Plan the project in five steps
- Ask. Write one clear question, for example: "How can our class use 20% less water?"
- Measure. Find out how much water is used now. Use a bucket, a measuring jug or the water meter. Write numbers with units.
- Find the biggest waste. Draw a bar chart. The tallest bar or a leak is where to begin.
- Act. Choose one to three small changes. Do them for a few days.
- Check. Measure again the same way. Compare before and after. Share what you learned.
Working as a team helps. One person measures, one writes, one checks the sums, one tells the class.
Measure daily use
Easy ways to measure:
- Bucket test: catch the water from a tap or shower in a 10-litre bucket and count buckets.
- Water meter: read it at the same time on two days. The difference (usually in m³) is the use. 1 m³ = 1,000 litres.
- Diary: list each use (shower, toilet, washing clothes, cooking and drinking, garden) with litres.
In the 3D, the example numbers are 45 L (shower), 35 L (toilet), 25 L (clothes), 15 L (cooking and drinking), 20 L (garden) and 10 L (leaks): 150 litres per person per day. Your home will be different. That is why we measure.
Find leaks and use water efficiently
A leak is water that works for nobody. A drop is about 0.07 mL. If a tap drips once every second, that is 86,400 drops in a day, which is about 6 litres a day or about 180 litres a month. A thin stream wastes far more.
To find leaks, turn off every tap and look at the meter. If the number still moves, there is a hidden leak. Also look for dripping taps, running toilets and wet patches.
Efficient habits:
- Shorter showers and a bucket bath save a lot.
- Turn the tap off while brushing.
- Water the garden with rain or used water, in the cool part of the day.
- On farms, use drip or sprinkler irrigation instead of letting water run over the field.
Catch rain
Rainwater harvesting means collecting rain from a roof into a tank, barrel or pit.
Quick sum: 1 mm of rain on 1 m² is 1 litre. So a 30 m² roof in 50 mm of rain receives 30 × 50 = 1,500 litres. In real life you catch about 80% (some splashes and evaporates), so about 1,200 litres.
Keep the roof and gutter clean, put a mesh over the barrel mouth, and cover it so mosquitoes cannot breed. Use this water for the garden, cleaning and toilets, and drink it only if it has been treated.
Extra rain can also be led into a pit or a pond to refill the groundwater.
Check results and share
After the habits have run for a few days, measure again in the same way. Work out the saving:
Saving % = (before − after) ÷ before × 100
In the 3D, a shorter shower (saves 15 L), fixed leaks (saves 10 L) and garden watered with rain or used water (saves 15 L) cut 150 L to 110 L. That saves 40 L, which is about 27%. For a family of 4, that is 40 × 4 × 30 = 4,800 litres a month.
Be honest. If the weather, number of people or days changed, say so. Then share a short poster or talk with your numbers.
Try it: a seven-day water diary
For one week, count the buckets for each use at home and write them in a table. On day 4 start one new habit. At the end, draw two bars: average litres per day before and after. Did you hit your target?
Key formulas and definitions
- 1 mm of rain on 1 m² = 1 litre
- Rain collected (L) = roof area (m²) × rain (mm) × share caught
- Leak (L/day) = drips per second × 0.07 mL × 86,400 ÷ 1,000 ≈ 6 × drips per second
- Saving % = (before − after) ÷ before × 100
- Use per person per day = total litres ÷ (people × days)
- 1 m³ = 1,000 litres
Worked examples
1. A tap drips 3 times every second. About how many litres does it waste in a day and in a month (30 days)?
About 6 L a day for each drip per second, so 3 × 6 = 18 L a day. In 30 days: 18 × 30 = 540 L.
2. A 40 m² roof gets 25 mm of rain. How much water falls on it, and how much is caught if 80% is caught?
Fallen = 40 × 25 = 1,000 L. Caught = 0.8 × 1,000 = 800 L.
3. A person cuts daily use from 150 L to 110 L. What is the percentage saving?
(150 − 110) ÷ 150 × 100 = 40 ÷ 150 × 100 = 26.7%, about 27%.
4. A family of 5 saves 15 L each per day by taking shorter showers. How much is saved in 30 days?
5 × 15 = 75 L a day. 75 × 30 = 2,250 L.
5. A barrel holds 1,200 L of rain. The garden uses 80 L a day from it. How many days does the barrel last?
1,200 ÷ 80 = 15 days.
6. A water meter reads 1,250.4 m³ on Monday and 1,252.9 m³ five days later. Five people live in the house. Find the use per person per day.
Used = 1,252.9 − 1,250.4 = 2.5 m³ = 2,500 L. Per person per day = 2,500 ÷ (5 × 5) = 100 L.
Common mistakes
- Taking only one measurement and calling it a result. Measure before and after, in the same way.
- Forgetting units. Always write L, mm, m² or m³.
- Thinking a small drip is not worth fixing. 1 drip per second is about 6 litres a day.
- Assuming all rain on a roof is caught. Some is lost, so use about 80%.
- Drinking collected rain water without treating it.