water-and-oil

---
name: water-and-oil
description: Produces one dated file on the two bills a hospitality business almost never reads - the water bill broken into its parts with the surface water drainage charge tested against where your rain actually goes, and the used cooking oil route checked against the law that makes pouring it away a criminal offence. Use before you renew a water contract or a waste oil collection, when a drain blocks and somebody mentions a grease trap, or when you have simply never looked at what the water bill is made of.
---

# Stop paying for rain that never reaches the sewer, and find out what your oil is worth

You give this your last four water bills, your meter number, a plan or photograph of where the rain goes on your site, your drainage and grease equipment, and your used cooking oil arrangement. You get back one dated file: the water bill separated into clean water, wastewater, surface water drainage, highway drainage and standing charges; the surface water charge tested against your actual drainage with the wording to claim a reduction; the trade effluent and grease positions with the sections that govern them; and the oil route with the questions to put to your collector. It does not tell you a refund is owed. It shows what your bill charges for and what the published rule says, so you can ask.

## What it does

1. **Separate your retailer from your wholesaler, because they are two different companies and only one of them you can change.** In England the non-household retail market opened on 3 April 2017, when, as GOV.UK put it at the time, "over 1.2 million 'eligible' non-household customers in England can choose their water supplier". That page defines eligible customers as "non-household premises that pay business rates" and was withdrawn on 2 August 2024, so treat it as historic context rather than current guidance. The Consumer Council for Water states the present position in one line: "If you run a business in England, you can shop around for a better water deal." Your retailer sends the bill, reads the meter and is the company you switch. The wholesaler owns the pipes, sets most of the charges and does not change when you switch. Write both names into the file, because half the frustration in this subject comes from ringing the wrong one.

2. **Break the bill into its parts and write each one down separately, because the total tells you nothing.** A non-household water bill is usually five or six things added together: clean water by volume, wastewater by volume, surface water drainage, highway drainage, fixed or standing charges, and the retailer's own margin. Take each from the bill itself rather than an annual statement, and record for every line the period, the figure, and whether the meter read behind it was actual or estimated. A bill built on estimated reads is not a measurement of anything. If the bill does not separate surface water drainage from wastewater, that is the first written question to the retailer.

3. **Test the surface water drainage charge against where your rain actually goes, because this is the one line most often charged wrongly.** The rule as published by one wholesaler is specific: "If more than 10% of your surface water does not drain to the public sewer (either directly or indirectly through a drain or watercourse), you may be eligible for a reduction in your surface water charges." Walk the site and follow the water. A yard draining to a soakaway, a roof discharging to a watercourse, a car park on a separate system, or a flat roof over an extension that was never connected all count. The claim goes through the retailer: "you can contact your retailer to claim a reduction in your surface water charges." Then move fast, because the money runs out backwards. The Consumer Council for Water records that "Water industry regulator Ofwat only insists that companies refund surface water charges to the start of the current year". A charge paid wrongly for nine years may be refundable for one.

4. **Read the meter twice on a closed night and find out whether you have a leak before you argue about tariffs.** Take a meter reading at lock-up and another at open, write down both readings with the exact times, and subtract. Anything more than a trickle on an empty building is a leak, a running urinal, a faulty ice machine fill valve or a cistern that never shuts. This is measurable in half a minute and is usually worth more than any tariff conversation. Where the bill disagrees with two readings you photographed, that is a dated billing question, not a measurement problem, and it goes in the file as an open item.

5. **Settle the trade effluent question, because it is a consent and not a charge.** Section 118(1) of the Water Industry Act 1991 provides that "the occupier of any trade premises in England in the area of a sewerage undertaker may discharge any trade effluent proceeding from those premises into the undertaker's public sewers if he does so with the undertaker's consent". Note who the duty falls on: the occupier, which in a leased pub or restaurant is you and not your landlord. Most ordinary kitchen wastewater is not treated as trade effluent, but some processes are, and the only way to know is to ask the wholesaler in writing whether a consent is held or required here, and keep the answer with its date. An assumption inherited from the previous tenant is not an answer.

