Plumber Longmont: What Goes Down Your Drain Comes Back Up Your Street
Longmont does something with its sewage that almost no city on this site does. The wastewater treatment plant produces biogas in its digesters, the City cleans it, compresses it and burns it as vehicle fuel, and eleven of the twenty one trucks that collect the bins run on it. The waste leaves your house through one pipe and comes back down your street inside a fuel tank.
Before that project was built, three quarters of that gas was simply flared off. That is the City own figure, and it is the number that makes the rest of this page make sense: this is a utility that treats what arrives at the plant as a stock of materials rather than as a problem, which is unusual, and it changes what a household putting the wrong thing down a drain is actually doing.
The practical half of the page is smaller and more useful. There is a free diagnostic the City publishes that tells you in one minute whether a blockage is yours, a claims route if the City main damaged your property, a licensing rule that treats plumbing differently from electrical, and a graywater ordinance dated November 2025. Everything was read on 1 August 2026, with sources named at the foot.
Why a plumber longmont households call is working on a fuel supply
The City began construction at the wastewater treatment plant in 2018 and completed the project in late 2019, working with CGRS, a Fort Collins environmental services and construction company. It converts biogas generated through anaerobic digestion into renewable natural gas, and that gas powers part of the City fleet of trash collection trucks.
The engineering is published in four steps. Anaerobic digestion breaks down organic material and produces biogas, roughly 60 per cent of which is methane. A treatment skid strips out the contaminants that prevented it being used in engines directly: hydrogen sulphide, siloxanes and moisture. Compressors then take it from about 100 psi to over 4,000 psi. New trucks with compressed natural gas engines fill from a fuelling station on the site.
The City calls itself the first city along the Front Range to implement a renewable vehicle fuel project, and says other utilities have been looking at it as a model. That is its own claim about itself and we are reporting it as such rather than confirming it.
One other city on this site digests its sewage gas, and it does the opposite thing with it
Our Sunnyvale page describes a treatment plant that runs largely on biogas produced in its own digesters and in an adjacent landfill, satisfying the majority of its own operational energy demand. The gas never leaves the building. It is a plant that feeds itself.
Longmont sends its gas out. The plant keeps only what it needs for heat, and the surplus that used to be burned off into the air now goes through a skid, a compressor and a fuelling station into a vehicle that drives away. Same biology, same digester, and a completely different destination.
Why that matters to a household rather than to an engineer: it is the clearest possible statement of what a wastewater plant actually is. Not a place where a problem is disposed of, but a place where a mixed material is separated into parts that each go somewhere specific. Everything you send down a drain is being sorted at the other end by somebody who has plans for it.
What arrives at the Longmont plant as one substance and leaves it as four
The City publishes its treatment sequence as six stages: preliminary, primary, secondary, tertiary, disinfection and solids treatment. Read it as a sorting operation rather than a cleaning operation and the four exits become obvious. Each one leaves under different rules and goes to a different place.
Water, to the creek
Treated effluent is discharged to St. Vrain Creek at an average daily flow of about 8.0 million gallons a day. Before it goes, a nitrifying trickling filter removes ammonia, because ammonia is toxic to aquatic life, and ultraviolet light handles disinfection.
Gas, to a fuel tank
Methane from the digesters, cleaned and compressed, into the trucks. The only one of the four exits that leaves the site under its own power and comes back down your street.
Trash and grit, to a dumpster
Preliminary treatment screens out trash, which is washed, compacted and sent to landfill. Grit settles out, is pumped from the bottom of a basin and washed to remove organics before it joins the same dumpster. This is where flushed wipes end up.
Solids, to handling
Settled solids from the clarifiers are thickened to reduce volume and sent for stabilisation and disposal, and most of the solids from the secondary clarifiers are returned to the aeration basin to keep the biological process running.
Sixty seconds, no charge, no equipment
The sentence on the City sewer page that is worth more than a call out
The City publishes a test that costs nothing and answers the only question that matters first. If sewage backs up into your basement or crawl space only when you run water in your own home or business, it says, the problem is most likely in your service line system, and you may need to call a plumber.
