Start from what the surfaces give off
The character of the soiled water is set by the deposit, not by the machine. On a restaurant extraction line you should expect at least three different deposits on one system, and each behaves differently once it is washed.
- Fresh grease and oil mist from the cooking line: soft and wiping, and the first thing a warm rinse moves.
- Cooked-on carbonised film on hot panels and the upper canopy: hard and flaking, released only with heat held against the panel.
- Waxy emulsified residue in the filter pack and at the duct entry: smearing, and the fraction most likely to travel as an emulsion into a drain.
Make the contractor name the deposit on each surface before quoting a method. One blanket label of "grease" hides the fact that the waxy fraction creates the disposal question while the carbonised fraction creates the dwell question. Those are different problems and they carry very different volumes of water.
Ask for the water written down, not estimated
Most arguments about this work happen because nobody recorded the water. Before a method is agreed, require a one-page statement covering four things, filled in for your system and for the specific unit being offered.
- What the machine takes from the mains or a carried tank over a full cycle.
- What actually reaches the canopy, filters and fan housing, including anything that runs off the panel onto the floor.
- What is held on sheets, trays, a sump or a vacuum head, and who removes it.
- What reaches a drain, which drain, and who answers for it.
The value of that statement is that it can be checked. If the contractor can only tell you a figure for "water used", the statement is incomplete, and the missing part is precisely the part that turns into a compliance problem later. A machine that consumes little but leaves most of it on the kitchen floor has not solved anything; it has moved the problem to a place you are answerable for.
Set the water for each surface by what you can reach
Extraction systems are audited by reach. A canopy interior washed from below sends everything downward into the kitchen. A filter pack soaked in a sink gives a known volume that can be contained. A duct entry and a fan housing sit above the line, and whatever is put on them has to fall somewhere.
So the question is per element: how much goes on this element, applied with what, and where does it end up. Where the honest answer is "beyond where the lance reaches, into the duct interior", the scope has to be split and priced separately, and that waste is not the same stream as the canopy wash. Written exclusions that name an alternative beat a quotation that quietly assumes the whole system will be flushed.
This is also where the choice of method shows up in the record. A high-temperature method that loosens a film by holding heat rather than by applying volume trades litres for time, and time in a working kitchen is a cost you carry either way. Neither option is free; the difference is which figure grows. A supplier unwilling to say which one grows on your system is the one to be careful about. Where the duty really does differ from ordinary catalogue use, customized steam cleaning equipment is the route to raise, and the water figures belong inside that enquiry rather than arriving afterwards.
Follow the path from the panel to the drain, step by step
Ask for the route drawn onto the kitchen plan, element by element, and walk it before the work begins.
- The panel: what holds the liquid until it is collected or falls.
- The floor or a collection sheet: whether the kitchen floor is being used as a channel, which is the most common failure in this trade.
- The gully or tray: whether it is sized for the volume the plan says will arrive, and who clears it.
- The interceptor or grease trap: whether it is in the path, whether it is serviced, and whether this job loads it past what it can hold.
- The drain it enters: foul or surface water, and what your own agreement permits there.
A grease interceptor is not a treatment plant for hot, grease-laden wash water; it is a capture device with a service interval. One aggressive clean of a heavily loaded extraction system can fill it beyond that interval in a single morning. Ask who inspects it beforehand and afterwards, who records its condition, and who pays for an early pump-out if the job is what filled it. Those three answers belong in the quotation, not in an argument afterwards.
Check the discharge against permission, not against routine
The kitchen probably already discharges wash water from pot wash and floor cleaning, and the fact that this has always happened is not evidence that a degreasing effluent is allowed. Confirm in writing, before the work: which drain the run-off may enter, whether your supply agreement or discharge consent sets limits on what may enter it, whether hot discharge is restricted, and whether any chemical pre-treatment is permitted upstream of the interceptor at all.
The water authority and the landlord are the two parties able to settle this, and a buyer holding their answer in writing before the job starts is in an entirely different position from one learning of the constraint on the morning of the clean. Where the answer is that the site cannot receive the effluent at all, the option becomes containment and removal by a licensed carrier, and that changes the price. Have it priced before the contract, not during the works.
Compare methods by what they leave behind
Buyers normally compare methods on finish and on labour hours. Compare them on the residue instead, because that is where the cost and the exposure sit.
A chemical soak gives a small volume of difficult character: the detergent itself becomes part of the waste question, and rinsing it off adds water of its own. A hose-and-scrub approach gives a large volume of simpler liquid, easier to reason about but hard to contain above a cooking line. A high-temperature low-volume approach leaves the least liquid to route, which is exactly why it is worth raising for extraction work, but the heat has to be delivered with control over dwell and over what sits nearby, and it does not make the run-off vanish. For work on this class of system, industrial steam cleaning equipment is the category to examine, and the question to put to any supplier in it is what the run-off looks like and where it goes on your plan.
No method should be accepted on a claim that it "produces no waste". The honest version states a volume, a character and a route.
Treat the duct interior as a separate job
The part of the system most often wrecking a water plan is the duct interior, because access, containment and the duties that apply are all different once work is inside the ductwork. This article does not treat internal duct cleaning as part of the same job as canopy, filter and fan-housing work, and you should not let a contractor bundle the two onto one line. Ask who does the internal work, to what standard, with what containment, and who disposes of what it produces. For the accessible panels up to the duct entry, kitchen exhaust duct grease cleaning is the kind of duty to describe in your enquiry so that the quotation covers the right boundary; the boundary itself should be drawn on the plan.
Run one short test that produces figures
A short section of canopy, with the fan isolated and the area below shielded, is the cheapest way to obtain real numbers. Fix the acceptance wording before the first pass, in things you can see: what the panel looks like flat-on and at an angle, what the filter pack looks like afterwards, and what must be dry before cooking resumes at the end of the shift.
Then record while it runs: litres drawn, litres recovered, litres that reached a drain and which one, minutes on the panel, and whether the interceptor showed any load from the run. Write a stop condition in advance, for instance a named panel that must not be attempted or a drain that must not be used, and note whether the test met it. A test that produces impressions is a demonstration. A test that produces figures is something you can attach to the contract.
Put the water into the contract and the working procedure
Once a short test has given figures, the recurring job should carry them. A repeatable extraction-line clean needs the run-off route stated beside every task that uses water, one named person responsible for checking the interceptor, a closing condition that says the area is dry and clear before service restarts, and a frequency set from how hard the line is actually worked rather than from a calendar nobody re-reads.
State the water responsibility by name in the contract: who provides containment, who clears the gully, who arranges a pump-out if the interceptor overloads, and what record comes back with each visit. A specification that describes the finish of the panels but says nothing about the water is not a specification you can sign off, and it is that silence which gets the site charged.
What you can check, and what you cannot
You can check the drawn route for the run-off, the written water statement, the figures from the test, the condition of the interceptor before and after, and the signature on the completion record. You cannot check what happened inside the ductwork, and you should not accept one combined claim covering both the surfaces and the duct interior.
Take published machine data as belonging to the machine rather than to your kitchen. A specification sheet says what a unit can do; it says nothing about what your extraction line can be cleaned into, or where your run-off is allowed to go. The numbers that matter here come from your own test on your own panels and from the answers the authority and landlord give in writing. Choosing the equipment follows from those answers, and it is worth putting the entire duty, water included, to a manufacturer who configures for the site instead of shipping a catalogue unit. That enquiry should carry your list of deposits, the reach limits, the permitted drain and the test figures, so that what comes back is a proposal for your system and not a datasheet.
