The best pipe for a sewer line replacement, and what the labels mean

01 /What is the best sewer pipe to use for a replacement?

The best pipe is the one approved for the use, matched to the installation method, and installed on a firm, well-compacted bed. For most Canadian house laterals replaced by open cut, that means PVC sewer pipe with gasketed bell-and-spigot joints. Where the line is burst, it means HDPE fused into one continuous length. Where the line is relined, the liner is the new pipe and the old one stays.

Vitrified clay and concrete are still used for large municipal sewers, but they are seldom chosen to replace a house lateral today. If you find either in a quote for a residential lateral, ask why.

02 /What does SDR 35 mean, and is SDR 28 better?

The rating is a standard dimension ratio (SDR), found by dividing a pipe's outside diameter by its wall thickness. SDR 35 means the wall is one thirty-fifth of the diameter; SDR 28 has a thicker wall for the same diameter, so it is stiffer and resists deflection under soil load better.

Is SDR 28 better? It is stiffer, and on a deep line or under a driveway that margin is worth having. But flexible plastic pipe gets most of its strength from the soil around it. A PVC pipe is designed to deflect slightly and push against well-compacted material at its sides. Put SDR 28 on a lumpy trench bottom with loose backfill and it can still sag; put SDR 35 on proper bedding with compacted haunches and it will perform as designed. Ask what the contractor proposes and why, and check whether your municipality specifies a minimum for the portion it regulates.

In Canada, PVC sewer pipe is certified to CSA Group's B182-series standards, and 100 mm residential sewer pipe is commonly stocked as SDR 28 or SDR 35. The ASTM standard for PSM-type PVC sewer pipe, D3034, is also widely referenced. Look for the certification marking printed along the pipe.

03 /When is HDPE the right replacement pipe?

HDPE is the right pipe when the new line is being pulled in rather than laid in a trench, which in residential work mostly means pipe bursting. It is supplied in long lengths or coils, heat-fused into a single string with no gasketed joints, and flexible enough to bend into a launch pit without cracking.

• Jointless: butt-fused joints leave no gasket for roots to find.
• Tough: it tolerates the scraping and point loads of being pulled through fractured pipe fragments.
• Dimension ratio (DR): like SDR, lower means thicker. Ask what DR is proposed and whether it suits the depth.
• Transitions: HDPE cannot be solvent-welded, so each end joins PVC, ABS or cast iron with an approved mechanical coupling or fitting.
• Locating: HDPE is not magnetic, so a tracer wire or marker is needed if you want to find it with a standard locator later.

For the bursting process itself, see pipe bursting explained.

04 /What about ABS and PVC drain-waste-vent pipe under the house?

Inside the house and under the basement slab, the building drain is usually replaced with ABS or PVC drain-waste-vent (DWV) pipe with solvent-welded joints. Both are common in Canadian homes; ABS is especially familiar in many western Canadian houses. The choice often comes down to what the rest of the house uses and what the local inspector accepts.

1. Match the system. Joining ABS to PVC needs an approved transition method, usually a mechanical coupling, rather than a mixed solvent joint.
2. Keep solvent welding warm and clean. Cold, damp conditions slow cement cure; follow the product's temperature guidance.
3. Test before cover. New drainage piping is normally tested for leaks before the slab is poured back, when the inspector requires it.
4. Think about the backwater valve. A slab replacement is the easiest time to add one where the municipality recommends or requires it.

Replacing a sewer line under a basement slab walks through that job step by step.

05 /Which size of pipe should the replacement be?

Most single-family laterals in Canada are 100 mm (4 in), and a like-for-like replacement is usually right. Larger houses, multi-unit buildings and some older homes use 125 or 150 mm. Upsizing is sensible when fixture load, a new suite, or local standards call for it, not simply because bigger sounds safer.

Oversizing has a cost beyond price. A gravity sewer relies on flow velocity to carry solids along. In a bigger pipe, the same household flow spreads out into a shallower, slower stream, which can leave more solids behind on flat grades. That is why sizing and slope are set together, and why the plumbing code, not preference, governs them. If a contractor proposes a change in size, ask what the code or the municipality requires and how the slope will be set.

06 /What details separate a good replacement from an average one?

The pipe is the smallest part of the specification. The details around it decide whether the line drains well for decades and can be found, cleaned and inspected when it needs to be.

07 /Does the replacement material affect how long the line lasts?

Yes, but installation quality usually matters more. Modern plastics do not corrode, and fused or gasketed joints resist roots far better than old mortar or packed joints. Industry groups quote design lives measured in many decades for PVC and HDPE sewer pipe. The failures seen in plastic lines are almost always installation or ground problems: sags from poor bedding, joints that were not fully seated, or damage from later digging.

For lifespans of both the old and new materials, see how long sewer pipes last. To see which methods, and therefore which pipes, fit your site, try the Replacement Method Selector, then request quotes that state the pipe, rating and bedding in writing.

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