How much drinking water does your outdoor crew need? A simple site plan
A quick way to work out litres a day, refills and water stations for your site, with a worked example for a 25-worker crew.
From 1 December 2026, a cool drinking water supply near work areas is a requirement under MOM's heat-stress measures. Having a water cooler somewhere on site is not enough: it has to be close, cool and never run dry during the shift.
Here is a simple way to plan it.
What MOM expects
- Cool water close to the work. MOM's FAQ describes this as a short, convenient distance, not more than a 3 to 5 minute walk from work areas.
- Regular drinking. From WBGT 31°C, workers should drink at least 300 ml every hour, and more for heavier work.
- Cool, not just available. Water coolers, chilled dispensers, or drinking water in insulated containers all count.
Step 1: work out litres a day
Use this formula:
Litres a day = workers × shift hours × litres per hour × 1.2
- Litres per hour: about 0.3 L for moderate work and 0.45 L for heavy physical work.
- × 1.2 adds a 20% buffer for hotter days, spills and extra breaks.
Step 2: work out refills and stations
- Refills: divide the litres by the size of your containers (for example 20 L).
- Water stations: at least one per work area that is more than a few minutes' walk from the others, and at least one per 25 workers.
Worked example: 25 workers, heavy work, 10-hour shift
| Item | Calculation | Result |
|---|---|---|
| Litres a day | 25 × 10 × 0.45 × 1.2 | 135 L |
| 20 L refills a day | 135 ÷ 20, rounded up | 7 refills |
| Water stations (2 work areas) | the larger of 2 work areas or 25 ÷ 25 | 2 stations |
Plan who refills them and when. Seven refills spread across a shift is about one every 90 minutes, so make it a named person's task, not "whoever notices".
Tips that make the plan work
- Place stations by work area, not by the site entrance. If the walk is long, workers will skip drinks.
- Keep the water cool. Put stations in the shade, use insulated containers, and top up with ice where possible.
- Schedule water breaks, especially when the WBGT climbs. Thirst comes late; a worker who waits until thirsty is already behind.
- Add electrolytes for long, heavy shifts where workers sweat a lot.
- Check the stations on every WBGT round, so a dry station is spotted within the hour.
How HeatAware helps
The water plan on our kit page does this calculation for you. Enter your crew size, shift hours, work areas and how heavy the work is, and it works out litres a day, refills and stations, then sizes the coolers and cooling kits.
Work out your water plan in Step 2 of the kit page.
Frequently asked questions
Is bottled water enough?
It can be, if it is kept cool and close to the work. Warm bottles left in the sun do not meet the "cool water" expectation.
Does tea or a soft drink count?
Water should be the main drink. Sugary and caffeinated drinks are not a good substitute during heavy work in the heat.
What if work areas move during the day?
Use portable insulated containers that can move with the crew, so the 3 to 5 minute distance still holds.
General guidance based on MOM's FAQs on Heat Stress Measures for Outdoor Work. The formula is a planning estimate; adjust it to your conditions.