Is Your Business Overpaying for Water? A Quick Audit Guide

Billing errors have become surprisingly common in the UK's deregulated water market. Although this has lead to businesses being able to easily switch suppliers, this also mean that the wholesaler still treats and delivers the water through the same pipes.

This has ended up bringing billing complexities, causing businesses being charged for water they might not have been using. In 2025-2026, billing issues made up nearly half of all complaints business customers sent to their retailers, and 90% of the cases that reached the Consumer Council for Water. Even when charges were based on meter readings, measured billing (when charges are based on meter readings) accounted for over half of those.

None of this requires a consultant. A short site check plus a look through your last year of bills usually surfaces the same issues an external auditor would find.

1. What a Water Audit Actually Checks

A proper commercial water audit covers three things, and it's worth going through all three before you start.

Billing analysis This involves going through past bills to validate meter readings and making sure there are not any extra charges or incorrect allowances.

Site tariffs Separately from what's on the bills, it's worth checking that the tariff itself matches your property type and size rather than a default rate.

The site itself. This is an on site physical walk-through of your site to catch waste leaking pipes, running cisterns, outdated fittings.

Unless you are a large site, it is very much possible to run a basic version of the three steps above in-house and catch potential issues with your billing.

2. Potential issues with your billing

Billing complaints make up most of everything sent to water providers, according to the Consumer Council for Water. So if your invoice looks off, you're far from alone. You can start by obtaining all your water bills in the last year and check for the following. Note that most retailers allow you download this from their portal but in the case they don't, you can always ask.

• Estimated readings. An "E" next to a reading means your retailer guessed your usage from history rather than reading the meter. If your usage has dropped since, submit your own reading and ask for a reconciliation.

Surface water drainage charges. This covers rainwater draining from your property into the public sewer, and how it's calculated varies a lot by wholesaler. Some (Yorkshire, Northumbrian, Severn Trent) now charge by actual site area; others (Anglian, Southern, Thames, Wessex) fold it into the standing charge instead; Scottish Water still uses rateable value. Two things to check: is your area banding accurate (it's based on an estimate, not a measurement, so it's often wrong), and does your rainwater actually reach the public sewer at all? Switching to the right charge type could lead to you saving a lot on your next bill.

Meter size and standing charges. Standing charges scale with your meter size. It's common for a business to move into a unit sized for a previous tenant's higher usage, like a small office or shop that used to pay standing charges built for a much bigger operation.

Return to sewer allowances. Wastewater charges assume that most of what you draw in goes back down the drain. If a meaningful share of your water doesn't because it ends up in your product, like a brewery, bakery or for irrigation, you can apply for a Return to Sewer Allowance to stop paying for water you never sent back. This isn't limited to large manufacturers: smaller operations like landscapers, bakeries, or any site using a private soakaway can qualify too.

Checking for Physical Waste

Once the paperwork's covered, it's worth spending twenty minutes checking the site itself. Small leaks add up fast.

• Overnight meter test: Read your meter at the end of the day once everything's switched off, then again first thing before anyone arrives. Any movement means a leak somewhere.
• Visual checks: Look over exposed pipework, your boiler, and toilet cisterns. A leaking cistern typically wastes 200–400 litres a day, and the fix is usually just a £5 flapper valve.
• Flow rates: Check the output on taps and showerheads. Low-flow aerators can cut washroom water use by up to half without anyone noticing a drop in pressure.

If it turns out you were being overcharged

Take what you've found straight to your current retailer, with the bills to back it up. You can generally claim refunds for up to six years of historic overcharging under the standard statute of limitations, though the exact window depends on your contract and the type of error, which is exactly why keeping old bills on hand matters.

If the billing checks out but the rate itself is just high, you can switch. Wholesale charges are fixed regardless of retailer, so switching mainly saves on retail margin (2–7%), with bigger savings usually coming from the audit itself. You can switch mid-dispute too: keep paying the undisputed portion, and any refund owed stays live as a separate claim after you've moved.

FAQs

Can I switch suppliers while disputing a bill? Yes. Keep paying undisputed charges in the meantime, an unpaid balance can let your current retailer block the transfer.

How much does a commercial water audit cost? Nothing, if you do it yourself. External auditors typically work no-win, no-fee, taking a cut of whatever they recover.

Can Welsh businesses switch retailer? Only above 50 megalitres a year. Below that, a bill and drainage check is still worth doing even if switching isn't an option.

Are SMEs eligible for a return to sewer allowance? Yes, regardless of size. It's common among breweries and manufacturers, but bakeries, landscapers, and any business using a private soakaway can apply too.

My water bill went up. Can I get the old charges refunded if they were wrong? If you have been overcharged, CCW's position is that no time limit applies to your refund, though rebates are commonly backdated six years from the application date. The reverse is capped: if you have underpaid, a retailer can generally only back-bill you 16 months, or 24 months in limited disputed cases.