6. **Understand that fat down the drain is a criminal offence and not a plumbing nuisance, because that changes who takes it seriously.** Section 111(1) of the Water Industry Act 1991 provides that "no person shall throw, empty or turn, or suffer or permit to be thrown or emptied or to pass, into any public sewer, or into any drain or sewer communicating with a public sewer ... any matter likely to injure the sewer or drain, to interfere with the free flow of its contents or to affect prejudicially the treatment and disposal of its contents". Section 111(3) makes contravention an offence, punishable on summary conviction by a fine up to the statutory maximum "and to a further fine not exceeding £50 for each day on which the offence continues after conviction", and on indictment by "imprisonment for a term not exceeding two years or to a fine or to both". Thames Water says the same thing to food businesses: "It's a criminal offence under section 111 of The Water Industry Act 1991 to release anything into the public sewers that could interfere with the free flow of wastewater." Notice the words "suffer or permit". Not knowing a pot wash was being emptied into a gully is not a defence.

7. **Check whether the building has the grease separator the Building Regulations expect, and whether anybody maintains it.** Approved Document H to the Building Regulations is unambiguous at paragraph 2.21: "Drainage serving kitchens in commercial hot food premises should be fitted with a grease separator complying with BS EN 1825-1:2004 and designed in accordance with BS EN 1825-2:2002 or other effective means of grease removal." Thames Water states it as a duty: "If your business serves hot food, by law you need to have a grease separator installed (Building Regulations Part H 2002)." So record three things, not one: whether a separator or other effective means of grease removal exists, what it is and where, and the date it was last emptied and by whom. An unmaintained grease trap is worse than none, because it looks like the problem is handled while it passes grease straight through.

8. **Treat used cooking oil as a waste with a legal route and a market value, and ask your collector which of those they are giving you.** The rule on storage and collection is flat: "If you produce waste cooking oil as part of your catering business, then you must ensure that it is stored properly. No oil is allowed to spill and it has to be collected by an authorised collector", who takes it "to an authorised site for recovery or disposal". Two routes are closed. Down the drain: "Waste cooking oil must not be poured down drains or sewers because this causes: blockages, bad smell, vermin problems, polluted watercourses leading to problems for wildlife", and doing it "can result in potential prosecution". And into any animal: "Anyone using scraps and catering waste, including waste cooking oil from catering premises commits an offence if it is used as: animal-feed, an ingredient in animal-feed, part of animal feed operations." Then ask the commercial question nobody asks: is the collector charging you, collecting free, or paying you per litre, and what is the litre volume. Record the answer with a date. The carrier registration and the transfer note belong with your waste duty of care records rather than here.

9. **Build the register, date it, and fix the day you will read it again.** One page for water: retailer, wholesaler, meter number, each bill line with its period, figure and read type, the surface water finding and the claim date, the trade effluent question and its answer. One page for oil and grease: the separator, its maintenance dates, the collector, the terms, the litres and the questions outstanding. Date the file, record when each source was read, and diary the re-read. Surface water claims lose value every month they are not made, and a grease separator with no maintenance date on file is one somebody will assume is fine.

## Then it checks

1. The file names the retailer and the wholesaler separately, with the meter number, and does not use the word supplier to mean both.
2. Every bill line is recorded with its period, its figure and whether the meter read behind it was actual or estimated, and no figure is taken from an annual summary in place of a bill.
3. The surface water finding states where the rain on each part of the site actually goes, how that was established, and the date any claim was made to the retailer, rather than stating that a refund is due.
4. The meter readings behind any leak finding carry exact dates and times and the name of the person who read them.
5. The grease position records whether a separator or other effective means of grease removal exists, what it is, and the date it was last emptied and by whom, with an unknown recorded as unknown rather than left blank.
6. The oil arrangement names the collector, states whether the site pays, receives or neither, and records the litres from a document, and the file states nowhere that the site complies with section 111, section 118 or the Building Regulations.

