Business water for car garages and workshops

An independent garage we work with had been billed against a trade effluent consent that hadn’t been updated since the workshop was extended in 2014. The consent still reflected a single bay handling routine MOT work. The garage now ran two bays plus a small bodyshop. The wholesaler had never been told the operation had grown. The trade effluent line on the bill was wrong in both directions. Under-charged for current activity, but the wrong shape meant several other items on the bill were also off.

Garage water sits in a particular shape. Vehicle washing, parts cleaning, hand wash basins for staff, customer toilets, plus whatever a bodyshop adds in terms of solvents and surface preparation. Almost any garage will have an oil interceptor on the drainage side, which brings trade effluent into the picture.

This page covers how we help UK garages, workshops, MOT centres and bodyshops review their water arrangements. The mechanics of switching are in our main business water switching guide. Our business water service covers the open UK market across every commercial sector.

How we help garages and workshops

We start with the mains water bill, the trade effluent consent if one exists, and a quick layout of the workshop. From there we work through the retail rate, the standing charge, the trade effluent values under the Mogden formula, and any surface water drainage assessment on the yard or forecourt.

For multi-site operators. Chains of MOT centres, regional bodyshop groups. We also handle portfolio consolidation. One retailer with one renewal cycle across the estate.

Why garage water bills are different from a typical SME

Trade effluent and oil interceptors

Almost every garage has an oil interceptor on the drainage side, separating oils and fuel from the water before it enters the sewer. The interceptor doesn’t remove the trade effluent requirement. It just means the water that does enter the sewer is in a state the wholesaler is willing to accept under consent.

The consent and Mogden formula values are usually set when the workshop is built or first inspected. They rarely get updated. If the workshop has been extended, modernised, or had its process changed, the consent is probably out of date.

Yard and forecourt drainage

A typical garage has a forecourt, customer parking, a vehicle handover area, and often a separate area for cars awaiting MOT or repair. All of that is impermeable area. Where it drains to the public sewer, surface water drainage charges apply.

Many modern garage sites have separate surface water drainage running to a soakaway, attenuation pond or licensed outfall. Where that’s the case, the SWD line on the bill may not match the actual drainage arrangement. The standard look-back for a corrected SWD assessment is six years under the Limitation Act 1980.

How a garage water review works