Drain Survey Found Problems When Buying a House: What Next?

If a drain survey finds problems when you are buying a house, you have four realistic options before you exchange contracts: ask the seller to repair, negotiate the price down by the cost of the repair, agree a retention held back from the sale money, or walk away. Which one makes sense depends on how serious the defect is, who owns the pipe, and what a repair actually costs, so get those three answers before you negotiate.

First, work out how serious the defect really is

Not every finding in a survey report is a problem worth negotiating over. The structural and service grades in the report tell you whether you are looking at a failing pipe or a pipe that needs cleaning.

A structural grade of 4 or 5 means the pipe itself is badly damaged or failing: fractures, broken sections, deformation or collapse. That needs a repair, and it is a fair basis for negotiation. A structural grade of 3 usually means deterioration that should be planned for rather than fixed tomorrow. A high service grade with a low structural grade means the pipe is sound but obstructed by grease, scale, silt or roots, and the answer is cleaning, which costs far less than a repair.

Minor cracks, slight joint displacement and light deposits are normal in a London drain that is eighty or a hundred years old. If the report shows only grade 1 and 2 observations, it is telling you the drains are typical for the age of the house. Our guide to reading a CCTV drain survey report explains the grades and the defect codes line by line.

Check who owns the damaged pipe

Before you ask the seller for anything, find out whether the defect is in a private drain or in a public sewer. If it is the water company's pipe, it is the water company's repair, and it should not come off the price of the house.

As a general rule, a pipe that serves only your property and sits within its boundary is a private drain and belongs to the owner. Since October 2011, most pipes that serve more than one property, and the sections of a single property's drain that run outside its boundary, have been the responsibility of the water company, which in most of London is Thames Water. A defect in a shared run behind a terrace, or under the pavement, may well be theirs.

The survey report should show the defect on a plan with a distance from the nearest chamber, so the boundary question can be answered. If the plan is vague, ask the surveyor to confirm where the defect sits relative to the property line before anyone negotiates. The drainage and water search your conveyancer ordered will also show whether a public sewer runs within the boundary.

Get a costed repair quote, not a guess

A price reduction is only as strong as the figure behind it. Ask for a written repair quote that references the survey, the run and the position of each defect, and states the method.

The method matters because it changes the cost a great deal. A single fracture in an otherwise sound pipe may be fixed with a short patch liner from inside. A long run with several fractures may need full-length lining. A collapsed or badly deformed pipe usually has to be dug up. Our drain relining page explains when lining is the right repair and when the pipe has to be excavated instead.

Be wary of a quote that proposes relining every run when the report shows service defects only. Cleaning a pipe that is sound costs a fraction of lining it, and a seller's solicitor who sees an inflated quote will push back.

Your four options before exchange

Everything is negotiable until contracts are exchanged. After exchange you are committed to buy, so any renegotiation, repair or retention has to be agreed and written into the contract before that point.

• Ask the seller to repair before completion. This works for a clearly defined job, but you have less control over who does it and how. If you choose this route, ask for a post-repair CCTV survey showing the repaired section, not just an invoice.
• Reduce the price. The cleanest option for a significant defect. You arrange the repair yourself after completion with a contractor you have chosen. Tell your lender if the price changes, as your conveyancer will explain.
• Agree a retention. Part of the purchase money is held by the solicitors until the repair is done, then released to the seller. Useful when the seller wants to do the work but you want a safeguard.
• Walk away. Reasonable if the defect is severe, the repair would involve digging under an extension, or the seller will not engage.

A retention needs the solicitors on both sides to agree the wording, so raise it early rather than a day before exchange.

Why your insurance will not pay for it later

A defect you knew about before you bought is a pre-existing defect. Home insurance policies generally exclude damage that existed before the policy started and damage caused by gradual deterioration, so you cannot rely on a claim to cover it after completion.

This is the main reason to deal with the finding during the purchase rather than after. If a problem only appears later, the survey you commissioned before buying becomes useful evidence of the pipe's condition at that point, because insurers look closely at whether damage was sudden or gradual.

When a drain problem should not change the deal

Sometimes the honest answer is that the finding does not justify renegotiating. A grease build-up, a few root fibres at a joint or a missing chamber cover are maintenance items, not reasons to reopen a price.

It is also worth separating drainage findings from paperwork problems. An extension built over a public sewer without the water company's consent is a legal and conveyancing question rather than a repair, and it is dealt with differently, as our guide to build over agreements and CCTV surveys explains. If you are still deciding whether a survey is worth commissioning at all, start with should you get a drain survey when buying a house.