Any check fails: name it, redo that step once. Failed twice: say what is wrong and stop.

## Rules
- Public information only.
- Never invent a fact, a number or a quote.
- Anything sent in someone's name says whose name it is. A surface water claim or a trade effluent question goes out over the name of the person who will have to answer the reply.
- Never tell an owner a refund is due, that a consent is not required, or that their drainage complies. Those are determinations for the retailer, the wholesaler and the local authority building control body, and an owner told "you are fine" stops asking the people who could actually tell them.
- Refuse to describe any arrangement for putting fats, oils or food waste into a drain, a gully or a public sewer, however diluted, however small the quantity, and whatever the site's constraints. It is an offence under section 111 and there is no operational reason that changes that.
- Never state a benchmark for litres of water per cover, a typical surface water charge, a typical oil yield or a percentage saving from switching retailer. No published figure exists for a single independent UK venue, and an owner who budgets from a borrowed number will conclude their own site is failing.
- Never treat a collector's or a retailer's verbal assurance as established. Record who said it and on what date, and leave it open until a document, a consent reference or a credit on a bill arrives.
- Never carry a rebate rule or a charging structure forward from an earlier file without re-reading the source. Wholesaler charging schemes are reissued annually and the terms of a surface water reduction differ between companies.
- This output is a working document prepared for the owner to check with their water retailer, their wholesaler, their building control body and their waste oil collector before it is relied on. It records what the bills say, what the drainage does and what the published rules require, and names the gaps. It is not legal advice and it does not certify compliance.

## Built from
- Water Industry Act 1991, section 111 "Restrictions on use of public sewers", https://www.legislation.gov.uk/ukpga/1991/56/section/111, read 16 September 2026: the prohibition on matter likely to injure the sewer or interfere with the free flow of its contents, the "suffer or permit" wording, and the penalties at section 111(3), all in step 6.
- Water Industry Act 1991, section 118 "Consent required for discharge of trade effluent into public sewer", https://www.legislation.gov.uk/ukpga/1991/56/section/118, read 16 September 2026: the consent requirement and the fact that it attaches to the occupier of the trade premises, in step 5.
- Ministry of Housing, Communities and Local Government, "The Building Regulations 2010, Approved Document H: Drainage and waste disposal", 2015 edition, paragraph 2.21, https://assets.publishing.service.gov.uk/media/5a80cf9ded915d74e33fc8ae/BR_PDF_AD_H_2015.pdf, read 16 September 2026: the grease separator provision and the BS EN 1825-1:2004 and BS EN 1825-2:2002 references in step 7.
- Thames Water, "Preventing blockages for food businesses", https://www.thameswater.co.uk/wholesale/best-practice-for-food-businesses, no publication date shown on the page, read 16 September 2026: the statement that discharging fats, oils, greases and food waste into sewers is illegal, the section 111 wording addressed to food businesses in step 6, and the grease separator duty for hot food premises in step 7.
- Food Standards Agency and GOV.UK, "Food and cooking oil waste", https://www.gov.uk/government/publications/food-and-cooking-oil-waste/food-and-cooking-oil-waste, published 22 May 2018, read 16 September 2026: the storage and authorised collector requirement, the prohibition on pouring oil down drains or sewers with its consequences, and the animal feed offence, all in step 8.
- United Utilities, "How to reduce my surface water and highway drainage charges", https://www.unitedutilities.com/Business-services/business-customers/site-area/how-do-i-reduce-my-surface-water-and-highway-drainage-charges/, no publication date shown on the page, read 16 September 2026: the more than 10% test and the instruction to claim through the retailer, in step 3.
- Consumer Council for Water, "Do your water charges fit the bill?", https://www.ccw.org.uk/news/do-your-water-charges-fit-the-bill/, published 31 August 2016, read 16 September 2026: the definition of surface water drainage charges, the instruction to call the sewerage company and apply for a rebate, and the Ofwat position that refunds run to the start of the current year, in step 3.
- Consumer Council for Water, "Business customers", https://www.ccw.org.uk/advice-and-support/businesses/, no publication date shown on the page, read 16 September 2026: the current statement that a business in England can shop around for a better water deal, in step 1.
- GOV.UK, "Choose a water supplier for your business", https://www.gov.uk/guidance/what-is-happening-in-the-water-market, published 30 November 2016, last updated and withdrawn 2 August 2024, read 16 September 2026: the opening of the market on 3 April 2017 and the definition of eligible non-household premises, used in step 1 and expressly flagged there as withdrawn and historic.

