Refill Stations or Bottled Water?
Lincoln Primary School uses about 720 plastic water bottles per week, 500 mL each, bought through a vending contract at $0.35 per bottle. The contract runs three more years. A parent group proposes two filtered refill stations at $4,800 each, with filters costing $600 per station per year; the stations should last eight years. They estimate each station would serve 300 refills per week. A rival proposal is to give every one of the 480 students a reusable bottle at $6 each. The school's waste audit found bottles are 22% of landfill waste by weight. The principal wants a recommendation covering cost, waste, and whether families will actually use the stations.
1. Calculate the three-year cost of the refill-station option (installation plus filters) and compare it with three years of bottled water. Show your work.
Read the worked answer
Bottled water, 3 years:
- 720 bottles/week × 52 weeks = 37,440 bottles/year
- 37,440 × $0.35 = $13,104 per year
- $13,104 × 3 = $39,312
Refill stations, 3 years:
- Installation: 2 × $4,800 = $9,600
- Filters: 2 × $600 × 3 = $3,600
- Total = $13,200
So the stations save roughly $26,100 over three years while the contract runs. Over the full eight-year life the gap widens: about $19,200 for stations versus about $104,800 for bottles.
Caveat: the vending contract has three years left, and leaving it early may carry a penalty that is not in these figures. The recommendation should say the size of that penalty decides whether switching now or at contract end is cheaper.
2. The waste audit says bottles are 22% of landfill waste by weight. Explain why that figure alone does not tell the principal how much the stations would cut waste, and name one more piece of data needed.
Read the worked answer
A weight percentage does not translate directly into a change in what gets thrown away.
- Bottles are light but bulky, so by weight they may be 22% while taking up a much larger share of the bin by volume. Cutting them changes bin space and pickup frequency differently than 22% suggests.
- The audit does not say whether those bottles are the school's 720 per week, or bottles brought from home. Stations only replace bottles bought and drunk at school.
- If some bottles are already recycled, removing them from landfill is a smaller gain than 22% implies.
Data needed: the count (or volume) of bottles in the school's waste per week, and how many of those come from the vending contract. That converts the weight figure into a predicted change the principal can check after a trial.
3. Identify one non-financial risk of the refill-station plan and describe a low-cost way to test it before the school commits.
Read the worked answer
Risk: families may not use the stations. The $600-per-week refill estimate is a guess; if students arrive with bottles already filled, or distrust the taste, the school pays $9,600 for equipment that replaces few bottles. Filters also need changing on schedule - a neglected station defeats the purpose.
Test: run a four-week pilot with one rented or borrowed station in the busiest corridor and a tally counter or simple sign-in sheet. Compare refills per week against the 300 estimate, and repeat the waste count in week four to see whether bottle volume in bins actually falls.
That pilot costs far less than the full installation and gives the principal real usage numbers, plus a sense of how often filters need attention, before committing the rest of the money.