Plumbing, septic tank and drainage layout basics
Plumbing is cheapest and most reliable when wet areas are planned together at the start. Bathrooms and the kitchen stacked in the same place on every floor keep pipes short.
Group wet areas
Put bathrooms back to back or one above another. They can then share a vertical drainage stack. Fewer stacks mean fewer penetrations through slabs and less cost.
Waste and water lines
- Waste (soil and drain) pipes: usually 3 to 4 in PVC, sloped continuously towards the stack. Avoid sharp bends.
- Water supply pipes: smaller, pressure-rated pipes (CPVC or PPR) from the overhead tank to taps, showers and the kitchen.
- Vent pipes: keep the drainage system breathing so water traps do not empty.
Septic tank and soak pit
Where there is no sewer line, waste flows to a septic tank and then to a soak pit. The tank is sized by the number of users and the desilting interval, and it needs a safe distance from any drinking water source such as a tube well. Tank location also needs space for a vehicle or workers to reach the manhole for cleaning.
Overhead water tank
Place the tank on the roof, over a column or wall line that can carry its weight when full, and close to the water risers. Plan a pump and overflow pipe.
Draw it first
The PlanCraft 3D planner has a plumbing layer. Place inlet points, waste outlets, drainage stacks, septic tank, soak pit and the overhead tank, then use the pipe tool to join them. Water pipes appear in blue and drains in brown, and the cost estimate counts the pipe length you drew.
Tank sizes, pipe diameters and distances are set by local regulation and a plumbing designer. Use this guide for planning only.
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