City and County of Denver, Colorado
Plumber Denver: The City That Chose to Dig Up the Lead
When a large American utility discovers it has tens of thousands of lead service lines, the standard answer is a chemical one. Add orthophosphate to the water, build a protective coating inside the pipe, leave the pipe in the ground. Denver Water looked at that and said no, because the phosphate would land on its own wastewater plants and on the reservoirs, streams and rivers downstream. It raised the pH instead and committed to pulling the pipes out.
That decision defines plumbing in this city more than any other single fact. This page sits under the Colorado service area in our service areas directory, and it is built on what the utility, the city and the state geological survey actually publish.
Lead Service Lines, and Why Denver Went the Hard Way
A service line is the pipe between the water main in the street and your house. In an older Denver property that pipe may be lead, and Denver Water estimates 60,000 to 64,000 homes may have one. The utility publishes an address lookup so you can check yours rather than guess, and checking is the right first move.
The treatment change came first. From March 2020 Denver Water increased the pH of the water it delivers to 8.8, up from around 7.8, to reduce the risk of lead and other metals leaching out of service lines and household plumbing. Higher pH makes the water less aggressive toward the pipe, which buys time while the physical work goes on.
The rejected alternative is the interesting part. Orthophosphate is the conventional corrosion control chemical and it works. Denver Water declined it on the grounds that it would carry through to wastewater treatment plants and on into downstream reservoirs, streams and rivers. It chose a fifteen year replacement programme instead, funded through water rates, bonds, new service fees and hydropower generation, with no direct charge to the customer.
The EPA has published a finding that the programme is effective. What that means for a homeowner is that the lead question in Denver has an official answer and an official timetable, rather than the fog that surrounds it in most cities. Details are on the utility lead reduction pages.
Four Thousand Square Miles of Collection for One City
Denver Water supplies about 1.5 million people, nearly a quarter of all Coloradans, and almost all of that water starts as mountain snowmelt. The utility makes a point that matters hydrologically: Denver is the first major user in line for that water, which is a rare position for a large city to occupy.
The collection system covers roughly 4,000 square miles, about 2.5 million acres, reaching into more than eight counties including Park, Grand, Jefferson, Summit, Teller, Douglas, Clear Creek and Gilpin. It splits into two. The South System supplies about 80 percent on average, drawing on the upper South Platte, upper Blue and Bear Creek watersheds and treating at the Foothills and Marston plants. The North System supplies the remaining 20 percent from the upper Williams Fork, upper Fraser, South Boulder Creek and Ralston watersheds.
Storage is the buffer that makes it work. Total reservoir capacity across the system is 708,250 acre feet, of which Dillon alone holds 257,304, more than a third of the whole. Some reservoirs never send water to a treatment plant at all: Williams Fork and Wolford Mountain are held for exchange and replacement obligations rather than for supply.
The plants themselves span nearly a century. The Moffat Water Treatment Plant was constructed in the 1930s and is still in operation, with the Northwater Treatment Plant added to the north side of the system. Infrastructure of that age is exactly why a utility this size thinks in fifteen year programmes rather than annual budgets.
How the Replacement Actually Runs
The Denver Lead Service Line Replacement Sequence
This is genuinely a sequence rather than a list, and the utility publishes it as one. Knowing the order tells you where you are in the process and what should happen next, which is the difference between a programme that feels arbitrary and one you can plan around.
- Check the address lookup
Denver Water publishes a map keyed to your address that tells you whether your property is one of the estimated 60,000 to 64,000 with a possible lead service line. Everything else follows from that answer, and guessing from the age of the house is not good enough.
- The utility plans a work area for the year
By the autumn of each year Denver Water identifies work areas for the following year, using an inventory built from property records, water testing and visual inspection plus a model that weights likelihood of lead, concentration of affected properties, health risk factors and the chance to coordinate with other construction.
- You receive notice, typically a month or two ahead
Once a property is identified for replacement the utility sends information about the process and the next steps. That notice usually arrives one to two months before the anticipated replacement date, which is enough time to plan access and ask questions.
- A filter arrives before the work does
Customers with a lead service line are supplied with a water pitcher and filters certified to remove lead, free of charge, until the line is replaced. Use them. Disturbing an old service line can release particles, which is precisely when filtration matters most.
