Residential plumbing · Thornton, Colorado

24-Hour Emergency Plumber in Thornton & the Denver Metro

Colorado Plumbing Contractor Registration #PC.0005836 · Master Plumber License #03002471

Water heaters, tankless, fixtures, leaks, gas lines and whole-home water filtration for homes across the Denver Metro, from Castle Rock to Longmont. Call any time a pipe bursts or a water heater lets go, or book a regular visit online.

Call (303) 472-4368 Schedule Service

Two gas tank water heaters installed side by side in a utility room, each with a blue thermal expansion tank, copper water piping and metal vent pipes rising to the ceiling.

Water leaking right now?

Shut off the main water valve if you can, then call. We answer emergency calls around the clock.

Call now (303) 472-4368 Send an urgent request

Licensed Master PlumberColorado license #03002471
Locally owned in ThorntonJohn's company, John's license
24-Hour Emergency ServiceBurst pipes, leaks, water heaters
One callWater heaters, fixtures, leaks, gas & filtration

Services

What we work on

Plumbing for homes, done properly, plus help when a pipe lets go. Light commercial jobs are considered case by case. Call to ask.

Water Heater Repair & Replacement

Tank water heaters that leak, run out of hot water or won't light. Repaired when it makes sense, replaced when it doesn't.

Tankless Water Heaters

Wall-mounted tankless installs sized for Colorado winters, plus repair and descaling for the units you already have.

Faucets, Toilets & Fixtures

Dripping faucets, running toilets, tired shower valves and new fixtures you've picked out.

Leak & Pipe Repair

Pinhole leaks, failed fittings, frozen and split pipes, leaking shutoff valves and supply lines.

Whole-Home Water Filtration

Whole-house filtration and scale control installed where water enters your home, including HALO systems.

Gas Line Repair

Leaking gas valves and fittings, damaged gas pipe, and gas lines for water heaters and tankless units.

24-Hour Emergency Plumbing

Burst pipes, active leaks and water heater failures that can't wait.

Not sure what it is?

Water where it shouldn't be, a strange noise, a cold shower. Call and describe it. We'll tell you plainly whether it's something we handle.

Call (303) 472-4368

Special offers$60 off any plumbing repair and more. Mention it when you book.

See offers

Water filtration

Whole-home water filtration

A whole-home system filters water where it comes into the house, so every faucet, shower and appliance gets treated water. It also cuts down on scale in your water heater and fixtures.

We install whole-house systems, including systems from HALO Water Systems, sized to your home. $500 off a whole-home water filtration system.

Water filtration Schedule Service

HALO systems we install

Recent work

Photos from John's jobs: water heaters, filtration systems and copper piping.

Copper line with a brass valve and fittings running up the outside wall of a house above a rock bed.

White PVC drain and vent piping with purple primer marks, hung from metal straps along a basement ceiling.

Two tank water heaters side by side in a utility closet, each with a blue expansion tank and copper piping overhead.

Vertical copper water piping with red-handled ball valves and brass fittings, mounted on a board against a wall.

Tank water heater installed next to a furnace in an unfinished basement, with copper and PVC piping.

Copper water piping with a brass pressure reducing valve and red-handled ball valves against a concrete wall.

Tank water heater in a basement with white PVC vent piping overhead and an expansion tank above it.

Grey whole-home water filtration tank and filter housing connected to copper piping in an unfinished basement.

Stainless steel HALO whole-home water treatment tank with its control head, connected by copper bypass piping.

New copper water piping roughed in with a brass valve inside an open wood stud wall.

Stainless steel whole-home filtration tank next to a newly installed tank water heater with a blue expansion tank.

White wall-mounted tankless gas water heater in an unfinished basement, with copper water connections and a yellow gas line below, white PVC vent pipes and red and blue PEX lines overhead.

Hot water

Tank or tankless, set up for Colorado

Most calls we get start with hot water. A tank that's leaking, a pilot that won't stay lit, a shower that goes cold halfway through.

At Front Range elevations, gas burns with less oxygen, and winter supply water comes in cold. Since January 2026, Colorado's HB23-1161 also sets low-NOx limits on most new gas water heaters. All of that affects how a water heater should be chosen, vented and set up, whether we're repairing a tank, replacing one, or installing a tankless unit like the one pictured.

Water heater repair and replacement · Tankless water heaters · Tank vs. tankless in Colorado homes

Before you call

Three things that make the call faster

None of these are required. They just help us understand the problem before we arrive.

Know where your main shutoff is

Usually where the water line comes into the house: a basement wall, utility room, crawl space or garage. If water is leaking, close it first.

What to do about a burst pipe

Read the water heater label

The sticker on the side lists the brand, size, and gas or electric. The serial number usually encodes the year it was made.

Signs it's time to replace

Snap a photo

A picture of the leak, the fixture, or the equipment label tells us a lot. You can add it when you book online.

Who you're hiring

Owned by a Colorado Master Plumber

Underhill Plumbing Services is owned by John Kuykendall, who holds Colorado Master Plumber License #03002471. Colorado licenses plumbers through the Department of Regulatory Agencies (DORA), and you can look up any plumber's license on DORA's website.

We're a new company, so we'd rather show you our work than make big claims. The photos on this site are from real jobs.

About John and the company · Licensing details

Service area

Based in Thornton, working across the Denver Metro, from Castle Rock in the south to Longmont in the north.

See the full service area

From the blog

Call, book online, or send a message.

The fastest way to reach us is a phone call: (303) 472-4368. To pick an arrival window, use online scheduling. Or send a message and we'll get back to you.

Hours7 AM to 9 PM, every day
Emergencies24-hour emergency service for burst pipes, leaks and water heater failures.

What to do in a plumbing emergency

Send us a message

Tell us what's going on and we'll get back to you. For anything urgent, call (303) 472-4368. To pick a time, use online scheduling.