What drives the size of a sewer project

Two contractors can quote the same length of pipe and arrive at numbers that do not look like they belong to the same job. Usually they do not: one has priced reaching the pipe and putting everything back, and the other has priced the pipe.

This page does not tell you what anything costs. SewerOwner publishes no prices and cannot — they depend on your ground, your property, and your local requirements. What it does is name the factors, so you can see which of them each proposal has accounted for.

What this page cannot establish

SewerOwner cannot tell you what is wrong with your line, and nothing on this page is a diagnosis
the words a contractor uses have no agreed definitions in this trade, and two companies use them differently
no price, range, or cost driver on this site is a quotation, and none can be
nothing here establishes who is responsible for the length of pipe being described
SewerOwner publishes no prices, ranges, or estimates and cannot indicate what any work should cost
SewerOwner cannot establish the depth, route, or ground conditions at your property
nothing here indicates that any quote is high or low

The factors that move the number

Ask which of these each proposal has accounted for. A factor that is not mentioned has either been assumed away or will arrive later as a variation.

Depth: The single largest driver in most excavated work. Depth changes the volume of ground moved, the support the excavation needs, and how long the machine is on site. It is also frequently estimated rather than established.
Pipe material and condition: What is being removed or worked around. Material affects whether a no-dig method is available at all, which changes the shape of the whole job.
Access: Whether machinery can reach the route. A back garden reachable only through a house is a different job from a front garden with a driveway beside it, at any depth.
Landscaping: What is above the line and what putting it back means. Mature planting, established lawn, and irrigation all cost more to reinstate than bare ground.
Driveways and paving: Breaking out and reinstating a hard surface is its own trade with its own cost, and the standard it is put back to should be written down rather than discussed.
Sidewalk and street: Work in a public surface usually brings approvals, notice periods, traffic requirements, and a reinstatement standard set by somebody other than you. Whether the work reaches that far changes the project category.
Other utilities: Gas, water, electricity, and telecoms crossing the route require locating and careful working. A conflict found mid-job stops the job.
Groundwater: Water in the excavation means pumping, means the sides need more support, and means the work is slower. It is rarely known before the ground is opened.
Roots and trees: A mature tree over the route affects the method, the excavation, and sometimes what may lawfully be removed.
Approvals: What has to be permitted, who obtains it, how long it takes, and what has to be inspected before the trench is closed.
The connection at the far end: Whether the work reaches the point where the line meets the wider system, and whether anybody has actually seen that point.

The comparison that actually works

Put the proposals side by side and ask, for each factor above, what each one says. Where one is silent, that is not necessarily an omission — it may be included and unstated, or excluded and unstated. Either way it is a question with a short answer.

A cheaper proposal is sometimes cheaper because it covers less. That may be exactly right for your situation. It becomes a problem only when nobody has said so.

What to ask about any quote

What depth have you assumed, and how did you establish it?
What is included for putting surfaces back, and to what standard?
What have you assumed about other utilities on the route?
What happens to the price if the ground is wetter than expected?
Which approvals does this need, who obtains them, and is that in the price?
Does the scope reach the connection at the far end?
What is the process if something is found that changes the work?

What would change the answer

the approximate depth of the line and how that was established
the route across the property and what it crosses
what each proposal states about restoration of disturbed surfaces
what approvals the work needs and who obtains them

What to do next

The difference between two numbers is almost always a difference in scope, and scope is comparable in a way that price is not.

Lay the proposals out by what each states it covers

If your situation is different

You have only one quote so far: Reading a sewer proposal
You want to know what is excluded: Exclusions and assumptions
Work has been scheduled already: Preparing for replacement

Project timeline
The same factors that drive scope drive how long it takes.
Trees and roots
A tree over the route changes the work and sometimes the method.
Preparing for lining
The no-dig route, and what it does and does not avoid.
Restoration
Putting the surface back is frequently the largest under-specified item.
Permits and inspections
Approvals change the sequence and sometimes the standard of work.
Change orders
What happens to the price when the ground turns out differently.
Get help
A person reads it. It is not a contractor booking, and describing what you were told is often enough to work out which question is actually unanswered.