeps arithmetic easy.
The drawing that draws itself
Enter your measurements once. The builder produces the cross-section, the site plan and every worksheet from the same numbers — nothing to contradict. $99.99.