Renting Out an Older Denver Home: Sewer Lines, Radon, Lead, Wiring and Swamp Coolers

Denver's housing is older than you think

Denver's housing stock is a mix of Victorian-era homes, 1920s bungalows, post-war ranches and modern builds. According to 2024 Census data for Denver County, the median home was built in 1979, about half of all housing units were built before 1980, and about 16% were built before 1940.

Older homes have character renters love: hardwood floors, front porches and walkable neighborhoods like Washington Park, Highland, Park Hill and Baker. They also have systems that are decades old. Here's what to check before, and while, you rent one out.

Sewer lines: the expensive surprise

Many older Denver homes have clay or cast-iron sewer lines that tree roots, shifting soil and age can crack or block.

Who's responsible? The City of Denver says it is only responsible for the main public sewers. If a backup is in your private line, it's your job to call a plumber. Contractors generally describe the owner's responsibility as running from the house to the connection at the main, often including the part under the street.

What to do:

• Get a camera scope before buying a rental, and every few years for older homes with big trees. A camera inspection in Denver usually costs a few hundred dollars.
• Budget for repairs. Spot repairs often cost a few thousand dollars, while full line replacement can run well into five figures.
• Act fast on backups. Sewage entering the unit or non-working plumbing is a life, health or safety condition under Colorado's habitability law, so you must respond within 24 hours and start repairs within 24 hours. See our repair responsibilities guide.
• To report a backup you think is in the city main, call Denver Wastewater at 303-446-3400.

Radon: test, disclose and mitigate

Radon is a natural radioactive gas, and Colorado has a lot of it. The state health department classifies all 64 Colorado counties as EPA Zone 1, meaning a predicted average indoor level above 4 picocuries per liter (pCi/L), and estimates that about half of Colorado homes are above that level.

Landlord requirements (C.R.S. 38-12-803): before a lease is signed, you must give the tenant a written radon disclosure, which the tenant signs, including the state's radon warning, any known test results and mitigation history, and the state radon brochure. A tenant may void the lease if you didn't make the disclosure, or if you make no reasonable effort to mitigate within 180 days after a professional test shows 4 pCi/L or higher. From January 1, 2026, the voiding remedy doesn't apply to leases of one year or less, but the disclosure is still required.

What to do:

• Test the lowest livable level, and keep the results.
• If results are 4 pCi/L or higher, get a mitigation quote. The state health department estimates most homes cost $1,000 to $3,000.
• Disclose results and mitigation to every new tenant.

Lead: paint and water lines

Lead paint

Homes built before 1978 may contain lead-based paint. Federal law requires landlords of pre-1978 housing to give tenants a lead disclosure form, any known information about lead hazards and the EPA pamphlet "Protect Your Family From Lead in Your Home," and to include lead warning language in the lease.

When renovating, painting or doing make-ready in a pre-1978 home, use lead-safe practices and EPA-certified contractors for work that disturbs painted surfaces.

Lead service lines

Some older Denver homes still have lead water service lines, the pipe from the main to the house. These lines are customer-owned, but Denver Water's Lead Reduction Program, which started in 2020, replaces customer-owned lead service lines at no direct cost to the customer. Denver Water has replaced more than 35,000 lines and provides free water filters to affected households until six months after replacement.

Check your address on Denver Water's lead program pages, and tell tenants about the program and filter if your home is affected.

Old wiring and electrical panels

Knob-and-tube wiring

Knob-and-tube wiring was common from the late 1800s to the 1940s. It wasn't designed for modern electrical loads and has no ground wire. According to the International Association of Certified Home Inspectors, many insurance companies refuse to insure houses that have it, though some make exceptions when an electrician certifies the wiring as safe.

Problem panels

Federal Pacific Electric (FPE) Stab-Lok panels have a long history of breakers that may not trip. At least one insurer recommends all of them be replaced, and some insurers treat FPE, Zinsco and similar panels as ineligible.

What to do:

• Have a licensed electrician inspect any home built before about 1960, or any home with an unfamiliar panel.
• Ask your insurer directly whether your wiring and panel are acceptable.
• Budget to replace problem wiring and panels. Hazardous electrical conditions are a life, health or safety condition under Colorado law.

Swamp coolers

Many older Denver homes cool with evaporative "swamp" coolers instead of central air. Xcel Energy says they can use up to 75% less electricity than central air, and that they need maintenance every spring and fall.

Fall: shut off and disconnect the water supply line and drain it, drain the pan, cut power at the breaker and close or cover the unit. Do this before the first hard freeze.

Spring: reconnect, clean or replace pads, check the pump and belt, and confirm it works before the first hot week.

Colorado doesn't require air conditioning, but if you provide a cooler or AC unit, it's an appliance you must maintain. And you generally can't ban a tenant's portable cooling device. See our repair responsibilities guide.

Outdoor water: Denver's 2026 drought rules

Denver Water declared a Stage 1 drought in March 2026, and since October 1, 2026 has banned lawn watering and all spray irrigation until its board acts further. Trees, shrubs and perennials can be watered by hand with a shut-off nozzle or by drip. Fines for single-family customers start at $500.

Make sure your lease says who is responsible for landscaping and watering, and tell tenants about the current rules. Check Denver Water's site for updates before spring.

Older-home checklist for landlords

1. Camera-scope the sewer line.
2. Test for radon, and mitigate if 4 pCi/L or higher.
3. Prepare the radon disclosure and, if pre-1978, the lead disclosure and pamphlet.
4. Check Denver Water's lead service line status.
5. Have an electrician evaluate wiring and the panel.
6. Service the furnace, water heater and swamp cooler.
7. Confirm your insurer accepts the home's systems.
8. Build a capital reserve for the big items: sewer, roof, panel and HVAC.

How to get help

Older homes need a manager who knows them. Look for one who inspects with sewer lines, wiring, radon and lead in mind, keeps disclosure records for every lease and works with licensed plumbers, electricians and radon contractors. Ask how many pre-1980 homes they manage and how they bill vendor work.

We'll match you with vetted, licensed Denver managers. Free, no obligation. See what to look for in maintenance and inspections or get matched free.