Hot Water for Labour Accommodation: Sizing Guide

Labour accommodation is the most demanding hot water load most contractors will ever specify, and it is routinely sized as though it were a large apartment block. It is not. The total daily volume is often modest compared with a hotel of similar headcount, yet camps run out of hot water far more often.

The reason is not volume. It is simultaneity. In a hotel, guests wake and shower across three or four hours. In labour accommodation, the buses arrive together and several hundred men shower inside a single ninety-minute window. A system sized on daily totals will be undersized by a factor of three or more when it matters, and the complaint arrives on the first working day.

This guide sets out how to size it properly: litres per worker derived rather than assumed, the peak that actually governs the design, how shift rosters change the answer, and where to spend the budget between storage and heating power.

How Much Hot Water Does One Worker Actually Use?

Most published figures for worker accommodation are quoted without derivation, which makes them impossible to check or adapt. Here is the arithmetic instead.

A shower delivers mixed water at roughly 40 °C. Your system stores hot water at 60 °C. Those are different quantities, and confusing them is the single most common sizing error in this sector. The proportion of stored hot water in a mixed shower is:

Hot fraction = (shower temperature − cold inlet) ÷ (storage temperature − cold inlet)

With a 25 °C cold inlet, which is realistic for the Gulf across most of the year, that is (40 − 25) ÷ (60 − 25) = 0.43. So a shower consumes only about 43 per cent of its total flow from your hot water system.

Add an allowance for washbasins, ablution and personal laundry, and 30 litres of stored hot water per worker per day is a defensible design figure for a single-shower-per-day population. Raise it for hot, dusty site work where two showers a day are normal, and raise it again if the camp does laundry centrally rather than by hand.

Note what this figure is not. It is not a peak-hour rate, and it is not the number you size heater capacity on. It is only the starting point.

The Simultaneous Peak Is the Whole Design Problem

Every commercial building has a peak, and sizing on peak rather than on daily total is the general principle we set out in our guide to commercial hot water systems. What makes labour accommodation different is how sharp that peak is.

In hospitality, demand spreads because guests choose their own schedule. In a camp, nobody chooses. Transport returns at a fixed time, shifts end together, and prayer times and meal service concentrate the rest. A realistic planning assumption is that 60 to 75 per cent of the entire day’s hot water is drawn inside ninety minutes, and in single-shift camps with one bus arrival it can be higher still.

Compare the two profiles for the same 200 people:

This is why a camp can have a smaller daily demand than a hotel and still need more installed capacity. Size on the ninety minutes, not the twenty-four hours.

Shift Patterns Are a Free Design Lever

This is the one variable available to you here that is available nowhere else in commercial hot water, and it costs nothing to use.

If a camp runs a single shift, the entire population peaks at once and the system must be built for that. If it runs two shifts separated by several hours, the same population produces two peaks of half the size, and the tank recharges in between. The equipment required falls accordingly.

Before finalising any specification, ask the operator for the actual roster, not the headcount. A camp of 400 on staggered shifts can need less installed capacity than a camp of 250 on one. Where rosters are still being decided, this is worth raising with the client early, because a decision that costs the operator nothing can remove a substantial line from the mechanical budget.

Storage or Recovery: Where to Spend the Money

Once you know the peak, you have two ways to meet it, and the choice is a genuine capital trade-off rather than a right answer.

• Storage-led. Hold the whole peak in tanks and reheat afterwards at leisure. Lower heating power, lower electrical demand charges and smaller cabling, but more tank volume, more plant room space and more standing heat loss.
• Recovery-led. Smaller tanks with high heating power that keeps up during the draw. Less space and less standing loss, but a much higher connected load, heavier supply cabling and a larger demand charge every month.

In practice the sensible design is a blend, and the blend is where an experienced supplier earns their fee. The table in the worked example below shows exactly how the two trade against each other in kilowatts and litres.