This is a working document prepared for the owner to check with their water retailer, their wholesaler, their building control body and their oil collector before it is relied on. It is not legal advice and it does not certify compliance.

# water-and-oil

## You are given
One UK hospitality site's water and used cooking oil position, already judged by Claude. Specifically: the site name and address and its tenure; the water retailer's name and account number and the wholesaler's name; the meter serial number and location; the last four water bills broken by Claude into their component lines, each line carrying its charge type, period start and end, figure in pounds, volume in cubic metres where volumetric, and whether the meter read behind it was actual or estimated; a drainage description for every part of the site naming the area and where its surface water goes, with how that was established; the lock-up and open meter readings with their exact dates and times and the person who read them; whether a trade effluent consent is held, with its reference and date, or the date the question was put to the wholesaler; the grease removal equipment with its type, location, last emptying date and the contractor; the used cooking oil collector, the commercial terms, the litres collected per visit from a document, and the collection frequency; every written question put to a retailer, wholesaler, contractor or collector with the date asked and the answer; and the quoted source wording Claude relied on, each with its source URL and the date it was read. Where a figure or judgement is missing it arrives as the words `not supplied`.

## Produce
Write into a `./water-and-oil-output/` folder:

1. `bill-breakdown.csv` with these columns in this order: `bill_ref`, `period_start`, `period_end`, `charge_type`, `amount_gbp`, `volume_m3`, `read_type`, `retailer`, `wholesaler`, `meter_serial`, `source_document`. `charge_type` is exactly one of `clean water volumetric`, `wastewater volumetric`, `surface water drainage`, `highway drainage`, `standing or fixed charge`, `retailer margin`, `other`, `not supplied`. `read_type` is exactly one of `actual`, `estimated`, `not supplied`. `source_document` names the bill, never an annual summary.
2. `surface-water.csv` with columns: `area_ref`, `area_description`, `area_m2`, `drains_to`, `reaches_public_sewer`, `how_established`, `evidence_held`, `share_of_site_percent`, `threshold_percent`, `claim_made_date`, `claim_reference`, `retailer_response`, `source_url`, `source_read_date`. `drains_to` is exactly one of `public sewer`, `soakaway`, `watercourse`, `separate system`, `unknown`. `reaches_public_sewer` is `yes`, `no` or `unknown`. `threshold_percent` is copied from the input and never altered. No column states that a refund is due.
3. `leak-check.csv` with columns: `lockup_date`, `lockup_time`, `lockup_reading`, `open_date`, `open_time`, `open_reading`, `hours_elapsed`, `volume_m3`, `litres_per_hour`, `read_by`, `building_empty_confirmed`, `billing_query_raised_date`. `litres_per_hour` is computed only where both readings and both times are present, and is left empty otherwise. `building_empty_confirmed` is `yes`, `no` or `not supplied`.
4. `consents-and-equipment.csv` with columns: `item`, `type`, `location`, `legal_reference`, `consent_or_standard`, `held`, `reference_number`, `date_obtained_or_asked`, `last_maintained_date`, `maintained_by`, `next_due`, `source_url`, `source_read_date`. One row for the trade effluent position and one for each item of grease removal equipment. `held` is exactly one of `yes`, `no`, `asked and not answered`, `unknown`, `not supplied`. `last_maintained_date` left unknown is written as `unknown`, never blank.
5. `oil-route.csv` with columns: `collector_name`, `authorised_collector_confirmed`, `confirmation_document`, `collection_frequency`, `litres_per_collection`, `litres_source`, `commercial_terms`, `price_per_litre_gbp`, `annual_litres`, `annual_value_gbp`, `date_terms_confirmed`. `commercial_terms` is exactly one of `site pays`, `collected free of charge`, `site is paid`, `not supplied`. `litres_source` is exactly one of `collection note`, `invoice`, `weighed on site`, `not supplied`, and `annual_litres` and `annual_value_gbp` are left empty where `litres_source` is `not supplied`.
6. `prohibited-practices.md` - a short file listing, in plain sentences, every practice observed or reported on site that puts fats, oils, grease or food waste into a drain, a gully or a public sewer, with the section 111 wording quoted against each and the date each was observed and by whom. Where none was observed the file says so in one sentence with the date of the walk. It never describes, designs or suggests any such practice.
7. `questions-outstanding.csv` with columns: `addressee`, `organisation`, `question`, `date_asked`, `asked_by`, `date_answered`, `answer_verbatim`, `days_open`, `status`. `status` is exactly one of `answered`, `asked and not answered`, `not yet asked`.
8. `gaps.md` - a numbered list of: every bill line with an `estimated` read; every bill with no separate surface water drainage line; every site area whose `drains_to` is `unknown`; any surface water finding over the supplied threshold with no `claim_made_date`; any leak check missing a reading or a time; any consent or equipment row reading `unknown` or `asked and not answered`; any oil figure with `litres_source` of `not supplied`; every outstanding question with its days open; any missing source URL or read date; and the date fixed for the re-read.