- The line is replaced with copper at no direct charge
The customer-owned portion is replaced along with the utility side, at no direct cost. The programme is funded through water rates, bonds, new service fees and hydropower generation rather than by billing the affected household.
- Filtration continues for six months afterwards
The free filter supply does not stop on the day of the work. It runs for six months beyond replacement, which covers the period when residual particles from the old line can still move through household plumbing.
There is a second route that catches people by surprise in a good way. Outside the programme itself, Denver Water replaces any customer-owned lead service line it finds during a water main replacement project, again with copper and again at no direct charge. If your street is being dug up for a main, the lead question may resolve itself.
A published construction outlook covers 2026 through 2031 by neighbourhood and year, with the later years deliberately targeting the harder properties along major roads and arterials. Annual planning still refines the detail, so the outlook is a shape rather than a promise about your specific address.
The Ground You Are Digging In
Expansive Clay, and Why a Small Leak Becomes a Structural Problem
The Colorado Geological Survey is blunt about it: expansive or swelling soil is the most significant geologic hazard in this state and causes more property damage than any other natural hazard. The bentonite and montmorillonite clays underlying much of the populated Front Range can expand up to 20 percent by volume when they get wet and exert a force of up to 30,000 pounds per square foot.
For a plumber that is not a geology lesson, it is a risk model. Engineers treat a volume increase of three percent or more as potentially damaging. A slow supply leak under a basement slab, a cracked sewer lateral, a downspout discharging against a foundation, all of them do the one thing this soil cannot tolerate, which is deliver water to dry clay.
The survey lists the tells directly: cracked and heaved sidewalks, patios, driveways, and garage and basement floor slabs. If you have those and you also have an unexplained water bill, treat them as one problem rather than two. Our guide to hidden water leak signs covers how to test the meter before anybody opens concrete.
It also changes the value of drainage work. Keeping water away from the foundation is not landscaping in Denver, it is structural protection, and a plumbing repair that leaves the ground around the house wetter than it found it has solved half a problem and created another. Sewer and drain condition matters here for reasons that have nothing to do with blockages, which our sewer line repair page goes into.
Who Signs Off on the Work
Denver Permits, Quick Permits and the Gas Heater Rule
The City and County of Denver runs a quick permit route through Community Planning and Development, meaning a permit issued without plan review. On the plumbing side the single family and duplex list is generous: water heaters, water service, water softeners, backflow preventers, gas piping outlets, floor drains, showers, tubs and sinks, water closets and urinals, washers, dishwashers, garbage disposals and swimming pool piping.
Two items are explicitly outside the quick route, and both are worth knowing before you plan a job. Grease interceptors are not eligible, which matters to every restaurant and commissary kitchen in the city. Swimming pool heaters are not eligible either.
The rule that has changed most recently is a decarbonisation one. From 1 March 2023, new or replacement gas fired water heaters for commercial and multifamily structures cannot be applied for on a quick permit. That is a real scheduling difference for building owners, and it needs settling at the planning stage rather than on the day the old heater fails.
The other thing to check is jurisdiction, because the utility boundary and the permit boundary are not the same shape. Denver Water serves around 1.5 million people, far more than live inside the City and County of Denver, so being a Denver Water customer does not mean the City and County of Denver issues your permit.
Where Requests Come From
Denver Neighbourhoods and Coverage
Denver neighbourhoods differ in the ways that matter to plumbing: build era, whether the service line is likely to be lead, whether the house has a full basement, and how the ground behaves. The pre-war stock through Capitol Hill, Baker, Five Points and Park Hill is a different job from the post-2000 build in Central Park or Green Valley Ranch.
Everything listed is inside the City and County of Denver. Aurora, Lakewood, Englewood, Wheat Ridge, Arvada, Westminster, Commerce City, Edgewater, Sheridan, Littleton, Greenwood Village and Thornton are separate municipalities with their own building departments. Glendale is worth naming on its own, because it is a complete enclave surrounded by Denver, and a street address there is not a Denver permit.
Basements are the other Denver constant. Unlike the slab cities further south, most housing here has a full basement, which means the supply and drain lines are visible and reachable, and it also means a leak has somewhere to collect. That is good for diagnosis and bad for what the water does to the clay underneath.
