Guides · Harrow

What Drain Unblocking Costs and What Changes the Price

Drainage is a trade where the same job can be quoted at wildly different prices, and where the final bill sometimes bears little relation to the figure given on the phone. This page explains what actually determines the cost of clearing a blocked drain in Harrow, so you can judge a quote properly and avoid the two or three ways this goes wrong for people.

The method dictates the price

Rodding is the cheapest approach and works on soft, localised blockages within reach of an accessible chamber - most blocked toilets and many kitchen waste blockages fall into this category. High-pressure water jetting costs more because it needs a jetting unit and a trained operator, but it is what clears compacted fat, scale, root growth and blockages further down a run, and it cleans the pipe wall rather than just punching a hole through the obstruction. A CCTV survey adds cost again and is used where the cause is not obvious or where the blockage keeps returning. A quote that seems unusually low is often a rodding-only price for a job that will need jetting.

Access, and why the first question is always about chambers

How quickly a blockage is reached is the biggest variable in labour time. A property with an accessible inspection chamber in the front garden is a straightforward job. A property where the chambers are behind a locked side gate, under a decked area, beneath a patio or inside a garage takes considerably longer, and in some cases needs lifting equipment. In much of Harrow - particularly around Pinner, Stanmore and Harrow Weald where properties have long side returns and mature gardens - chambers are commonly behind side gates or under later extensions. Knowing where yours are before you call, and clearing access to them, genuinely reduces what you pay.

Time of day and the emergency premium

Out-of-hours and weekend rates are higher, and that is legitimate. What is worth understanding is when the premium is worth paying. If waste water is backing up into the property, or a toilet is the only one in the house and unusable, calling out overnight is the right decision. If a gully outside is draining slowly but nothing is backing up, waiting until the morning will cost less and risks nothing. A firm that pushes for an emergency callout on a non-urgent problem is one to be careful with.

Whether the pipe is damaged as well as blocked

This is where a job stops being a fixed price. Clearing a blockage is a defined piece of work. Discovering that the blockage was caused by a collapsed section, a dropped joint or root ingress means a repair, and repairs are quoted separately after a survey. Around Harrow this is common rather than exceptional: the original clay drainage under the older housing stock is well past its design life, and the mature street trees across the borough drive roots into any joint that has opened. If your drain has blocked more than once in a year, the honest expectation is that you are looking at a repair rather than another clearance.

How to get a quote you can rely on

Ask for a fixed price for the clearance rather than an hourly rate, and ask what happens if the blockage is not cleared - a reputable firm will not charge full price for a job they could not complete. Ask whether the price includes a camera check afterwards to confirm the run is clear. Ask what the callout fee is if you decide not to proceed. And before you agree to anything, do the chamber check described in our guide on drain responsibility, because the cheapest outcome of all is discovering the blockage is Thames Water's to clear free of charge.

Common questions

Why does the price change once they arrive?

Usually because the job turns out to need jetting rather than rodding, because access is worse than described, or because the blockage is caused by damage rather than an obstruction. All three are legitimate, but they should be explained and re-quoted before the work starts, not added to the bill afterwards. Ask for the revised price before you agree to continue.

Is a CCTV survey worth paying for?

For a one-off blockage with an obvious cause, generally not. For a drain that has blocked repeatedly, for a property you are buying, or for an insurance claim, it usually pays for itself - it identifies whether you have an obstruction or a structural problem, which determines whether you are facing another clearance or a repair.

Will my insurance cover it?

Blockages caused by ordinary use are almost never covered. Damage to underground pipework - collapse, root damage, subsidence-related movement - is covered by many buildings policies, and some policies also cover the cost of tracing and accessing the damage. See our guide on blocked drains and insurance.