How much water did your house use last January? Most of us couldn't guess within a few thousand gallons. Thornton tracks it closely, because that number does more work on your utility bill than your sprinklers do in July.
All 494 homes in Willow Bend, the Lennar neighborhood at the northwest corner of Holly Street and 144th Avenue, get water and sewer service from the City of Thornton. The Willow Bend Metropolitan District took over the old HOA's jobs on January 1, 2026: the open space, the stormwater detention pond, covenant enforcement and architectural review. Your water bill isn't one of those jobs. The city's rules decide what you pay, and the window those rules use to measure your household opens with the November billing period.
Four months that set your baseline for the year
Thornton calls it Average Winter Consumption, or AWC. The city's water rate ordinance builds it from the billing periods covering November through February. It adds up the water used in that stretch, divides by the number of days, and multiplies by 30.42 to get a monthly figure. The city recalculates it once a year.
The reasoning is simple. In a Colorado winter, almost nothing gets watered outside, so what a home uses from November to February is a good read on its indoor needs: showers, laundry, dishes, toilets.
That one figure then does two separate jobs on your bill:
- It sets your Tier 1 allowance. Indoor water up to your AWC is billed at the lowest rate.
- It sets your sewer quantity charge. Under Thornton's sewer ordinance, a home's sewer bill is a fixed monthly service charge plus a quantity charge based on AWC.
So your sewer charge isn't based on the water you use each month. It rests on the winter number, whatever happens in June.
How the tiers stack on top of that number
These are the 2026 rates for a single-family home inside city limits, from Thornton's published rate schedule.
| Tier | What it covers | 2026 rate |
|---|---|---|
| Monthly service charge | Per connection, whatever you use | $10.97 |
| Tier 1 | Indoor use up to your AWC | $7.76 per 1,000 gallons |
| Tier 2 | Outdoor use up to your Monthly Outdoor Allowance | $7.76 per 1,000 gallons |
| Tier 3 | The next 20,000 gallons | $11.64 per 1,000 gallons |
| Tier 4 | Everything above that | $23.29 per 1,000 gallons |
The Monthly Outdoor Allowance, or MOA, comes from your lot size. Thornton gets that from Adams County land valuation records, which list acreage, and converts it to square feet. The lot-size table in the city's 2026 billing fact sheet gives every lot up to 9,000 square feet the same 16,000 gallons a month. After that it rises: 18,000 gallons for lots of 9,001 to 10,000 square feet, 20,000 for 10,001 to 11,000, and up to 80,000 for lots over 43,000 square feet.
Every tier line sits on top of your AWC. Tier 3 starts once you've used your AWC plus your MOA, and Tier 4 starts 20,000 gallons after that.
What the winter number does to a July bill
Take a home on a lot of 9,000 square feet or less, so its outdoor allowance is 16,000 gallons. Say its winter average works out to 4,000 gallons a month. In summer, its first 20,000 gallons each month bill at $7.76 per thousand. Tier 3 begins at 20,001 gallons, and Tier 4 begins after 40,000.
Now give the same house a winter average of 2,000 gallons. Every line moves down 2,000 gallons. Tier 3 starts at 18,001 and Tier 4 after 38,000.
At 2026 rates, each 1,000 gallons of winter average that moves the Tier 3 line is worth $3.88 in any month you cross it. That's the gap between $7.76 and $11.64. Near the Tier 4 line the gap grows to $15.53 per thousand gallons. These are small amounts on any one bill. They also come back every summer month, all year long.
The city's own sample bill shows how a peak month adds up. A household with an AWC of 2,470 gallons used 40,000 gallons in one billing cycle. That ran through all four tiers and came to $422.73 in water charges, before sewer, trash and stormwater.
A January leak is counted all year
The winter average works the other way too. The formula can't tell a family's showers from a toilet flapper that runs all night. Every gallon in those November through February billing periods goes into the average. That average then sets your sewer quantity charge for the months that follow.
This is why Thornton keeps pointing customers to WaterSmart, its online usage tool. In this year's drought update, the city credited WaterSmart with helping residents catch leaks quickly and save money. A leak in May shows up on one bill. A leak in January can also raise the sewer number that sticks around after it's fixed.
The city's watering guide also asks households to wind down and winterize sprinkler systems in October as temperatures drop. If a zone was missed, any water it uses during the November through February billing periods counts toward the average.
Homes without a winter on record
Willow Bend's homes went up between 2019 and 2024. Accounts change hands and new ones open, so some households start a year with no winter history.
The ordinances cover this. When an AWC can't be established, or doesn't reflect actual use, the city uses the class average for the same meter size until an AWC can be set. A household of two and a household of six on the same meter size start from the same assumed baseline. Once the household has a full winter on record, its own number takes over.
The other winter measurement Thornton is waiting on
While Thornton measures each home's winter use, it's also watching the mountains.
Thornton has been under Stage 1 drought restrictions since March 15, 2026, after record-low snowpack in the upper South Platte and Clear Creek watersheds. In its September 15 drought update, Thornton Water said customers had cut use by 10% compared with 2025 as of mid-August. That's about 537 million gallons saved. Raw water storage still stood at only 73% at the end of August. Peak streamflow on Clear Creek stayed under 300 cubic feet per second, against an average above 800, which is close to the 2002 record low.
The utility said Front Range providers need average to above-average snowpack this winter to start recovering. It also said Thornton may move to Stage 2 if conditions get worse over the winter. For now, the Stage 1 rules allow lawn watering two days a week, with no lawn watering between 10 a.m. and 6 p.m. Trees, shrubs, perennials, annuals and vegetable gardens can be watered any day as needed.
The longer-term fix is the Thornton Water Project, a 70-mile pipeline that will bring Cache la Poudre River water Thornton bought in the 1980s. As of September, it was expected to be running by 2028. The city's proposed 2027 Water Fund capital plan sets aside $5,459,471 for the project in 2027 and $37,973,566 across 2027 through 2031.
Where 2027 rates stand
Rates went up this year too. Thornton's February 2026 financial report puts the increases at 11% for water and 6% for sewer. In its January explainer, Thornton Water tied the increase to maintaining and upgrading reservoirs, treatment plants, pipes, pump stations, storage tanks and hydrants, plus PFAS testing and treatment.
For 2027, City Council held first readings on October 27 of ordinances replacing the current water, sewer and stormwater rate schedules. Those are proposals until the council adopts them, and the new dollar figures will be on the city's ordinance page once it does. Whatever the per-gallon rates turn out to be, the winter average decides how many of your gallons fall in the lowest tier.
This post explains how Thornton's published rules work. It's general information, not legal, tax or financial advice, so check your own account and bill with Thornton Water or the right professional.
If you'd like a second set of eyes on what your utility bills mean for the cost of owning your Willow Bend home, Jackie Roacho is happy to sit down and go through the numbers with you. Schedule a free consultation and bring a recent bill.