What We Handle Here
Plumbing Services Across Denver
Service line and repipe work sits at the centre of the Denver list, and the lead programme is only part of the reason. Older Denver houses carry galvanized steel supply that closes up from the inside over decades, so falling flow at the furthest fixture is the classic tell rather than a burst. Our repiping page sets out when a system rather than a section has reached the end.
Freeze work is a genuine seasonal category here in a way it simply is not in the desert cities. Exposed hose bibs, runs through unheated garages and crawlspaces and pipework in exterior walls are where Denver plumbing actually fails in a cold snap, and the mile high pattern of bright sun and hard overnight lows means a pipe can thaw and refreeze repeatedly in a week.
Drain and sewer work is shaped by age and by clay. Older laterals in the pre-war neighbourhoods are clay pipe with root pressure on every joint, and a blockage that returns is structural rather than incidental. Camera survey first, then a decision, and where a line is scaled rather than blocked hydro jetting restores the full bore properly.
Leak detection carries an extra consequence in this city because of the soil. A leak that would be an inconvenience elsewhere is a foundation risk here, so meter isolation and pressure testing come early rather than late. Water heater work, fixture and valve replacement, gas line work and commercial plumbing through the industrial corridors round out the list.
Denver Plumbing Questions, Answered Straight
What Denver homeowners actually ask about lead service lines, expansive clay, quick permits, freeze risk and where the city snowmelt supply comes from.
Denver Water publishes an address lookup that answers exactly that, and it is the right place to start rather than guessing from the age of the house. The utility estimates 60,000 to 64,000 properties in its service area may have a lead service line, and its inventory is built from property records, water testing and visual inspection.
Two things at once. Since March 2020 it has raised the pH of the water it delivers to 8.8, up from around 7.8, which makes the water less aggressive toward lead. And it is running a fifteen year programme to physically replace lead service lines with copper at no direct charge to the customer, funded through rates, bonds, new service fees and hydropower generation.
Because of where it would end up. Orthophosphate is the conventional corrosion control additive, but Denver Water concluded it would carry through to wastewater treatment plants and on into downstream reservoirs, streams and rivers. It chose the more expensive route of pulling the pipes out instead, and the EPA has published a finding that the programme is effective.
Not directly. The utility states that replacement comes at no direct charge to the customer, including the customer-owned portion of the line. It also replaces any customer-owned lead service line it discovers during a water main replacement project, again with copper and again at no direct charge, outside the programme itself.
Yes. Denver Water supplies a water pitcher and lead-certified filters free of charge to customers with a lead service line, and the supply continues until the line is replaced and for six months afterwards. The six month tail exists because disturbing an old line can release particles that keep moving through household plumbing for a while.
Mountain snowmelt, collected across roughly 4,000 square miles reaching into more than eight counties. The South System supplies about 80 percent from the upper South Platte, upper Blue and Bear Creek watersheds. The North System supplies the rest from the upper Williams Fork, upper Fraser, South Boulder Creek and Ralston watersheds. Denver is the first major user in line for that water.
Because of the soil. The Colorado Geological Survey describes expansive clay as the state most significant geologic hazard, capable of expanding up to 20 percent by volume when wetted and exerting up to 30,000 pounds per square foot. A slow leak under a basement slab delivers exactly the water that soil cannot tolerate, and engineers treat a three percent volume increase as potentially damaging.
Water heaters appear on the city quick permit list for single family and duplex properties, meaning a permit issued without plan review. The rule is different for larger buildings: from 1 March 2023, new or replacement gas fired water heaters for commercial and multifamily structures cannot be applied for on a quick permit.
Grease interceptors and swimming pool heaters are both outside the quick permit route, along with gas fired water heaters in commercial and multifamily structures since March 2023. Everything else on the residential plumbing list, including water service, water softeners, backflow preventers and gas piping outlets, is eligible under the published conditions.
No, and this trips people up. Denver Water supplies around 1.5 million people, far more than live inside the City and County of Denver. Aurora, Lakewood, Englewood, Wheat Ridge, Arvada, Westminster, Commerce City, Edgewater, Sheridan, Littleton, Greenwood Village, Thornton and the enclave of Glendale all have their own building departments.
Lead, Clay and Cold Nights
Service lines assessed properly, leaks found before the clay under your basement finds them for you, freeze damage prevented rather than repaired, and permits taken through the right route the first time. Tell us the neighbourhood and the symptom.