That is a clean logical separation. Your own water going in is the only thing changing, so the restriction is downstream of you and upstream of the main. If it backs up when nothing in the building is running, the source is somewhere you do not control.
The ownership line behind it is the standard one, stated plainly. The sewer service line is owned and maintained by the property owner, and it is defined as the length of pipe between the building and the sewer main, which is usually in the street, easement or alley. Property owners are responsible for clean up and repair of anything originating in that line, including repairing damage to the street or driveway if necessary. Our sewer line repair page covers the decision that follows.
It will investigate, it will clean the main, and it publishes where a claim goes
The City states it will send a crew to investigate a reported problem and clean the main sewer line if it is plugged. Water Utilities takes those calls Monday to Friday, 8am to 5pm. Outside those hours the route is Longmont Police Dispatch, who notify a utility technician to respond.
Then a detail most cities leave you to discover the hard way. If a problem is found in the City main that caused damage to your property through your service line, the City states a claim should be sent through its Risk Management Office on 303-651-8435. That is a published route to a specific office rather than a general complaint address, and it is worth knowing before an insurer asks who you notified and when.
The City names the three usual causes of plugged sewer lines and none is exotic: tree roots, grease accumulation, and structural problems. That is also the order in which they are worth ruling out. Drain cleaning covers the first pass, hydro jetting the grease-laden case, and emergency plumbing the middle of the night version.
The City will give you a Fat Trapper, and the reason is upstream of the plant
Public Works and Natural Resources offers free Fat Trappers to Longmont residents, along with free replacement bags. The container is a white plastic tub with a lid that sits in a fridge, a cupboard or on a worktop, holding a heat resistant bag that collects fry grease. When the bag is about three quarters full you seal it and put it in the bin, and you keep the tub and refill it.
They are available from the Service Center at 1100 South Sherman Street on 303-651-8416 and from the Civic Center. Cooled cooking oil in a sealed container can also be taken to the Longmont Recycling Center on Martin Street, where the City says collected oil is recycled by local businesses for biodiesel.
The City reason for all this is a plumbing reason rather than an environmental slogan. Fry grease poured down a drain or a toilet coats the sewers, and the City names the consequences in order: slow drains, blockages, sewer back ups, and exposure to the pathogens in raw sewage. Grease is also the second of the three causes of plugged lines it names elsewhere.
Two watersheds and a tunnel under a mountain range
Longmont drinking water is entirely surface water
There is no groundwater in the published supply. The City states its drinking water is all surface water from streams, lakes and reservoirs fed by snowmelt and rainfall in the St. Vrain Creek watershed and in the Colorado and Fraser Rivers on the west slope.
The local half is two forks. The North St. Vrain watershed stores water in Ralph Price Reservoir, the South St. Vrain stores it in Burch Lake, and the two forks combine to form the St. Vrain Creek near Lyons. From there the Highland and Palmerton Ditches carry it to the treatment centres.
The other half crosses the continental divide. Water from Grand County reaches Longmont via the Colorado-Big Thompson project, operated by the Northern Colorado Water Conservancy District, flowing through the Adams Tunnel and arriving through Carter Lake, the St. Vrain Supply Canal and the Southern Water Supply Pipeline.
A naming note worth making. The Big Thompson in that project name is not the Big Thompson River, which leaves the mountains at Loveland about fifteen miles north. One is a river and the other is a diversion scheme, and they are easy to conflate.
A single town pump, a bucket brigade, and a burned high street
The City publishes its own origin story and it is unusually specific. Settlers along the St. Vrain used stream water directly. As the colony grew, individuals went into business hauling water from the streams for customers to store in barrels and cisterns. There was one town pump, at the corner of 4th and Main.
On 8 September 1879 the 300 block of Main Street caught fire and was completely destroyed. The only water available to fight it came from that town pump and from a bucket brigade formed down to St. Vrain Creek. The first fire fighting company was formed the following year, and on 1 April 1882 Longmont taxpayers voted a 70,000 dollar bond to build the first pressurised waterworks system.
