How long does a sewer line last?

The honest answer is that a sewer line does not have a service life the way a roof does. It has a material, an installation, and a set of ground conditions, and those three things together decide when — or whether — it becomes a problem.

That is not a dodge. It is the reason a house from the 1920s can have a perfectly serviceable lateral while one from the 1950s needs replacing, and it is the reason “your line is due” is not a diagnosis.

Below are the service lives we work to, quoted exactly as they are written in our own material reference. Every one of them carries a qualifier, and the qualifier is the important half of the sentence.

Sewer laterals

Vitrified clay:

often still structurally sound at a hundred years, provided the joints have held — age alone is not a reason to replace clay

Cast iron:

commonly quoted at fifty to a hundred years, but corrosion rate depends heavily on what has been running through it

Orangeburg:

frequently reaching end of life within thirty to fifty years, and any that remains in service is well past the age it was designed for

Concrete:

typically long-lived, though crown degradation can run well ahead of the pipe’s apparent age where ventilation has been poor

ABS:

expected to outlast most of the houses it was installed under, absent physical damage

PVC:

expected to outlast most of the houses it was installed under, absent physical damage

Water services

Copper:

commonly decades of service, with soil conditions along the run mattering more than age

Galvanized steel:

commonly quoted at several decades, though flow is usually unacceptable well before the pipe actually leaks

Lead:

structurally long-lived, which is precisely the problem: it does not fail in a way that forces its own replacement

And what goes back in

HDPE:

specified for a service life measured in generations rather than decades, which is the reason bursting is worth doing at all

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Now read the qualifiers

Every one of those sentences has a clause attached, and the clauses are not hedging for its own sake. Each one names the variable that actually decides the outcome.

Clay: “provided the joints have held”

The clay is inert. It does not corrode, it is chemically indifferent to everything a house sends down a drain, and it does not get tired. What has a service life is the joint — and clay is laid in short lengths, so there is one every few feet for the whole run.

So the question is never how old the clay is. It is what has been happening at the seams, which is a question about ground movement and about what is growing above the line. Put a mature elm over a jointed clay lateral and the joints have been under attack for decades. Put the same pipe under a lawn with nothing on it and it can still be fine.

A replacement quoted off the age of the house is a quote against the calendar. Ask for the footage.

Cast iron: “depends heavily on what has been running through it”

Cast iron does not fail from the outside in. It corrodes from the inside, and the rate is set by chemistry rather than by years. Two identical lines installed the same week can be in completely different condition.

There is a second trap here. Cast iron fails through the bottom of the pipe, where the flow sits, while the crown still looks fine. The pipe can appear intact from above and be gone underneath — which means a survey that is not specifically looking for channelling along the invert can produce a reassuring answer about a line that is nearly finished.

Orangeburg: “well past the age it was designed for”

The only material on the list where age genuinely is the story, because it was never intended to last as long as the house. It deforms before it breaks: oval under soil load, then delaminating from the inside, then collapsed.

It is also the only one where the finding closes the decision — it cannot be lined, so there is no lining conversation to have.

Concrete: “where ventilation has been poor”

Concrete is attacked from the top down by sanitary gas, not from the bottom up by flow. The crown degrades while the submerged invert stays sound, and how fast that happens depends on conditions inside the pipe rather than on the date it was laid.

Plastic: “absent physical damage”

Three words doing an enormous amount of work.

ABS and PVC do not have a wear-out mechanism in ordinary service. They do not corrode, they do not scale, and they have very few joints. What ends a plastic line is an event: a belly where the bedding settled, a crushed section where something heavy went over a shallow run, one gasketed joint that was not seated properly on the day.

So on a plastic line the useful question is not “how old is it” but “what happened to it”. Usually the answer is nothing, and a blockage in a sound plastic line is a cleaning rather than a replacement. In the newer half of this city that is the common case and it is worth insisting on the footage before accepting anything else.

Lead: “does not fail in a way that forces its own replacement”

The one entry on the list where long service life is the problem rather than the reassurance. A lead service can remain watertight indefinitely. That is exactly why it has to be identified deliberately rather than waited out — how to work out what you have.

What actually shortens a line

If you want a list of things that matter more than the year on the deed:

• What is growing above it. A mature broadleaf root system over jointed pipe is the single most common structural cause of sewer trouble in the older parts of Calgary.
• How it was bedded. A belly is an installation defect that shows up decades later. The pipe never failed; the ground under it settled.
• What has been put down it. Grease, in particular, and anything fibrous that should have gone in a bin.
• What has driven over it. A shallow run under a spot where a truck parked during a renovation is a real failure mode with a date attached.
• How many times it has been cabled. Every pass takes a little of the wall on a line that is already deteriorating.
• Ground movement. Freeze and thaw, settlement, load from above. It is what offsets joints.

What nobody can tell you

How many years you have left. Not from the age of the house, not from the material alone, and not from footage either.

A camera survey shows you a condition on a day: what the pipe is, whether it still holds its shape, where the defects are and how many. That is enough to decide what to do now. It is not a forecast, and anyone offering one is inventing it.

What a survey does give you is a baseline. A line that has been surveyed once can be surveyed again in a few years and compared, and two data points tell you something one never can — whether it is stable or moving. On a line with known defects and no urgency, that is frequently the right thing to buy instead of a repair.

The short version

Clay can be sound at a century. Plastic will likely outlast the house. Cast iron depends on what has gone through it. Orangeburg is finished and was always going to be. Concrete depends on what happened above the flow line.

None of which tells you about your line. That is what the camera is for, and it is why we do not quote without one.

What the camera shows · The three common materials compared · Book a survey