Use one scope and one time horizon
A fair cost comparison starts with systems intended to solve the same documented problem. Comparing a jug with a whole-house treatment train is meaningless unless the reader first defines the outlet, flow and outcome.
Choose a time horizon, record the price date and keep taxes, delivery and installation treatment consistent.
Cost inventory
Purchase and installation
Include equipment, adapters, housings, valves, dedicated taps, drain work, electrical work, commissioning and any pre-treatment required for the main system to operate within its conditions.
Consumables
List every cartridge, membrane, media charge, UV lamp, sleeve, salt or sanitising item by exact part number. Record whether the replacement trigger is time, volume, measured condition or “whichever comes first.”
Water and energy
Record metered-water assumptions for regeneration or reject water and electricity assumptions for pumps, UV equipment or boiling-water functions. Use a dated tariff and show sensitivity rather than promising one household bill.
Service and verification
Include professional service, cleaning, sanitisation, repair allowance and any suitable follow-up testing. DWI says preventive maintenance is preferable to waiting for failure and that manufacturer instructions are a minimum requirement.[5]
Build the five-year worksheet
For year y:
annual cost(y) = scheduled parts + water + energy + service + planned verification
Then:
five-year ownership = purchase + installation + Σ annual cost(y)
The worksheet must expose every input. It must not auto-fill a replacement interval, tariff, reject-water rate or service cost from memory.
Separate known, estimated and unknown
Use three labels:
- Known: current quoted price or exact published requirement, with date and source.
- Estimate: a transparent assumption used for comparison.
- Unknown: not stated or not yet verified.
An unknown does not become zero. Show a range or leave the total incomplete when the missing item could change the decision.
Maintenance record
Keep installation date, model and serial details, exact part numbers, completed work, alarm events, observed condition and verification results. DWI recommends keeping management and maintenance records for treatment systems in the private-supply context.[5]
DWI also warns domestic filter owners to follow cleaning and cartridge-change instructions.[3]
Compare quotes without false precision
A five-year total is a planning estimate. Prices, tariffs, water use and service needs change. Round sensibly, show the price checkpoint, and avoid implying that a calculated penny is a measured future cost.
Repeat purchase is not recurring commission
Filters, media and lamps may be bought again. That does not mean an affiliate receives recurring commission. Home Water Blueprint has no active affiliate links, and commercial availability must not determine the maintenance schedule or comparison result.
Next steps
- Whole-house cost inputs →
/whole-house-treatment/ - RO and cartridge schedule →
/drinking-water-systems/ - Softener salt/service inputs →
/hard-water-softening/ - UV lamp and verification inputs →
/uv-water-treatment/ - Tap, shower and leak products →
/taps-showers-leaks/