What Are Drainage Works and What Do They Cost? A Plain Guide

Drainage works is a broad term for any job on the pipes that carry waste and rainwater away from a property: clearing blockages, surveying, repairing damaged pipes, laying new drains and connecting to the public sewer. The cost depends far more on which of those you actually need than on the phrase itself, so the first step is working out which kind of drainage work your problem calls for. Clearance and survey work are priced on our published rate card by job type and time band; repair and new work are quoted per job, because depth, length and access change from one property to the next.

What counts as drainage works?

Drainage works falls into five groups: maintenance and clearance, inspection, repair without digging, repair or replacement by excavation, and new installation. Each has a different price structure, and a quote should say which one it is for.

Maintenance and clearance covers unblocking, rodding and high-pressure jetting. Inspection means a CCTV survey, drain tracing or testing, which tells you what is wrong before anyone commits to a repair. Our guide to how much drain tracing costs covers what sets the price of a trace. No-dig repair fixes a pipe from the inside with a liner or patch. Excavation means digging down to replace a broken, collapsed or badly displaced section. New installation covers new drain runs, inspection chambers, soakaways and connections, usually for an extension, a new bathroom or a change of layout.

When a company quotes for "drainage works" without saying which of these it means, ask. The difference between a clearance and an excavation can be the difference between a short visit and several days on site.

What does clearance and maintenance work cost?

Clearance is the cheapest and most predictable drainage work, because the job is well defined. The price is set mainly by the time band you book in, where the blockage is and what it is made of.

A blockage reachable from an inspection chamber or gully and cleared with rods or a jetter is a standard job. The price rises when the blockage is compacted fat or wipes, when the run is long, or when access means working through a neighbour's chamber or a basement. Scheduled maintenance, such as regular jetting of a restaurant drain, is priced per visit and is cheaper per visit than calling out for each blockage, because the engineer is not clearing a full obstruction every time.

Why should inspection come before repair?

Because no one can price a drain repair honestly without seeing inside the pipe. A CCTV survey turns a guess into a quote, and it costs far less than digging up the wrong section.

A survey records the condition of the pipe, the position and depth of each defect and the distance from the access point. That is what a repair quote should be built on. If a company offers to dig or reline based only on symptoms, you are paying for their guess. Our CCTV drain survey is priced as a fixed fee with the footage and report included, and the survey is itemised separately from any repair, so you are free to get a second repair quote using the same report.

What sets the price of drain repairs?

Repair costs are driven by depth, length of damage, what is on top of the pipe and whether the pipe can be lined or must be dug up. The pipe material itself is rarely the biggest factor.

A shallow clay pipe under a lawn is a much smaller excavation than the same pipe a metre and a half down under a driveway, a patio or a kitchen extension. Reinstating the surface afterwards, whether that is block paving, tarmac or tiles, is often a large part of the bill and should be itemised. Relining avoids most of that when the pipe is still round and in line, but it cannot fix a fully collapsed section or a pipe that has sunk out of level. Our guide to no-dig repair versus excavation explains which defects suit each approach.

What does new drainage work involve, and what needs permission?

New drainage is the most variable kind of drainage work, because it depends on the design, the ground and the approvals needed. Most new work falls under Building Regulations, and some needs consent from Thames Water or the council as well.

New or altered drains are covered by Part H of the Building Regulations, so the work is normally inspected by building control or an approved inspector. If you plan to build over, or within 3 metres of, a public sewer, Thames Water's approval is needed before building starts. A new connection to the public sewer needs the sewerage company's consent too, and any digging in the road or pavement needs a permit from the highway authority. Each of these adds time and fees that sit outside the contractor's own price, so a good quote lists them separately instead of rolling them into one figure.

Groundworks for new drains are priced on length, depth, the number of chambers and the reinstatement needed. A short run from a new bathroom to an existing chamber is a modest job. A new connection across a front garden and under the pavement is a much larger one.

Who pays for drainage works?

You pay for drains that serve only your property and sit inside your boundary. Pipes shared with neighbours, or running beyond your boundary to the sewer, are usually the water company's responsibility.

Since October 2011, most shared private sewers and lateral drains in England and Wales were transferred to the sewerage companies, which in London mostly means Thames Water. In a leasehold building, shared drains are usually the freeholder's responsibility and are paid for through the service charge. Checking ownership before booking can save you paying for work that is not yours. Our guide on who pays for a blocked drain in London sets out a simple test.

How do you compare quotes for drainage works?

Compare the scope, not the total. Two quotes for "drainage works" can describe completely different jobs, so ask each company to list what it will do, in what order and at what price.

A comparable quote names the type of work, the length and depth involved, how many access points or chambers, whether a survey is included or already done, what surface reinstatement is included, and which permits or approvals are extra. If one quote is much cheaper, look for what it leaves out: reinstatement, waste removal and building control fees are the usual gaps. If you are not sure which kind of drainage work you need, describe the symptoms and we will tell you whether it starts with a clearance, a survey or a repair quote.