Boulder, Boulder County, Colorado
What a Plumber Boulder CO Homeowners Hire Has to Check Twice
Two of the questions Boulder households ask most often about their plumbing have answers here that are more complicated than yes or no. Does my house need a backflow prevention assembly, and can I reuse the water from my shower and washing machine. The city answers both in writing, and in both cases the answer contains a distinction that is easy to miss and expensive to get wrong.
On backflow, the city states that a device can be required by building, fire or plumbing code and still not be tracked by its own Backflow Prevention Program. On graywater, it states that it does not currently permit reuse systems, having opted out under state law in January 2026, and that it can opt back in later. Neither is an absence of rules. Both are rules with a gap where the reminder would normally be.
The Sentence Worth Reading Twice
Required and Untracked Are Not the Same Thing
The city puts it plainly on its Backflow Prevention service page. The programme requirements are not meant to contradict building, fire or plumbing codes, which may require a residence to have a backflow prevention assembly like those required on residential sprinkler systems. When backflow prevention assemblies are otherwise required, they must be installed, but will not be tracked by the Backflow Prevention Program.
It repeats the point on the small multi-unit page, from the other direction: backflow assemblies may be required by plumbing code, even though the backflow program does not track them per state regulations. Two pages, two departments worth of wording, one idea. The list the city keeps and the list of devices that must exist are not the same list.
The practical consequence is ours to draw and we will label it as ours. If an assembly is not tracked, no annual notice arrives, no portal entry falls due and nothing at all prompts anybody to test it. A device fitted in 2011 to satisfy a sprinkler requirement can sit untested for fifteen years without a single letter, and the first anybody hears about it is when it fails. That is not a criticism of the programme, which is scoped by state regulation. It is simply a maintenance job that has no external alarm attached.
Who Is In and Who Is Out
The Boulder Exemption Ladder, Counted in Dwelling Units
The city says approved backflow assemblies are required on all commercial, industrial, irrigation, fire and multi-unit residential water lines, with requirements detailed in state drinking water regulations, the Boulder Revised Code and Boulder Design and Construction Standards. Underneath that headline sits a ladder, and the rung you are on is decided by how many dwelling units share your meter connection.
Multi-unit, in the city definition, means two or more separate dwelling units served by one meter connection. Nine or more dwelling units must comply with installation and annual testing requirements, and the city says larger multifamily properties represent an increased risk for backflow and cross connections and will not be exempt. Three to eight dwelling units may qualify for an exemption. Duplexes are typically not tracked.
- There is an auxiliary water source on the property
- There is a dedicated irrigation line tapped off the main
- There is a fire system tapped off the main
- There is another hazard as identified by the Backflow Prevention Program
Read that as a list of triggers rather than a list of duties. A single family home in Boulder is generally outside annual testing, and then somebody adds an irrigation tap or a residential sprinkler system, and the property quietly changes category. The change happens at installation, not at renewal, which is why it is worth raising during the quote for the irrigation work rather than afterwards.
Applying, and Being Refused
How the Small Multi-Unit Exemption Actually Works
An exemption here is granted rather than claimed, and the city is careful about the difference.
- Check that the property qualifies at all
A small multi-unit property has eight or fewer dwelling units. Nine or more is outside the scheme entirely and no application will change that.
- Meet every criterion, not most of them
Properties must meet all of the criteria listed on the Small Multi-Unit Exemption Application. The city asks that you review the application and the FAQ carefully before submitting.
- Submit, and understand that submitting is not qualifying
The city states directly that submitting the application does not ensure exemption, and that you must receive written approval from Backflow Prevention Program staff.
- Expect a possible survey
The city says it may need to conduct an on site cross connection survey to assess whether an exemption can be granted, which is an inspection of the actual plumbing rather than a paperwork review.
- Treat the result as reviewable
Exemptions are not permanent. Any and all are subject to review and may be retracted in light of property modifications that introduce cross connections, or regulatory changes at state, city or programme level.
There is one further clause with teeth. If an imminent risk to the city drinking water is discovered that was not disclosed, or was misrepresented on the exemption form, the immediate installation and testing of an approved assembly will be required. Generally, the city says, changes that force compliance on previously exempt properties will be handled by notifying the responsible party and developing a compliance schedule. The word immediate is reserved for the case where the form was wrong.
Two Lines, Two Answers
The Dedicated Line Carve Out, and What Failing Costs
One of the more useful clauses on the city page covers the property that meets every exemption criterion except that it has a dedicated lawn irrigation or fire line. The answer is not all or nothing. The domestic service line remains exempt from installation and annual testing, and the specific dedicated line in question must still comply with backflow prevention requirements.
