Laying sewer pipes seems easy until you discover that water drains but odours remain, the washing machine siphons a floor trap, and the toilet “thinks” before it flushes. In sewer work, the geometry matters as much as the pipe itself: run length, slope, bends, venting and maintenance access.
Which pipes and diameters are used
- 40–50 mm — sinks, shower, bathtub, washing machine.
- 75 mm — sometimes for a combined branch serving several fixtures.
- 100–110 mm — toilet, riser and main outlet.
- Materials — most often PP/PVC, with HDPE or silent systems for specific cases.
What matters most during laying
- Correct fall. Around 2% is a common target for domestic gravity lines.
- Fewer sharp bends. Two 45° fittings are usually better than one 90° elbow.
- Correct tees and entries. Branches should join with the direction of flow, not against it.
- Clean-outs. Long or complex sections need camera and rodding access.
- Noise control. Near bedrooms and living rooms, silent pipe or acoustic wrapping is often worth it.
Where new sewer lines are usually routed
- Inside the screed. The standard scenario in a major renovation.
- Inside a service shaft. For vertical sections and lines that need access.
- Along a wall in a boxing. When the floor cannot be raised or the slab cannot be touched.
- Outside in the yard. When the line runs to a manhole, septic or external main.
What it costs
- Short internal branch — 600–1,800 ILS
- Bathroom rough-in for renovation — 1,500–4,500 ILS
- Main run from bathroom to riser — 2,000–6,000 ILS
- Chasing, floor opening and finish restoration — priced separately on top
Frequently asked
Can the pipe be laid with almost no fall if it is new and smooth?
No. Even a smooth new pipe must work as a gravity line with proper fall. Otherwise water leaves first and solids remain inside the line.
Why are 90-degree turns undesirable?
At a hard 90° turn the flow slows down, sediment settles faster, and both a cable and a camera pass through with more difficulty. That is why smoother routing is preferred.
Should a clean-out be installed from the start?
If the run is long, concealed or has several bends — yes, absolutely. A clean-out is cheap insurance against having to open a wall or floor later.