That is worth two minutes on a plumbing page for one reason. Pressure in this town was bought deliberately, by vote, after a demonstration of what its absence costs. Most residential plumbing arguments are about pressure in the end, and it is a useful reminder that the mains are a public work with a purpose rather than a background condition.
One question worth asking before anybody starts
Plumbing here is a double registration and electrical is not
The City requires contractors to obtain the appropriate licence before performing construction or trade work, and publishes the classes. General contractors hold a Class A, B or C licence, and all three expressly exclude electrical, plumbing, mechanical, fire extinguishing and elevator work unless the holder is separately licensed under a specialty trade.
Then the two trades diverge. For electrical, the City states that no person shall receive a permit without an electrical contractor licence from the State of Colorado. For plumbing, it states that in order to contract for the installation, altering or repairing of plumbing fixtures and apparatus of any kind, a person must register with the State of Colorado as well as with the Division of Building Inspection.
And the City registration is not just a name on a list. It has to include the applicant name, the place of business, and the Master Plumber name and licence number. That last item is the practical one, because it is a specific thing you can ask a contractor for and check.
Reading those two paragraphs as an asymmetry is our observation rather than a City statement. What the City publishes is the two requirements; that plumbing carries a second, local step which electrical does not is simply what the page says when you set the two side by side.
Graywater, and the drought level as it stood in August 2026
Graywater first, and deliberately briefly. Longmont does not currently permit the installation of graywater systems. In November 2025 City Council passed Ordinance O-2025-73 prohibiting their installation, and the City states the decision does not close the door on future adoption.
We are not going to explain the Colorado graywater framework on this page, because our Boulder page already sets out the state regulation, the legislation behind it and the reasoning a Front Range city gives for declining, and Boulder is ten miles away in the same county under the same law. Two pages restating one statute would read as one page. What belongs here is the ordinance number and the date, and those are above.
The City also publishes twelve formal Guiding Water Principles that inform how the utility is operated, a 2025 Water Efficiency Plan, and a set of supply projects including the Nelson Flanders treatment plant expansion, the Price Park tank replacement, the Windy Gap Firming Project at Chimney Hollow Reservoir, and a Union Reservoir enlargement from 12,000 acre feet to 32,000. We quote none of those documents beyond naming them.
Where a plumber longmont residents call actually works
Longmont sits at the foot of the Front Range where the St. Vrain leaves the hills, and the housing stock runs from nineteenth century brick near Main Street out to subdivisions built in the last fifteen years. The practical consequence is that build era predicts the pipe here more reliably than the postcode does, and the two ends of that range want completely different first questions.
Old TownMain Street corridorProspectSouthmoor ParkLanyon ParkUte CreekClover BasinUnion Reservoir edge
Longmont is one of four Front Range cities on this site. Boulder is the county seat ten miles south west, Loveland is fifteen miles north, and Denver and Littleton sit down the corridor with entirely separate utilities and rules. Nothing on this page transfers to any of them, and that is the point of writing them separately.
We state no coverage promise, no response time and no crew or office of our own for any of the areas named above. They are listed because ground, build era and utility arrangements differ across the city, not as a service claim.
Longmont Plumbing Questions, Answered Straight
A free self test, a published claims office, a double registration, and bin lorries running on what you flushed.
The City publishes a free test. If sewage backs up into your basement or crawl space only when you run water in your own home or business, the problem is most likely in your service line system and you may need to call a plumber. If it happens when nothing in the building is running, report it: the City will send a crew to investigate and will clean the main sewer line if it is plugged. Water Utilities takes calls Monday to Friday 8am to 5pm, and after hours the route is Longmont Police Dispatch, who notify a utility technician.
You do. The City defines the sewer service line as the length of pipe between the building and the sewer main, which is usually in the street, easement or alley, and states it is owned and maintained by the property owner. Property owners are responsible for clean up and repair of problems originating in that line, including repairing damage to the street or driveway if necessary. That last clause is the one that surprises people, because street restoration is a real cost line rather than a formality.