The city gives its own worked example: if a currently exempt single family residence acquires a dedicated irrigation water line, that irrigation line will need an approved backflow prevention assembly installed and tested annually per state and city requirements. The house does not change status. The new pipe does. Mixed use is treated differently again, and the city is unambiguous: in all circumstances, a commercial property must follow backflow regulations.
| What happens on noncompliance | Fee | Code section |
|---|---|---|
| Water shut-off warning hangtag | $59 | BRC 4-20-23 (g)(5) |
| Water shut-off | $113 | BRC 4-20-24 |
| Additional penalties | $250 to $1,500 | BRC 11-1-25 (g) |
All annual test reports for backflow assemblies must be submitted online by a certified tester through the city Backflow Web Portal, where a tester registers, submits a test and adds a new assembly. The programme can be reached at nobackflow@bouldercolorado.gov or on 303-413-7401, at 5605 North 63rd Street.
The Distinction People Get Wrong
A Water Heater Is Not a Hydronic Heating System
The city defines the terms because the terms decide the requirement. A hydronic heating system circulates heated water, often mixed with chemical additives like antifreeze, throughout a property in order to heat the home when it is cold, and boilers and heat exchangers are common hydronic heat sources. Water heaters are not considered hydronic heating systems, because they simply heat water for domestic use.
The concern with a boiler is chemical. The city says the largest concern is that boilers sometimes use chemicals like antifreeze to keep lines from freezing, and that chemical solutions may be run through boilers for cleaning. In either case those chemicals could get back into the drinking water supply during a backflow event, so installation and annual testing of an RPZ backflow prevention assembly may be required.
And then the trap, which is the single most useful sentence for anybody who already has protection fitted. Sometimes boilers are isolated and protected with a non testable backflow prevention device, which does not meet state regulations for a testable backflow prevention assembly installed as containment. If the boiler is determined to be the only high hazard cross connection on the water line, installation and annual testing of an RPZ assembly may be required to isolate it. Having a device is not the same as having the right device.
Definitions That Change an Assessment
Process Water, Make Up Water and How Boulder Counts Storeys
Two more definitions on the same page are worth carrying, because they are what an assessment turns on. Process water becomes contaminated during an industrial process, such as photo processing or X ray development. Make up water can become contaminated when it is mixed with chemicals like antifreeze for the purpose of supplying boilers, cooling towers, solar water heating systems or other sources of cooling and heating. Typical sources named include photo labs, darkrooms, X ray machines, hydronic heating systems and solar water heating systems.
The storey count is more prosaic and more likely to come up. The city assumes three storey buildings to be about 36 feet in height, at 12 feet per storey above ground. Because plumbing generally enters at the top of the basement, basements need not be considered in the overall calculation of stories, and attic space with no plumbing should be disregarded in any calculations.
A Formal No, With a Date
Graywater Reuse in Boulder, and Why the Answer Is Currently No
Graywater is a term for wastewater from bathtubs, showers, bathroom sinks, laundry room sinks and most water from clothes washers, and the city is explicit that it does not include wastewater from kitchen sinks, dishwashers or toilets. Graywater reuse means taking that water before it goes to the sewer, treating it, and using it to flush toilets or sending it to below ground irrigation systems to water outdoor plants and trees.
The city also states the limits of the treated result: it is clean enough for those two uses after a small amount of treatment, but it is not safe for drinking, playing, cleaning, use in sprinkler systems or irrigation of some food crops. That list is worth keeping even in a city that does not permit the systems, because it is the correct answer to the most common misunderstanding about what graywater is for.
| When | What changed |
|---|---|
| 2015 | Colorado adopts Regulation 86, allowing cities to permit graywater reuse systems only if the city creates a local graywater control program |
| Under Regulation 86 | That program must oversee all regulatory activities including design review, inspection, enforcement, tracking and addressing complaints |
| House Bill 24-1362 | Requires cities to decide by January 2026 whether they will opt out of creating a local graywater control program |
| January 2026 | The City of Boulder made municipal code changes to comply with state law and initially opted out of graywater reuse |
| Later, if the city chooses | Cities can opt in at a later time after initially opting out, and the city states the code change does not prevent it |
The reason the city gives is resourcing rather than hostility. It says it is a strong supporter of water conservation, that setting up a local control program would require time and resources currently dedicated to other conservation programmes that yield greater water savings at lower cost, and that it will continue to weigh the costs and benefits. It names the things that would change its mind: improvements in graywater technology that reduce maintenance and cost, resource availability, Boulder unique water rights, community interest and conservation potential. Feedback goes to bouldersaveswater@bouldercolorado.gov.
