Three water costs, and only one of them is on a meter
Water on a vessel trial shows up in three ledgers at once, and teams routinely read only the first. Supply is the volume drawn from the marina or yard connection across the job, the figure that appears on the facility's bill and that a metered draw can actually prove. Run-off is the water that leaves the hull and deck and has to be caught, diverted or discharged under whatever the site itself permits; on afloat work it falls by gravity to the waterline, on a hardstand it follows the deck plan. The third cost is invisible until it is counted: water spent on a stage that had to be redone, because an area was missed, a deposit was not lifted on the first pass, or a rinse was judged against no agreed finish.
A cleaning programme can therefore sit in an uncomfortable position. It draws less at the lance than the method it replaced, while quietly consuming more in repeat passes than anyone recorded. The three costs have to be measured separately or the savings claim collapses as soon as somebody checks the meter.
Define the unit of work as places, not time
Water per hour is the wrong denominator for a hull or a deck, because an hour on a clean topside and an hour on a salted boot-top are not the same job. The unit worth recording is a place: the run of hull side from the rubrail to gunwale on one panel between frame stations, the topside deck from the stem fitting to the mast step, the transom face, the anchor locker surround and chain run, the coachroof side, the swim platform and its face, and the ladder stowage. Those units are stable across crews and across vessels of the same class, which is exactly what a consumption figure needs to be comparable.
Once work is measured in places, the consumption figure gains an honest denominator: volume per unit, plus the pass count it took to bring that unit to the agreed finish. A figure per hour cannot be challenged in a useful way. A figure per unit can, because a supervisor can walk the unit, see the finish and ask how many times the tool went over it.
Meter at the supply, not at the nozzle
On afloat work the supply may be a hose from a marina pedestal, a dockside tap, or the boat's own tank when a unit feeds from it. Each route needs its own reading method, and the reading point should be the point where the volume is committed. Where the machine has a tank, refill counting is the crude instrument: fills per unit, multiplied by the fill volume. Where the machine takes mains water through a fitting, an in-line meter on that line is the only defensible record, because the volume then commits at the connection instead of inside a tank someone has to open.
One caution. The absence of a meter does not mean the absence of consumption. A vessel trial fed from the boat's tank makes the boat's own supply the limit, so a crew that tops the tank up between units is spending water the job never logged. Where a meter cannot be fitted, log refills as a separate column rather than reporting a consumption figure built from them.
Separate the rinse from the heated stage, and read them apart
Most exterior sequences draw at two very different rates, and an average hides both. A pre-rinse on a salted hull side moves volume quickly over a large flat area, and it rarely lifts marine growth or cured salt film on its own; it moves material off the surface so the next stage can work on it. A heated stage, steam or hot water, is the stage that acts on films and deposits and generally holds the greater demand on the machine itself. The final rinse or squeegee pass is the finish that decides whether the area is accepted.
Metering the stages apart is what exposes the waste. If the pre-rinse is running long on units that are already clean, or the final rinse is being repeated because the crew has no written accept criterion, the job is spending water on a decision nobody wrote down. A single blended total can never show that. A stage-level record shows which part of the sequence needs a technique change and which part needs a standard.
Where the water goes is part of the figure
On a floating vessel, anything applied above the waterline ends up at the waterline. On a hardstand, it follows whatever falls, scuppers and drains the yard provides, and on some berths it reaches the water anyway. The site's own rules decide what may be collected, where wash-down is allowed, and whether a wash that leaves an area must be caught before it leaves the berth. Those constraints come from the yard or marina, not from an equipment supplier; they have to be read at the site and asked in writing before the trial is scheduled.
Practically, that means the water-use assessment includes an outlet path per unit: does the run-off drop to the hull base and then to the water, does it track along the toe rail and then either into a deck drain or overboard, and is any containment or matting laid for the units nearest the waterline. Recording the outlet path next to the volume is what lets the two figures be discussed together instead of in two separate arguments.
Afloat and ashore are different trial grounds
Afloat, the machine sits on a pontoon or a berth, and the crew works around rigging, stanchions, through-fittings and the handrail at the edge. A hose or cable that crosses the toe rail is a hazard as well as an obstacle. Power for the machine may be pedestal-supplied, or the unit may be self-contained on the vessel's own supply, and the answer changes both the route and the reading.