Worked Example: A 200-Worker Camp

Assumptions stated openly so you can substitute your own: 200 workers, 30 litres each per day at 60 °C, 25 °C cold inlet, single shift, 70 per cent of the day’s volume drawn in a ninety-minute window.

• Daily hot water: 200 × 30 = 6,000 litres
• Daily energy: 6,000 × 35 × 0.00116 = 243.6 kWh
• Peak-window volume: 70 per cent of 6,000 = 4,200 litres in 90 minutes
• Peak-window energy: 170.5 kWh delivered in 1.5 hours

That last figure is the design load. Meeting it entirely from live heating would require about 114 kW. Meeting it entirely from storage would require 4,200 litres of usable hot volume. Everything sensible sits between those two poles:

Two points are worth drawing out. First, usable volume is not tank volume: draw-off mixes incoming cold with stored hot, so plan on using roughly 75 to 80 per cent of nominal capacity before delivery temperature falls. Second, run the same calculation for a two-shift roster and the peak volume halves to 2,100 litres, which moves every row of that table down by half. Our central systems are manufactured from 100 to 7,500 litres precisely so this can be matched rather than approximated, and the general sizing method behind it is covered in our guide to what size water heater you need.

Distribution: Ring Mains and Dead Legs

Accommodation blocks are long and low, which puts the ablution facilities a considerable distance from the plant room. That geometry creates a problem sizing calculations never reveal.

A dead leg is a length of pipe with no circulation. Water sits in it, cools, and the next user runs it to waste while waiting for hot. Multiply that by several hundred showers a day and it becomes a measurable loss of water, of time, and of the peak capacity you just paid for, because water discarded down the drain was still heated.

The answer is a properly insulated recirculating ring main with a return leg and a circulation pump, so hot water is always present near the outlets. Insulate the return as well as the flow, because an uninsulated return quietly heats the corridor instead of the water. Where blocks are widely separated, decentralised plant serving each block often beats one central plant with long distribution runs, and that judgement belongs at design stage rather than after commissioning. Our overview of central water heating systems covers the central-versus-local decision in more detail.

Temperature, Scalding and Hygiene

Shared ablution blocks concentrate risk, and the standard practice here is not complicated but it is frequently skipped.

• Store hot. Keeping storage at 60 °C or above suppresses bacterial growth, and a stored temperature dropped to save energy is a false economy.
• Distribute hot. Circulation should not be allowed to fall below roughly 50 °C anywhere in the ring main, including at the far end.
• Deliver safe. Water at 60 °C scalds. Outlet temperature is brought down at the point of use with thermostatic mixing valves, not by lowering the stored temperature.

The mistake to avoid is solving scalding by turning the tank down. That creates a hygiene problem to fix a safety problem, when correctly specified mixing valves solve the safety problem without touching storage temperature at all.

Why Uptime Means Something Different Here

Redundancy in commercial hot water is a familiar subject, and the case for cascaded units rather than one large one is set out on our commercial systems page. What changes in labour accommodation is the consequence of getting it wrong.

A hotel with a failed heater can move guests, refund nights and buy time. A camp cannot. The residents have nowhere else to go, the failure affects every one of them simultaneously, and it lands on the operator as a welfare and compliance issue rather than a commercial one. Sites are also frequently remote, so a replacement unit may be days away rather than hours.

That argues for multiple smaller units in cascade over a single large one, spare capacity kept on site for critical components, and isolation valves that let one unit be serviced while the rest keep running.

The Strongest Solar Case in Commercial Hot Water

If you read only one section of this guide for its financial impact, read this one.

Solar water heating rewards demand that is large, steady and year-round, and labour accommodation fits that description better than any other sector we supply. Occupancy does not swing with tourist seasons or school holidays, the load runs every day of the year, and the roof area above long single-storey blocks is usually generous and unshaded.

