Foul Sewage Assessment or Utilities Assessment

If you are asking whether you need a foul sewage assessment or utilities assessment, the short answer is that they answer different questions and a new dwelling often needs both. A Foul Sewage Assessment deals with one thing: where the wastewater goes, and whether the receiving system or the ground can take it lawfully. A Utilities Assessment covers the rest of the services, which means water supply, electricity, gas and telecoms capacity, and the physical routes to bring them onto the site.

Councils treat them differently at validation too. Foul drainage is a question on the application form itself, so an unanswered or implausible answer can hold up validation. Utilities capacity rarely appears on a local validation list for a minor scheme, and then it bites later, when the distribution network operator quotes six figures for a reinforcement you did not budget for.

Foul drainage against the wider utility picture

The overlap is water supply. A Water Supply Assessment belongs with the utilities work in most cases, though in water stressed catchments it becomes a policy matter in its own right and the authority will want to see demand figures, not just a connection point.

The right to connect and its limits

Section 106 of the Water Industry Act 1991 gives the owner or occupier of premises a right to have their drains communicate with the public sewer. It is a real right and a useful one to quote when an undertaker is being difficult. It is also qualified.

The undertaker can refuse where the mode of construction or condition of the drain is unsatisfactory, or where the connection would be prejudicial to its sewerage system. Capacity, in practice, is where most refusals and most conditions come from. On a constrained network you may be offered a connection subject to flow attenuation, a phased occupation trigger, or a requirement to wait for a scheduled upgrade.

Where there is no sewer within a reasonable distance, section 98 lets you requisition one, with the cost shared under a statutory formula. Few small developers go down that route because the commuted payments are heavy, but it exists and it is worth pricing against an on site treatment solution.

Capacity enquiries and pre development enquiries

Start the enquiries before the layout is fixed. Each undertaker runs its own pre development or capacity enquiry service, and the published turnaround is usually measured in weeks rather than days.

1. Submit a pre development enquiry to the sewerage and water undertaker with the site boundary, unit numbers and indicative phasing.
2. Ask for sewer records (asset plans) at the same time, so you know what crosses the site before you draw anything.
3. Submit a point of connection enquiry to the electricity distribution network operator with your estimated maximum demand, including any heat pumps and electric vehicle charging.
4. Ask the gas transporter whether a connection is viable at all, because many all electric schemes now skip gas entirely.
5. Log the telecoms position. New build developments are expected to be served with gigabit capable connections, and Part R of the Building Regulations requires in building physical infrastructure.

The answers change the design. A foul connection that has to run uphill needs a pumping station, which needs a location, an access track, an adoption agreement and a noise and odour position that the Drainage Strategy has to explain.

Non mains drainage and the general binding rules

Rural sites usually come down to a package treatment plant or, less often now, a septic tank. The hierarchy in the Planning Practice Guidance and in the application form is clear: mains connection first, then a package treatment plant, then a septic tank, with a cesspool as the last resort.

A small sewage discharge can operate under the Environment Agency's general binding rules rather than a bespoke permit, provided the discharge stays within the volume limits and the other conditions are met. Discharges to ground are limited to 2 m³ a day and discharges to surface water to 5 m³ a day under those rules, with higher volumes needing a permit. Septic tanks discharging directly to a surface water body have not been acceptable since 1 January 2020 and had to be replaced or redirected to a drainage field.

Two points get missed on planning submissions. The drainage field needs a percolation test to BS 6297 and enough space at the right separation distances, which is a layout constraint, not a detail for later. And the discharge point has to be land you control or have rights over, which on a plot sold off a larger holding is frequently not the case.

A Foul Sewage Assessment that states the chosen method, the calculated daily flow, the percolation result and the general binding rules compliance position answers the officer's question in one document.

Building over or near a public sewer

If a public sewer crosses the site, the undertaker's build over or build near agreement is a separate consent from planning permission, and getting one does not follow automatically from the other. Standard easement widths are commonly 3 m either side of the pipe centreline for smaller sewers and more for larger ones, though each undertaker publishes its own requirements.

The usual outcomes are a diversion at your cost, a build over agreement with conditions on foundation design and access to manholes, or a redesign that keeps structures clear. Diversions take months. Build the enquiry into the programme at the same time as the pre-application, and read the evidence base for development near a public sewer before you commit to a footprint that sits on the line.

Electricity, gas and telecoms capacity

The electricity position has changed faster than most planning submissions acknowledge. All electric heating, electric vehicle charging points required under Part S and the loss of gas as a default have pushed estimated maximum demand up on schemes of every size.

What that means in practice: a site that would have taken a simple service connection five years ago may now need a new substation. A substation needs a site, usually at least 3 m by 3 m with vehicular access and clear of trees and drainage, and it needs to be shown on the planning layout. Finding out after permission that the only viable location is in the middle of the approved frontage is a familiar and avoidable problem.

Routes matter as much as capacity. A connection that has to cross third party land needs a wayleave or easement, and one that runs along the public highway needs a street works permit from the highway authority. Both have lead times that sit outside your control.

Which enquiries to start first

Order them by how badly a bad answer would hurt the layout:

• sewer asset records and the build over position, because a pipe across the site changes the footprint
• foul disposal method and, for non mains sites, the percolation test and drainage field location
• electricity point of connection and whether a substation is needed, because it needs a plot
• water supply, pressure and any catchment specific demand requirement
• telecoms and gas, which rarely change a layout

On a single plot the whole exercise can be a morning's work and two emails. On a 40 unit site it is a workstream, and the Utilities Assessment is where the answers get written up for the officer rather than sitting in a consultant's inbox.

Neither document is a substitute for the formal consents. A build over agreement, a section 104 adoption agreement, a permit for a larger discharge and a connection offer are all separate processes with their own fees and timescales, and planning permission does not deliver any of them.

This is general guidance, not legal advice. Check the position with your local planning authority, your sewerage undertaker or a qualified professional before relying on it.

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