Bottled water is typically more expensive than municipal tap water, but consuming the latter is sometimes not an option due to contamination issues. One solution to this problem is to clean tap water prior to consumption with the help of a residential water filter, but even that option can sometimes come at a substantial additional cost.
Is it possible to reduce these drinking water expenses?
The Price of Clean Water
According to recent studies from 2016, the U.S. bottled water industry has become a $14.7 billion market – and is still growing. 1 gallon of bottled water costs as much as $9.50 (estimated based on single servings priced at an average of $1.25 each). Buying in bulk and disregarding quality, costs can get as low as $1.00 per gallon.
In contrast, 1 gallon of municipal tap water is priced at roughly $0.005. However, in many cases tap water needs additional treatment prior to consumption to avoid potential health risks posed by pollutants, such as lead, nitrate, pathogens, and a range of disinfecting byproducts.
Residential Water Treatment Technologies
Residential tap water treatment can be conducted through a range of different technologies to ensure contaminant removal. The most common technologies are:
- Carbon filtration, which removes contaminants via chemical adsorption.
- Reverse osmosis filtration, which uses a semipermeable membrane that allows water molecules to pass through, but rejects up to 99% of all contaminants.
- Distillation, which utilizes heat to vaporize water. The purified water then condenses back to its liquid form in a cooling coil.
Cost Savings with Residential Tap Water Treatment
Using these technologies, is it possible to reduce costs by safely replacing bottled water with municipal tap water?
The different cost factors for residential tap water treatment are filter:
- Installation (if applicable)
1. Acquisition Costs
Acquisition costs listed below are rough estimates and can vary from product to product:
- Carbon filters: $25 - $60
- Reverse osmosis systems: $140 - $500
- Water distillers: $75 - $240
2. Installation Costs
- Carbon filters: No installation required
- Reverse osmosis systems: $100 - $300
- Water distillers: No installation required
3. Operation Costs
- Carbon filters: No operation costs
- Reverse osmosis systems: No operation costs (unless system applies an additional pump)
- Water distillers: 4 hours * 0.7 kW * 0.13 $/kWh = $0.36 per gallon
4. Maintenance Costs
Costs are rough estimates and depend on system specifications.
- Carbon filters: $30 - $130 annually
- Reverse osmosis systems: $60 - $200 annually
- Water distillers: No maintenance costs
Case Study Calculations
1) Single-person household using a reverse osmosis system
For the first example, we assume that a person living in a single household consumes 0.55 gallons of water per day and decides to buy a reverse osmosis filter system. This system comes with costs for acquisition and installation totaling $450, and additional maintenance costs of $100 per year. The price for 1 gallon of bottled water is $2.00.
- Bottled water costs: 2.00 $/gallon * 0.55 gallons/day * 365 days = $401.50
- Treated tap water costs: 0.005 $/gallon * 0.55 gallons/day * 365 days = $1.00
- Additional costs: $450 initial costs + $100 maintenance costs = $550
- Savings: $401.50 bottled water costs - ($1.00 treated tap water costs + $550.00 additional costs) = -$149.50
- Savings: $401.50 bottled water costs - ($1.00 treated tap water costs + $100.00 maintenance costs)= $300.50
Making the switch to treated tap water will increase costs by $149.50 in the first year. For each subsequent year, costs decline by $300.50. Therefore, it takes less than 2 years to cover the initial system costs for a single-person household.
2) 4-person household using a carbon filter
This case study assumes that a 4-person household requires 2.2 gallons of drinking water per day. The example family decides to buy a countertop carbon filter for $60 with yearly maintenance costs of $80; their water savings calculation is as follows:
- Bottled water costs: 2.00 $/gallon * 2.2 gallons/day * 365 days = $1606.00
- Treated tap water costs: 0.005 $/gallon * 2.2 gallons/day * 365 days = $4.02
- Additional costs: $60 initial costs + $80 maintenance costs = $140
- Savings: $1,606.00 bottled water costs - ($4.02 treated tap water costs + $140.00 additional costs) = $1461.98
The carbon filter will help the 4-person household to save $1461.98 in the first year.
Cost Saving Opportunities
As illustrated above, it is possible to save money by drinking treated tap water instead of its bottled alternative. Total savings depend on how much water is being consumed on a daily basis and the treatment technology selected, but can generally present a more cost-effective alternative to bottled water options.
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