Ashore, the crew works on a hardstand or in a lifting cradle with a ladder and a working platform, the supply runs from a yard draw-off, and run-off is governed by the yard's drainage and housekeeping rules. The surface condition also differs: a hull out of the water has been drying, and a hull afloat has been wetted and salted continuously. A consumption figure measured on one ground should never be quoted against the other, because the trial is not comparable in either the surface state or the drainage.
What supply water changes in the assessment
Marina supply is treated water on a shared connection, and the connection itself becomes part of the trial: fitting type, whether an adapter is needed, how long a run has to be laid, and whether the pedestal is shared with a neighbouring berth at the same hour. Draw-off at a yard is often harder and can carry more dissolved solids, and hardness leaves a residue where a wetted surface is allowed to dry; what the supply water demands of the machine across a working season is a separate consideration for the site, not something to settle during a trial.
Temperature and pressure at the draw-off also shift the picture. Cold supply puts more load on the heating stage, so the heated stage may need more time or more attention for the same finish. Where a unit's output is judged against a result rather than a specification, a change in supply conditions is a change in the trial and has to be recorded as one. The practical consequence is small but strict: note supply hardness, supply temperature and the draw-off used alongside the consumption figure, or the figure cannot be repeated.
Deposit type and surface state decide the pass count
Water use tracks the pass count more closely than it tracks area, and the pass count belongs to the deposit. Salt film on topsides, diesel and soot streaking at the transom, growth at the waterline and in the anchor chain run, and organic staining on a non-skid deck are all different problems. They sit on different materials — gelcoat, antifouling, anodised metal, varnish, painted surfaces, non-skid — and each of those boundaries has to be agreed with the owner before anyone applies a heated stage to it, because a finish that tolerates one method may not tolerate another. The site's cleaning pages describe work on vehicle-type surfaces and facility duties; they do not describe a marine duty, and that distinction is the reason a vessel trial earns its own evidence rather than inheriting a figure.
The assessment therefore records, for each unit, what was on the surface, what method was used against it, how many passes that took, and what the volume was. Deposit type becomes the explanation column beside every consumption figure.
A crew record that can be audited
Five columns carry the assessment. Unit of work, as the place named above. Stage — pre-rinse, heated, final rinse. Supply point and its readings, meter or refill count. Outlet path for that unit. And the accept result: whether the unit passed on the first pass, was revisited, or failed and was repeated, with the reason in a word. That last column is the one that turns a consumption log into an assessment, because it attributes water to outcomes rather than to effort.
With those columns filled on a handful of comparable units, a crew can say where the volume is going and can act on it: the pre-rinse that runs long on already-clean panels, the units revisited because the light at that hour made the finish impossible to judge, the waterline units where the outlet path forces a slower method. Without them the crew has an invoice and an argument.
Questions for the supplier, set beside your own measurements
Supplier answers become useful only when they are placed against figures you measured on your own ground. The questions worth asking are specific to this assessment. Which mode, steam or hot water, does the supplier expect to carry the salt-film stage, and what does that mode demand of the supply line at the working position? How is that mode's supply water demand stated — per operating hour of the machine, or per pass over a defined area — and can the answer be checked with an in-line meter at the pedestal? What does the supplier say about supply hardness and residue on a wetted surface that is allowed to dry? Which materials on the owner's surface schedule the supplier will not put a heated stage against, and in what words? And what on a vessel trial, as opposed to a hardstand or a vehicle bay, is outside the supplier's stated range?
An equipment supplier working on the low-water steam cleaning equipment range can answer these in mode and connection terms. A supplier who answers only in generalities has not looked at your record, and neither side can settle a figure on that basis. Where a site's duty sits outside the published range, the supplier's answer is a build question — the customized steam cleaning equipment route exists for cases where the standard configuration and the site do not match — and the vessel trial remains the evidence.
Failure modes that inflate the figure without showing on the meter
Five patterns account for most of the over-consumption on marine work. A crew cleaning to a vague brief repeats units because nobody agreed what finish counts. A stage run at the wrong point in the sequence — a heated stage against a surface still carrying loose material — wastes the pass and the volume with it. A supply hose left running while the operator repositions is unmeasured water that lands on the same bill. A trial ground chosen for convenience rather than representativeness produces a figure that nobody believes, so the work gets re-scheduled and re-run. And a figure quoted across grounds — hardstand measured, afloat promised — collapses the moment the vessel is measured afloat.
Each of those is fixed by the record rather than by the machine: named units, stage-level readings, a shut-off habit, a stated trial ground, and a refusal to move a figure between afloat and ashore.