The City publishes a route for exactly that. If a problem is found in its main line that caused damage to your property through your service line, it states a claim should be sent through the City Risk Management Office on 303-651-8435. We make no claim about what any particular claim will produce, and we quote no timescale, because the City publishes none on the page we read.
On gas made from it, yes. The City converts biogas generated by anaerobic digestion at the wastewater treatment plant into renewable natural gas, and states that eleven of its twenty one diesel collection trucks have been replaced with trucks capable of running on it. Construction began in 2018 and the project completed in late 2019. Before it was built, the City says 75 per cent of the biogas was flared.
Because grease is one of the three causes of plugged sewer lines it names, alongside tree roots and structural problems. Public Works and Natural Resources offers free Fat Trappers and replacement bags to residents from the Service Center at 1100 South Sherman Street on 303-651-8416 and from the Civic Center. Cooled cooking oil in a sealed container can also go to the Longmont Recycling Center on Martin Street, where the City says it is recycled by local businesses for biodiesel.
No. In November 2025 City Council passed Ordinance O-2025-73 prohibiting the installation of graywater systems, and the City states it does not currently permit them while adding that the decision does not close the door on future adoption. We deliberately do not restate the Colorado framework here because our Boulder page, ten miles away in the same county under the same law, already covers it in full.
The City page says a registration with both. For plumbing, a person must register with the State of Colorado as well as with the City Division of Building Inspection, and that City registration must include the applicant name, the place of business, and the Master Plumber name and licence number. For electrical, the page describes a State of Colorado contractor licence and no second city step. Asking for the Master Plumber name and number is a fair and easy check.
All of it is surface water. The St. Vrain Creek watershed supplies the local half, with the North fork stored in Ralph Price Reservoir and the South fork in Burch Lake, the two joining near Lyons and running on through the Highland and Palmerton Ditches. The rest crosses the continental divide from the Colorado and Fraser Rivers via the Colorado-Big Thompson project, the Adams Tunnel, Carter Lake, the St. Vrain Supply Canal and the Southern Water Supply Pipeline.
As read on 1 August 2026 the City published a water shortage response level of Mild, under a 2026/2027 Water Supply and Water Shortage Implementation Plan. At that level the City reduces consumption by 10 per cent at its own greenways, parks, golf courses and facilities, and residents are encouraged rather than required to do the same. A response level changes, so check the current one rather than relying on this.
Because eight other city pages on this site already describe municipal sewer smoke testing, and Longmont publishes nothing about it those pages do not already cover. The City does run it, and if a notice arrives the short version is that the smoke is a survey and not a fault. We would rather point you at that than write a ninth version of the same explanation.
The short version for a plumber longmont job
Run the City own test first. If it only backs up when you run water, it is almost certainly your service line and the street restoration is yours too, so price that into the job rather than discovering it. If it backs up with nothing running, report it before you pay anybody, because the City investigates and clears its own main.
Ask any contractor for the Master Plumber name and licence number on their City registration, because Longmont requires that entry in addition to the state one. Keep the fat out of the drain, take the free tub if you want one, and check the current drought response level before planning irrigation work.
Sources, disagreements, and what we refused to state
Everything below was read on 1 August 2026. Programmes, ordinances, contact routes and drought levels change, so confirm current requirements with the City of Longmont before relying on anything above.
The 2018 construction start and late 2019 completion, the CGRS partnership, the anaerobic digestion description, the 60 per cent methane figure, the statement that 75 per cent of biogas was previously flared, the hydrogen sulphide, siloxane and moisture contaminants, the treatment skid, the 100 psi to over 4,000 psi compression, the eleven of twenty one trucks, the 50 to 70 per cent expected biogas use and the first on the Front Range claim come from the City biogas and renewable natural gas page.