Around the City
Where This Applies Across Boulder
The neighbourhoods below are geography rather than a coverage promise, and this page states no response time because we do not publish those anywhere on this site. What varies across them here is the mix of single family, duplex and small multi-unit property, which is precisely the variable the backflow ladder above turns on, and how many properties carry dedicated irrigation lines.
Our wider Colorado position sits on the state page, which already describes the Boulder foothills band and notes that Boulder County runs its own code adoption calendar separate from Denver and Colorado Springs. The other Colorado city pages we have published are Denver, Colorado Springs, Fort Collins, Arvada and Littleton, and every one of them has its own utility rules.
Boulder Plumbing Questions, Answered Straight
A backflow device that can be required and untracked at once, an exemption ladder counted in dwelling units, a boiler rule that turns on one definition, and a graywater decision dated January 2026.
Usually not for annual testing purposes, and there are four exceptions. The city says residential single-unit customers do not have to comply with Backflow Prevention Program requirements unless there is an auxiliary water source on the property, a dedicated irrigation line or fire system tapped off the main, or another hazard identified by the programme. Separately, building, fire or plumbing codes may require an assembly regardless, and those requirements are not waived by the programme scope.
It means two different systems are in play. The city states that its programme requirements are not meant to contradict building, fire or plumbing codes, which may require a residence to have an assembly like those on residential sprinkler systems, and that when assemblies are otherwise required they must be installed but will not be tracked by the programme. Our conclusion, not the city, is that an untracked device generates no annual notice, so nothing external will ever prompt a test of it.
By the meter, not the building. The city states that multi-unit properties include two or more separate dwelling units served by one meter connection. From there the ladder is by count: nine or more dwelling units must comply with installation and annual testing, three to eight may qualify for an exemption, and duplexes are typically not tracked by the programme at all.
It can qualify, which is not the same as being exempt automatically. Properties with three to eight dwelling units may qualify for an exemption from the city installation and testing requirements, but must meet all of the criteria listed on the Small Multi-Unit Exemption Application. The city states that submitting the application does not ensure exemption and that you must receive written approval from Backflow Prevention Program staff. It may also conduct an on site cross connection survey.
No. The city says exemptions are not permanent, that any and all are subject to review, and that they may be retracted in light of property modifications that introduce cross connections or regulatory changes at state, city or programme level. It adds that if an imminent risk to the city drinking water is discovered that was not disclosed or was misrepresented on the exemption form, immediate installation and testing of an approved assembly will be required.
The line changes category, not the house. The city says that where a property meets the exemption criteria in all areas except the presence of a dedicated lawn irrigation or fire line, the domestic service line remains exempt from installation and annual testing, and the specific dedicated line must still comply. Its own example is a currently exempt single family residence acquiring a dedicated irrigation water line, which then needs an approved assembly installed and tested annually.
The city recommends testing it anyway. It says backflow prevention assemblies protect both the city water supply and the drinking water within the property itself, so if an assembly is installed at a property granted an exemption it strongly recommends annual testing, while noting the programme will not need to track the assembly or its tests. That is a case where the reminder is entirely yours to set.
The city publishes the ladder with code citations. Failure to comply may result in a water shut-off warning hangtag carrying a $59 fee under BRC 4-20-23 (g)(5), a water shut-off carrying a $113 fee under BRC 4-20-24, and additional penalties ranging from $250 to $1,500 under BRC 11-1-25 (g). All annual test reports must be submitted online by a certified tester through the city backflow web portal.
If it circulates heated water to heat the property, yes. The city defines hydronic heating as circulating heated water, often mixed with chemical additives like antifreeze, throughout a property to heat the home, and names boilers and heat exchangers as common sources. It also states clearly that water heaters are not considered hydronic heating systems because they simply heat water for domestic use, which is the distinction most people get wrong.
Not necessarily. The city says boilers are sometimes isolated and protected with a non testable backflow prevention device, which does not meet state regulations for a testable assembly installed as containment. If the boiler is determined to be the only high hazard cross connection on the water line, installation and annual testing of an RPZ assembly may be required to isolate it. Having a device fitted is not the same as having a compliant one.
By plumbed floors above ground. The city assumes three storey buildings to be about 36 feet in height, at 12 feet per storey above ground. Because plumbing generally enters at the top of the basement, basements need not be considered in the overall calculation of stories, and attic space with no plumbing should be disregarded in any calculations. That can move a building a whole category in an assessment.
Not at present. The city states that it does not currently permit graywater reuse systems. Colorado adopted Regulation 86 in 2015 allowing cities to permit them only if the city creates a local graywater control program, and House Bill 24-1362 required cities to decide by January 2026 whether to opt out of creating one. Boulder made municipal code changes to comply with state law and initially opted out in January 2026.
