Start with the meter and the service period, not a guessed gallons-per-car benchmark. A useful reconciliation answers three different questions: how much fresh water entered the property, how the utility calculated current charges, and which uses explain that volume. Each question needs its own evidence.
Collect one consistent period
Record the meter reference, the time of both readings, actual or estimated status, unit and any multiplier. Retain the bill pages showing consumption and current charges. Match the wash-count export to those same timestamps. A calendar-month POS report cannot precisely explain a bill spanning different dates without a dated bridge.
Check whether the register already includes fixed zeros or a multiplier before multiplying again. A compound installation can contain more than one register; a replacement or rollover can break a simple subtraction. The tool rejects a declining reading because it cannot determine what changed. Obtain the utility’s explanation and split the period where needed.
| Evidence | Question it answers |
|---|---|
| Dated meter reads and bill | Which meter, service dates, units, estimates and adjustments produced the billed quantity? |
| POS completed-service counts | How many services occurred during those same dates, including member visits and excluding voided counts? |
| Submeter or supported non-wash log | What fresh water went to restrooms, landscape, cleaning or another use? |
| Reclaim-system records | What is measured as recovered flow, makeup water, purge or discharge? Do not add internal circulation to purchased volume. |
| Current tariff and bill detail | Which volume basis, fixed charges, tiers, minimums, credits and rounding rules apply to this account? |
Convert volume without changing its meaning
One HCF is 100 cubic feet. The US liquid gallon is 231 cubic inches, so one cubic foot is 1,728 ÷ 231, about 7.480519 US gallons. This tool uses that physical conversion. NYC DEP’s meter-reading brochure uses the rounded explanations 7.48 gallons per cubic foot and 748 gallons per HCF. Its historical prices are not inputs to this tool.
Preserve the bill’s own quantity and rounding convention when checking charges. A small difference created by physical conversion versus a rounded billing convention is not automatically an overcharge. Ask the utility to explain any whole-unit rounding, estimated usage or rebill before classifying a variance.
Fresh-water volume = (current reading − prior reading) × multiplier × unit conversion
Fresh wash water = metered fresh water − supported non-wash fresh water
Fresh water per completed wash = fresh wash water ÷ completed washes
Modeled charges = billed water HCF × water rate
+ billed sewer HCF × sewer rate + fixed charges + signed adjustments
Charge difference = actual current charges − modeled charges
The ratio is unavailable at zero washes. It does not reveal total water applied by the wash because internally reused water can circulate more than once. The model also cannot separate losses, unmetered uses or inaccurate counts merely by dividing a property-wide meter reading.
A fictional bill with an unexplained eight dollars
The invented meter rises from 120,000 to 132,000 cubic feet over 30 days, with multiplier 1. The difference is 12,000 cubic feet, or 120 HCF and approximately 89,766.234 US gallons. A separately supported 6,000 gallons of non-wash use leaves approximately 83,766.234 fresh wash gallons. At 3,000 completed washes, that is approximately 27.922 fresh gallons per wash. It is an example, not a target or an industry average.
The fictional bill charges 120 HCF at $5 for water and 100 HCF at $8 for sewer, plus $50 fixed charges and a $20 credit. The modeled current charge is $1,430. The entered actual current charge is $1,438, leaving $8 to explain. Those invented flat rates do not quote any New York utility. The different sewer quantity is an explicit fictional bill assumption, not an automatic entitlement to a sewer deduction.
Do not force the eight dollars into a balancing line. Request the missing charge description, confirm whether it belongs to the current period, and assign an owner to resolve it. Prior balances, payments, penalties and deposits should be separated from current service charges before using this comparison. Tiered tariffs, minimum bills and percentage-based sewer calculations need their actual schedules outside this simple model.
Investigate a volume change in a useful order
First check dates, units, estimates and meter changes. Then verify the completed-service count and changes in the mix of services. Compare supported non-wash uses, leak observations, equipment settings and reclaim operating records. Where a leak is suspected, arrange safe inspection with the responsible technician; a spreadsheet cannot locate it.
EPA WaterSense discusses metering and facility-specific evaluation of vehicle-wash water management. Use measured observations and the proposed system’s actual design. A vendor’s reclaim percentage is not the same as a reduction in the utility bill, and neither is a guarantee of the site’s future consumption.
Evaluate a project and keep the permit lane separate
Build a before-and-after case using the actual tariff, supported changes in purchased water and sewer billing, installation and civil work, maintenance, electricity, chemicals, outage timing and residual operating costs. Avoid counting water savings twice or assuming fixed charges disappear. Put payments and downtime in the equipment reserve plan and monthly cash schedule.
Recovery equipment does not establish discharge authorization. New York DEC’s SPDES program and the receiving authority’s requirements need site-specific review. EPA distinguishes direct discharges to water bodies from indirect discharges to municipal treatment works, which use the pretreatment framework. Trace the actual outlet and obtain the relevant written conditions with the environmental adviser.
Download the blank meter and bill evidence log
Continue with the utility cost guide and environmental diligence guide.
Maintain the evidence
The owner or buyer assigns a utility reviewer to the meter log. Check the account’s tariff on each effective-date change and preserve its version with the bill. Revisit the model when meters, billing methods, service mix or reclaim settings change. The website editor reviews this method annually; the tool does not fetch rates.
Questions before using the result
Can I enter gallons directly?
Yes. Select US gallons as the meter reading unit. HCF billed quantities remain separate, and the tool converts the meter volume for comparison.
Does a zero charge difference verify the wash?
No. It only means the entered arithmetic agrees. The readings, bill, service count and operating evidence can still be incomplete or wrong.
Can I assume sewer volume equals fresh-water volume?
Use the actual bill and applicable tariff. Sewer basis, adjustments and approvals require account-specific evidence; the tool accepts a separate billed sewer quantity.
What happens if the meter was replaced?
Do not subtract unrelated registers. Obtain the closing old-meter and opening new-meter records, split the period and reconcile both components outside the single-meter tool.
Connect supported usage costs to contribution
Connect supported usage costs to contribution with the method, private tool and reproducible fictional case. Reconcile periods and amounts before carrying a result into another model.
Connect operating evidence and the next decision
Chemical inventory and usage. Keep periods and definitions consistent when manually carrying results between tools.
Sources and scope
Official and original sources checked October 17, 2026. These sources support the identified rules and methods; they do not verify a particular business or property.
- US Environmental Protection Agency — WaterSense at Work 5.4: Vehicle WashesFacility-specific metering, water management and project evaluation. Not a promised saving, site benchmark or discharge authorization.
- NYC Department of Environmental Protection — How to Read Your Water MeterHistorical meter-reading explanation and rounded CF/HCF conversions only. Its old rates, rollout and contact details are not used.
- National Institute of Standards and Technology — Handbook 44, Appendix C: General Tables of UnitsStable US liquid gallon definition of 231 cubic inches. The model derives 1728/231 gallons per cubic foot.
- NYS Department of Environmental Conservation — SPDES permit programDirect surface/groundwater discharge and permit review; site-specific conditions govern.
- US Environmental Protection Agency — Effluent guidelines implementation and complianceDirect dischargers versus municipal-treatment-system pretreatment.
Continue your review
Verify the revenue · Normalize earnings · Model the cash flow