How Much Does Channel Drain Installation Cost? What Sets the Price

How much channel drain installation costs depends less on the channel itself than on three other things: where the collected water is going to go, what surface has to be cut open and put back, and which load class the channel must carry. A short plastic channel across a patio door that runs into an existing gully is a small job. A run across a block-paved driveway that needs a new soakaway or a new connection is a different job with a very different price. This guide explains each item behind a channel drain quote so you can see what you are paying for, and when a channel drain is not the fix you need.

What is a channel drain, and when do you actually need one?

A channel drain, also called a linear drain or by trade names such as ACO drain, is a narrow trough with a grating on top, set into a paved surface to catch rainwater along a line. You need one when water runs across a hard surface towards a building, a door or a garage and there is no gully in the right place to catch it.

The usual London reasons for fitting one are:

• A driveway that falls towards the house or the garage, so rain collects against the wall or under the door.
• A patio or level-access door where water pools at the threshold after heavy rain.
• A newly paved front garden that has to drain properly to avoid needing planning permission.
• A yard or car park where surface water lies in one area and freezes in winter.

If water is only pooling because an existing gully is blocked, you do not need a channel drain. Clearing the gully is far cheaper, and our guide to what it costs to unblock an outside drain covers that job.

Where does the water go, and why does that set most of the price?

A channel drain only moves water to its outlet, so the cost of getting that water somewhere acceptable is often larger than the cost of the channel. The three options are an existing drain, a new soakaway, or a new connection to a sewer.

An existing surface water drain or gully nearby is the cheapest outlet. The channel runs to it, with a short pipe and an outlet box, and little else is needed.

A new soakaway is needed when there is nothing suitable to connect to. Approved Document H to the Building Regulations puts soaking water into the ground first in its order of preference, so this is often the expected answer. It adds excavation, materials and spoil removal, and on London clay a soakaway can be large or unworkable. Our guide to what sets the price of a soakaway explains why.

A new connection to a public sewer is the last resort. Rainwater must never go into a foul-only drain, and a new connection to a public sewer needs the sewerage undertaker's consent under section 106 of the Water Industry Act 1991. The application, and any fee charged for it, is a separate cost from the drainage work.

A quote that prices the channel but says nothing about where the water goes is not a complete quote.

Which load class do you need, and does it change the cost?

Yes. The channel and grating must be rated for the heaviest traffic that will cross them, and higher load classes cost more. Channel drains are classified under BS EN 1433, and the class should be written on the quote.

• A15 is for pedestrian areas only, such as patios, paths and door thresholds.
• B125 is the usual class for domestic driveways and car parks used by cars.
• C250 and above are for kerbside areas, service yards and anywhere delivery vans or lorries turn.

Fitting a pedestrian-rated grating across a driveway is a common way to make a quote look cheaper. The grating cracks or the channel moves under the first few months of car wheels, and the job has to be done again. Paying for a higher class than you need is also wasted money, so ask why a class was chosen.

What else goes into a channel drain installation quote?

Beyond the channel and grating, a quote should cover cutting out the surface, bedding the channel, the outlet, reinstatement and taking the waste away. These lines are where two quotes for the same length of channel usually differ.

• Cutting and breaking out. Saw-cutting a neat trench through concrete or tarmac takes longer than lifting block paving, which can often be relaid.
• Concrete bed and haunching. Channel drains are set on and surrounded by concrete so they do not move. Skipping this is the main reason cheap installations fail.
• Falls. The surface has to fall towards the channel. If it currently falls the wrong way, part of the paving may need relaying, and that should be priced as its own item.
• Outlet box or silt trap, so debris can be removed without digging anything up.
• Reinstatement. Relaying blocks is cheaper than patching resin-bound gravel or matching old concrete. Patch repairs on resin or tarmac rarely match exactly, and a good quote says so.
• Spoil and waste removal from the trench.
• Time band. Channel drain work is planned work and belongs in standard hours on our published rate card, not in an evening or night band.

Do you need planning permission for a new driveway drain?

Not for the drain itself, but the drainage can decide whether the paving needs permission. In England, paving more than five square metres of a front garden with an impermeable surface needs planning permission unless the water runs to a permeable area or a soakaway within the property.

That is why front driveways are often fitted with a channel drain that feeds a soakaway or a rain garden. If you are paving a front garden, the drainage is part of the planning question, not an extra added at the end. Check with your council's planning department if you are unsure, because the cheapest paving job can become the most expensive one if it needs to be taken up.

When is a channel drain the wrong answer?

When the problem is not surface water crossing a hard surface. Paying for a channel drain in these situations moves the water around without fixing the cause.

• A blocked or collapsed drain. If water is coming up out of a gully or a manhole, the drain below is the problem. A camera check will show whether it needs clearing or repair, and that is a different job with a different price.
• Nowhere for the water to go. On heavy clay with no surface water sewer nearby, a channel drain feeding an undersized soakaway just stores the puddle underground until it overflows.
• Damp walls from a high path or bridged damp course. Lowering the ground next to the wall can matter more than catching the water.
• A leaking gutter or downpipe pouring onto the paving. Fixing the gutter is cheaper than draining the result.

How do you compare channel drain quotes?

Compare what each quote does with the water and how the channel is installed, not only the price per metre. A low price per metre with no outlet, no concrete bed and a pedestrian grating is not comparable with a quote that includes all three.

Ask each installer: how long the run is and what load class they are fitting; where the water goes and whether that connection or soakaway is included; whether the channel is bedded and haunched in concrete; what surface they are cutting and how it will be reinstated; whether a silt trap or outlet box is included; and whether VAT is included. A quote that answers every question is one you can compare. If you would like one set out in that way, send us the details and photos and we will say which items apply to your site.