## Rules
- Codex measures, separates, computes and records. It never invents, never estimates a volume, a litre count or a charge, never rewords a bill line or a retailer's reply, and never makes the entitlement or compliance judgement that was supplied to it.
- Never write that a refund is due, that a reduction will be granted, that a trade effluent consent is not required, or that the site's drainage or grease equipment complies. None of these goes into any file.
- Never describe, design, suggest or record as acceptable any route that puts fats, oils, grease or food waste into a drain, a gully or a public sewer. `prohibited-practices.md` records what was found and quotes the prohibition against it, and nothing else.
- Never take a figure from an annual statement where a bill was supplied, and never merge two charge types into one row because the bill printed them together. Where the bill does not separate them, the row's `charge_type` is `not supplied` and the bill is listed in `gaps.md`.
- Never write a benchmark, an industry average, litres per cover, a typical surface water charge, a typical oil yield or a percentage saving. No such figure exists for a single independent UK venue and none is to appear in any file.
- Never record a legal requirement without its source URL and the date that source was read, both copied from the input.
- A missing maintenance date is written as `unknown` and appears in `gaps.md`. It is never left blank and never inferred from a contract or an invoice for something else.
- Use British English, GBP for money, cubic metres and litres for volume, and DD Month YYYY for every date. No em dashes in any file you write, and any supplied text containing one is recorded verbatim and flagged in `gaps.md`.
- Every file ends with this line: this is a working document prepared for the owner to check with their water retailer, their wholesaler, their building control body and their oil collector before it is relied on; it is not legal advice and it does not certify compliance.

## Return
The absolute path of each file written, the row count of each CSV, the retailer and wholesaler names and the meter serial, the total billed by charge type across the four periods with the number of periods carrying an estimated read, the proportion of the site whose surface water does not reach the public sewer against the supplied threshold and whether a claim date exists, the litres per hour from the leak check with the dates and times of both readings, the trade effluent position as recorded with its reference or the date the question was asked, every item of grease removal equipment with its last maintained date including any recorded as unknown, the oil collector with the commercial terms and the annual litres and value where computable, the number of entries in `prohibited-practices.md`, the number of questions outstanding with the oldest date asked, the re-read date, and the `gaps.md` item count.