Taking the 200-worker camp above at 243.6 kWh a day:

• Annual hot water energy: 88,914 kWh
• At the Saudi commercial rate of SAR 0.368 per kWh including VAT: SAR 32,720 a year spent on heating water alone
• With solar carrying 60 per cent of it: SAR 19,632 saved per year

That is a recurring operating saving on a facility that will run for the life of the project. Whether it justifies the capital depends on your installed cost, and our guide to solar water heater payback shows how to work that out honestly, including the assumptions suppliers most often inflate. If you are already convinced, sizing the solar array is the next step, and our solar water heaters run to 15,000 litres for installations of this scale.

Water Quality and Maintenance Access

Camps run their equipment harder than almost any other application, so two practical matters deserve attention at design stage rather than after the first failure.

Feed water across much of the region is hard groundwater or aggressive desalinated supply, and both attack storage differently. Scale insulates heating surfaces and quietly destroys efficiency; aggressive water attacks the tank itself. This is why enamel-lined tanks with a sacrificial magnesium anode, and a maintenance routine that actually inspects that anode, matter more here than in a villa. We cover the regional water chemistry in more detail on our page about water heaters in Saudi Arabia.

Leave access. Plant rooms in camps are often built to the minimum footprint that fits the equipment on the drawing, with no allowance for withdrawing an element, lifting a tank lid or replacing an anode. A plant room that cannot be maintained will not be maintained.

Six Mistakes We See Repeatedly

1. Sizing on daily total. The daily figure is an input to the peak calculation, not a specification.
2. Confusing mixed water with hot water. A 48-litre shower draws about 21 litres from storage, and treating those as the same number oversizes tanks while undersizing nothing useful.
3. Ignoring the roster. Shift patterns can halve the required equipment and cost nothing to ask about.
4. Long uninsulated runs with no return. Capacity paid for at the plant room, then discarded down the drain at the block.
5. Lowering storage temperature to prevent scalding. Fit mixing valves instead.
6. One large unit with no redundancy, on a remote site, several days from a replacement.

Frequently Asked Questions

How much hot water per person for labour accommodation?

About 30 litres per worker per day of stored water at 60 °C is a defensible planning figure for one shower a day, derived from a six-minute shower plus an allowance for basins and personal laundry. Increase it for two showers a day in hot outdoor work, or where laundry is done centrally.

Why does a camp run out of hot water when the tank size looks correct?

Almost always because the system was sized on daily volume rather than on the ninety-minute peak, or because usable volume was assumed to equal nominal tank volume. Only around three-quarters of nominal capacity is delivered at temperature before incoming cold dilutes the tank.

Should the system be central or one per block?

It depends on the distance between blocks. Central plant is efficient and simple to maintain when blocks are close together, but long distribution runs lose heat and create dead legs. Widely separated blocks are usually better served locally, each with its own storage.

How many showers should a camp provide per occupant?

Fixture provision ratios are set by the accommodation standard your project is contracted to, and many authorities in the region specify minimum ratios of showers and washbasins per occupant. Confirm the applicable standard first, because fixture count feeds directly into the peak flow your system must sustain.

Is solar or a heat pump better for worker accommodation?

Both suit the load, and they are not exclusive. Solar carries the base load at no fuel cost when roof area is available; a heat pump reduces the cost of the shortfall and works at night and in poor weather. Many camps of this size end up with solar plus a heat pump or electric backup rather than a single technology.

Can capacity be added later if headcount grows?

Yes, if it is planned for. Cascaded units with space, pipework connections and electrical capacity left for an additional module can be extended without disturbing the existing installation. Retrofitting expansion that was never allowed for is far more disruptive and expensive.

Send Us Your Headcount and Roster

Give us occupancy, shift pattern, number and separation of blocks, fixture count per ablution block, and your available roof area, and our engineers will return a sized system: storage volume, heating power, distribution arrangement and, where it makes sense, the solar contribution with the payback calculated from your own tariff.

Every unit is manufactured to ISO 9001:2015 quality management standards. Email sales@eauchauffage.com or call +1 (905) 299-3382. See our full range of commercial water heaters, or read the related guide to hotel hot water systems if your project includes staff and guest accommodation together.