The 17 million gallon per day rating, the approximately 8.0 million gallon average daily discharge to St. Vrain Creek, the six treatment stages, the screening and grit handling, the primary clarification and thickening, the activated sludge process, the nitrifying trickling filter for ammonia and the ultraviolet disinfection come from the City wastewater treatment page. The observation that the plant runs at under half its rated capacity on an average day is our arithmetic on those two published figures and is not a City statement.
The service line ownership definition, the run water self test, the tree roots, grease and structural problems causes, the street and driveway restoration responsibility, the Monday to Friday 8am to 5pm hours, the Longmont Police Dispatch after hours route, the crew investigation and main cleaning statement, the Risk Management Office claims route on 303-651-8435 and the annual trenchless sewer rehabilitation programme come from the City sewer lines page.
The free Fat Trappers and replacement bags, the container description and its use, the Service Center address at 1100 South Sherman Street and 303-651-8416, the Civic Center availability, the Longmont Recycling Center on Martin Street, the biodiesel recycling statement and the slow drains, blockages, back ups and pathogen consequences come from the City Fat Trappers page.
The all surface water statement, the St. Vrain watershed, Ralph Price Reservoir, Burch Lake, the confluence near Lyons, the Highland and Palmerton Ditches, the Colorado-Big Thompson project, the Northern Colorado Water Conservancy District, the Adams Tunnel, Carter Lake, the St. Vrain Supply Canal, the Southern Water Supply Pipeline, the 1838 trading fort, the town pump at 4th and Main, the 8 September 1879 fire, the bucket brigade, the 1880 fire company, the 1 April 1882 bond of 70,000 dollars, the Mild drought response level and its 10 per cent City facilities reduction, the twelve Guiding Water Principles and the named supply projects come from the City water resources and supply page.
The graywater position, Ordinance O-2025-73 of November 2025 and the statement that the decision does not close the door come from the City graywater page. The contractor licence classes, the specialty trade exclusions, the electrical state licence requirement and the plumbing double registration including the Master Plumber name and licence number come from the City contractor licence types page.
The source disagreement, printed rather than resolved. The biogas page states that the Waste Services division uses over 100,000 gallons of diesel fuel per year, and then bases its own savings illustration on no longer using 90,000 gallons per year. Both figures are on the same page. We adopt neither and we quote no saving figure.
Two figures refused for being unusable rather than unavailable. The published annual benefit from renewable fuel credits is printed with a missing digit in its upper bound, so we do not repeat it. And the page states that the remaining diesel trucks were expected to be replaced in 2024, which is now in the past, so we state the eleven of twenty one figure as published and make no claim at all about the current composition of the fleet.
Two subjects refused because other pages on this site already own them. Municipal sewer smoke testing, which Longmont runs and publishes a page about, is covered on eight other city pages here and nothing in the Longmont version adds to them. And the Colorado graywater framework is set out on our Boulder page, in the same county under the same law, so this page keeps only the ordinance number and the date.
The hydro question, answered honestly. We looked specifically for a municipal hydroelectric story here and did not find one on the City water pages. No claim is made about Longmont generating power from its own water supply. Two other pages on this site do carry that subject, in two different senses, and neither was imported here.
Every water, sewer, stormwater and development fee, every rate from the 2025 to 2027 schedule, and every permit and inspection fee, because no fee or rate document was opened. Every water quality result, hardness figure, lead inventory finding and PFAS figure, because those live in reports we did not open. No capacity, cost or completion date for the Nelson Flanders expansion, the Price Park tank, the Windy Gap Firming Project or any other named supply project.
No mileage of water or sewer main, no manhole or service connection count, no population figure, and no statement about which Longmont streets carry which pipe material or which are scheduled for rehabilitation. No plumbing code edition, because we did not open the building codes page. No response time, crew count, coverage promise or price, and no office, address or crew of ours is stated for Longmont.
Nearby and related pages written to the same standard: our Colorado hub for statewide coverage and routing, Boulder for the graywater framework and backflow tracking, Loveland for the Big Thompson River and industrial pretreatment, Denver and Littleton for the metro corridor, and Sunnyvale for the other way a treatment plant uses its own gas.