Walk a new-construction street in Castle Rock this fall, past the framed-out garages and the meter boxes waiting for hookup, and you're looking at a cost that already got decided before the drywall went up. It has nothing to do with granite or cabinet grade. It's the water fee, and this year the town rewrote the formula for calculating it based on one thing: how big the house is.
That single change is worth understanding before you compare a Castle Rock floor plan to one in Parker or Highlands Ranch, because list prices this year have told a scattered story on their own. Depending on which data source you check, Castle Rock's median has landed anywhere from the mid-$600,000s to the high-$700,000s over recent months, and the sources don't agree with each other closely enough to treat any single number as settled. A separate cost to compare is the fee structure, which now varies by home size: a 1,800-square-foot home and a 6,000-square-foot home fall into different tiers.
How Castle Rock's New Water Fees Work
Every new home built in Castle Rock pays a tap fee to connect to the town's water system. Castle Rock Water director Mark Marlowe told the Colorado Sun this summer that the single-family tap fee runs $45,760, a number set independent of the house's price or the builder's margin. Denver Water, by comparison, hadn't touched its own connection fees since 2013 until this year, when it raised them by as much as 32 percent to catch up on decades of deferred cost. Castle Rock's fee has always been closer to current construction reality, which is part of why the town has spent this year adjusting it further rather than leaving it flat.
That tap fee is separate from the system development fee, and it's the SDF that just got a structural overhaul. Historically, Castle Rock calculated water and wastewater development fees using a flat rate tied to plumbing fixture counts. In April 2026, the Town Council approved a different method entirely: a tiered fee scaled to square footage, built on two years of actual water-use data pulled from homes constructed since the town's 2022 landscaping ordinance took effect.
What the Water-Use Study Actually Found
According to a Castle Rock News Press report, Castle Rock Water studied roughly 750 homes built between 2023 and 2025 and found something that made the old fixture-based fee look imprecise. Water use didn't track cleanly with bathroom counts. It tracked with floor area. Homes between 1,500 and 1,999 square feet averaged about 70 gallons of water per day, while homes between 5,500 and 5,999 square feet averaged about 167 gallons per day, and homes in the 7,000-to-7,499-square-foot range averaged around 185 gallons per day. The overall average across the study was 152 gallons per day.
Marlowe explained the logic to the Castle Rock News Press this way:
"The fact that the water use is going down will have an equal benefit on the amount of infrastructure, the size of infrastructure, the timing of infrastructure. These new homes are just not going to be adding anywhere near the kind of peak demand that we've seen historically."
To translate that into a fee schedule, the utility set its benchmark, called a Single Family Equivalent, at the 75th percentile of home sizes built since 2023, which lands between 5,500 and 6,000 square feet. Homes smaller than that benchmark now pay less. Homes larger than it pay more. Town staff and Mayor Jason Gray framed the change around affordability, with Gray telling reporters that easing costs on smaller homes could help first-time buyers get into the market.
What the Gap Actually Looks Like
Here's where the numbers stop being an abstraction. Under the new tiered schedule, which took effect this summer, stacking the water and wastewater components together comes out, according to Hoodline, to roughly $21,750 for a home under about 2,000 square feet, compared with roughly $59,657 for a home in the 7,500-to-7,999-square-foot range.
| Home Size | Estimated Water/Wastewater SDF |
|---|---|
| Under 2,000 sq ft | ~$21,750 |
| 5,500 to 6,000 sq ft (benchmark) | Set at 1.0x, the reference tier |
| 7,500 to 7,999 sq ft | ~$59,657 |
That's a spread of nearly $38,000 between the small end and the large end of new construction, before either house has a single fixture installed. The Home Builders Association of Metro Denver told the Denver Gazette that total development-related costs on a new single-family home in Castle Rock can already top $100,000, or roughly 15 percent of the home's final price. The tiered water fee doesn't create that burden. It redistributes it, shifting weight away from compact homes and onto larger ones.
Town staff projected the overhaul would reduce overall system development fee revenue from single-family construction by about 10 percent, or roughly $4 million, in the near term. For builders working smaller floor plans, that's real headroom. For builders working the upper end of the size range, it's a cost that shows up in the price tag whether the buyer sees the line item or not.
Why the Fee Exists in the First Place
None of this happens in a vacuum. Castle Rock runs its own water utility rather than buying from Denver Water, largely because the town sits outside the natural flow of Colorado's mountain-fed rivers. Historically, most of its supply came from the Denver Basin aquifers, deep nonrenewable groundwater that the town has been drawing down for decades through 63 wells ranging between 500 and 2,500 feet. As of 2025, only about a third of the town's water came from renewable sources, a mix of local surface water from Plum Creek, imported water through the regional WISE partnership, and reused water.
The Plum Creek Water Purification Facility, completed in 2013 and now being expanded from 6 million to 12 million gallons a day of capacity, is the piece of infrastructure doing the work of that transition. Castle Rock has also become the largest single owner of WISE supplies among participating providers, and this year the town began a new pipeline project connecting Plum Creek to the Rueter-Hess Reservoir for storage, backed in part by a $1.75 million federal grant. The goal, according to the town's own water resources plan, is a fully renewable supply by 2065.
None of that is free, and it's the reason Castle Rock Water announced a separate $500 million, decade-long capital plan on January 1, 2026, alongside a roughly $4 per month increase to average residential bills starting on February 2026 statements, with projected annual increases of 4.5 to 5 percent over the following five years. That's the cost existing homeowners carry. The tiered SDF is the cost new construction carries instead, distributed by square footage rather than by monthly usage.
Before You Compare Floor Plans
If you're weighing a new build in Castle Rock against a comparable listing in a neighboring South Metro town, the size of the house is no longer just a lifestyle decision about how much room you need. It's a line item that moves independently of the sale price, in a direction (larger home, larger fee) worth including in your cost comparison.
A few questions worth asking a builder or the town directly before you commit:
- Which system development fee tier does this specific floor plan fall into, and is that fee included in the base price or added at closing?
- Is the lot served by Castle Rock Water directly, or by a sub-district like Pinery Water and Wastewater, which follows a different fee structure entirely?
- Has the tiered fee schedule been finalized for this permit cycle, or is it still subject to the annual review Castle Rock Water conducts each year?
None of this changes whether Castle Rock is a place worth choosing. The town's own renewable water investment is the kind of infrastructure spending that protects long-term reliability rather than papering over a shortage. The fee structure is now sized to the house, so buyers can account for it when comparing costs.
A Few Quick Answers
Will the fee schedule change again? Castle Rock Water conducts an annual review of rates and fees, so the exact tiers and dollar amounts are subject to adjustment each year.
If you're comparing new construction against resale, or trying to figure out what a specific Castle Rock lot or floor plan actually costs once every fee is on the table, Shannon Petrone and the team at Petrone Properties can walk through the numbers with you before you write an offer. Explore more about Castle Rock or start with our buyer's guide to see how these local details fit into your broader search.
This article is general information, not legal, tax or financial advice. Consult a qualified professional about your situation.
