Repairs, small to structural
Lids and risers. Broken or buried lids and missing risers are safety and access problems, usually the cheapest items on any inspection report and often fixed the same week.
Tees, baffles, and effluent filters. The fittings that keep solids in the tank and out of the field. When one cracks or rots away, solids migrate downstream, which is how a small part failure quietly starts a large field failure.
The building sewer. The line between the house and the tank fails in ordinary plumbing ways: root intrusion at the joints, a belly from settling soil, or a crush from vehicle traffic. Jetting or spot excavation handles most of it, and a camera run settles the diagnosis before anyone digs.
The distribution box. Settling, tilting, or root intrusion sends flow to one side of the soil treatment area and overloads it. Releveling or replacing the box restores even distribution.
Pumps and floats. Pressure-dosed systems add a pump chamber, and pumps, floats, and alarms are wear items with service lives shorter than the system around them.
The tank. A compromised tank can sometimes be sealed or relined; a collapsing one gets replaced. Tank-only replacement is its own permit category in Jefferson County, priced separately from full-system work.
The soil treatment area. The big one. A saturated, root-bound, or crushed field is not really repaired so much as rebuilt: new trenches in new soil, engineered where soils demand it. At that point the project overlaps with the installation and replacement page.
Every repair of substance runs through the county
Colorado's Regulation 43 (5 CCR 1002-43) delegates permitting for OWTS of 2,000 gallons per day or less to county public health agencies, within the statewide framework kept by the Colorado Department of Public Health and Environment. Jefferson County publishes its numbers: a permit for a new system, repair, or addition runs $1,023, a tank-only replacement $523, and a permit renewal $250, per the Jefferson County Public Health FAQ.
In Larimer and Boulder counties the same authority sits with the Larimer County Department of Health and Environment and Boulder County Public Health, whose current OWTS fees are set in the county's OWTS fee resolution (PDF). The contractor you are matched with typically handles the permit application as part of the job; the reason to know the fee structure is budgeting, not paperwork.
What repairs cost, per published Colorado sources
Small repairs, a tee, a filter, a lid, are quoted per job and sit far below the numbers that follow. For the structural end, Colorado contractors publish real figures. A Tri-Lakes-area contractor's cost guide puts full septic installation or replacement quotes commonly at $10,000 to $50,000 or more, with conventional systems at $10,000 to $20,000, pressure distribution at $15,000 to $25,000, and engineered or advanced-treatment systems above that (Tri-Lakes Contracting, contractor-published). A Denver-area company puts aerobic systems at $10,000 to $20,000 (Affordable Septic Pumping, contractor-published).
Treat all of these as published reference points, not quotes. Soils, slope, groundwater, and access decide the real number, and the independent local contractor you are matched with prices from the site itself. The pattern worth internalizing: catching a distribution box problem early is a repair; ignoring it until the field saturates is a replacement.
A repair in the middle of a sale
Boulder County. A deficient system must be fixed before the Property Transfer Certificate issues, unless the buyer signs a notarized Agreement to Repair; the county then issues a conditional certificate and the buyer has 365 days after closing to finish the work, per the county's property transfer certification instructions.
Larimer County. Needed repairs are finished first, or, when the buyer agrees to take them on, the county issues a Conditional Acceptance Document with an Agreement to Repair, per the transfer of title page. Sellers in Fort Collins and Loveland work with the same county offices either way.
Jefferson County. Use permit applications go in no less than 10 working days before closing, per the Use Permit Program page, so a deficiency found late leaves a narrow window to permit and complete a fix. Inspecting at listing time rather than under contract is the honest solution, especially in the mountain areas around Evergreen and Golden where winter access can slow the work itself.
The full program mechanics live on the transfer inspection page, and the Front Range septic transfer guide puts the whole sale timeline in one read.
Repair or replace
Some systems reach the end of the argument. Repeated field failures, a tank sized for a smaller house than the one now standing, or soils that never suited the original design all point toward replacement rather than another patch. That path, soil evaluation, county review, and new construction, is covered on the installation page. And because solids escaping the tank are what kill fields, keeping up with routine pumping is the cheapest repair-avoidance strategy there is.