No. The city says cities can opt in at a later time after initially opting out, and that this initial code change does not prevent the city from allowing graywater reuse in the future. It lists what it will weigh: improvements in graywater technology to reduce maintenance challenges and decrease costs, availability of resources to maintain a programme, Boulder unique water rights, community interest and the potential for water conservation. Feedback goes to its water conservation address.
The city definition is specific. Graywater is wastewater from bathtubs, showers, bathroom sinks, laundry room sinks and most water from clothes washers, and it does not include wastewater from kitchen sinks, dishwashers or toilets. Reuse means treating that water and using it to flush toilets or sending it to below ground irrigation systems. It is not safe for drinking, playing, cleaning, use in sprinkler systems or irrigation of some food crops.
The city gives resourcing as the reason rather than principle. It says permitting graywater would require development of a local graywater control program with related rules, processes and staff to make sure systems are installed properly, comply with state regulations and keep community members safe, and that Boulder does not currently have such a program in place. It states that setting one up would take time and resources currently dedicated to conservation programmes that yield greater savings at lower cost.
Ask Before the Work, Not After
Plumber Boulder CO Work That Turns on Two Definitions
Most of the risk on this page is triggered by adding something rather than by owning something. A dedicated irrigation line, a residential sprinkler system, a boiler with antifreeze in it, a ninth dwelling unit. Each of those moves a Boulder property from one category to another, and the city will not necessarily write to you about it. Raise the backflow question during the quote for whatever you are adding, and the answer costs nothing.
Related work on this site: repiping and fixture repair cover the work most often triggering the questions above, and our Denver plumbing page and Fort Collins plumbing page cover two Front Range neighbours with their own rules. The state picture sits on our Colorado plumbing page.
Sources for the requirement that approved backflow assemblies be fitted on all commercial, industrial, irrigation, fire and multi-unit residential water lines, the general exemption of single-unit homes and duplexes from annual testing per state regulations, the four triggers that end a single-unit exemption, the statement that programme requirements are not meant to contradict building, fire or plumbing codes and that otherwise required assemblies must be installed but will not be tracked, and the definition of multi-unit as two or more dwellings on one meter connection: the City of Boulder Backflow Prevention service page.
The same page is the source for the nine-unit threshold, the online portal requirement for certified testers, and the noncompliance fees of $59, $113 and $250 to $1,500 with their Boulder Revised Code citations: the City of Boulder Backflow Prevention service page.
Sources for the eight-or-fewer definition of a small multi-unit property, the three to eight exemption band, the statement that duplexes are typically not tracked, the requirement to meet all criteria on the Small Multi-Unit Exemption Application, the statement that submitting does not ensure exemption and that written approval is required, the possible on site cross connection survey, and the impermanence and retraction of exemptions: the city Backflow Prevention Small Multi-Unit Property FAQ.
That FAQ is likewise the source for the immediate installation requirement where an imminent risk was undisclosed or misrepresented, the dedicated irrigation and fire line carve out with its worked example, the rule that a commercial property must follow backflow regulations in all circumstances, the hydronic heating and water heater definitions, the antifreeze and cleaning chemical concern, the RPZ requirement, the non testable device warning, the process and make up water definitions, and the storey counting method.
Sources for the graywater definition and its exclusions, the meaning of graywater reuse, the unsafe uses list, the statement that the city does not currently permit graywater reuse systems, Colorado Regulation 86 of 2015 and the local control program requirement covering design review, inspection, enforcement, tracking and complaints, House Bill 24-1362 and the January 2026 opt out decision point, the municipal code changes made to comply and the initial opt out in January 2026, the statement that cities can opt in later, the resourcing reason given, the list of considerations for a future decision and the feedback address: the city Graywater in the City of Boulder project page.
The observation that an untracked assembly generates no annual notice, and that nothing external will therefore prompt a test of it, is OURS and is labelled as ours in the body text above. The explanation of why building height bears on backpressure is likewise general engineering context supplied by us and is not a city statement.
No water, wastewater or stormwater rate is quoted anywhere on this page, because the monthly water user charges and plant investment fee pages were not opened. No water budget allocation figure is stated. No hardness or other water quality figure is stated, because the drinking water quality data page was not opened. No count of tracked backflow assemblies or granted exemptions is stated. No price for an RPZ assembly or an annual test is stated, because the city publishes none. No system mileage and no 2013 flood damage figure is stated.
No response time, crew count, office or address of ours is stated for Boulder, and no coverage claim is made beyond what our Colorado page already sets out. Codes, fees, exemption criteria and the graywater position are all reviewable and the city says so, so confirm current requirements with the City of Boulder Backflow Prevention Program or Water Conservation before relying on anything above.