Tankless Water Heaters in Austin & San Antonio

Hot Water That Does Not Run Out

Tankless water heater installation, repair and annual descaling for Austin, San Antonio and Central Texas homes. Sized for the way your household actually uses hot water, with our hard water planned for from day one.

Tankless Water Heaters

Endless Hot Water, If the Install Is Done Right

A tankless water heater heats water as it passes through, so there is no tank to empty and no forty gallons being kept hot all night for nobody. When the last person in the shower line gets water as hot as the first, that is the tankless promise, and it is real. The catch is that the unit only delivers it when it is sized correctly and installed with the gas supply, venting and water treatment it needs. A lot of the tankless complaints we hear about are not tankless problems. They are installation problems.

Radiant sizes by flow rate and temperature rise, not by square footage. In Central Texas the incoming water is warm most of the year, which works in a tankless unit’s favor, but a January morning after a cold front asks a lot more of it. We size for the cold months. We also upgrade the gas line when the existing one cannot feed a unit that draws several times what a tank does, run the venting the manufacturer specifies, and talk honestly about hard water, because scale is what shortens a tankless unit’s life here. Pairing it with a softener or conditioner and an annual descale is how you get the long service life the brochure promises.

If a standard tank replacement is the better fit for your house and budget, we will tell you that too. Every install is backed by the Home Comfort Guarantee, and financing is available.

  • Sized for winter, not July Flow rate and temperature rise calculated for the coldest incoming water you will see, so it keeps up in January.
  • Gas and venting done properly Gas line capacity, venting and condensate handling to the manufacturer’s spec, which is what the warranty depends on.
  • Hard water planned for Isolation valves for descaling on every install, and a straight answer about whether you need a softener.
Radiant plumber with a tool bag beside a service van before a tankless water heater installation

Is Tankless Right for You?

When a Tankless Water Heater Makes Sense

It is not for every house. These are the homes where it earns its price.

  • Back-to-back showers run cold

    A busy household that empties a tank every morning is the classic case for on-demand hot water.

  • A big soaking tub or multi-head shower

    Fixtures that draw more than a tank holds. A properly sized tankless unit fills them without a wait.

  • The tank lives in the attic

    A wall-hung tankless unit takes forty gallons of water out from above your ceiling.

  • Long stretches with nobody home

    No standby heat loss. If the house sits empty, the unit sits idle instead of reheating a tank all day.

  • You need the closet back

    A tankless unit hangs on a wall, indoors or out, and frees the floor space a tank was taking.

  • The old tank is due anyway

    The best time to price a tankless conversion is when you are already replacing the tank, not the week after.

What We Do

Tankless Installation, Repair and Service

The whole job, from the gas meter to the isolation valves, by one licensed crew.

A full house of family and guests at home, the kind of household a tankless water heater is sized for
Tankless water heater installation, repair and service.
  • New tankless installation Gas or electric units, indoor or outdoor models, sized and mounted where the venting and drain work.
  • Tank-to-tankless conversion Removing the tank, upsizing the gas line, running new venting and condensate, and pulling the permit.
  • Gas line upgrades A tankless burner draws far more gas than a tank. We size the line so the unit gets what it needs at full demand.
  • Recirculation systems Built-in or add-on recirculation so the far bathroom gets hot water quickly instead of running the tap for a minute.
  • Tankless repair Error codes, ignition faults, flow sensors, fans and the inlet filters that scale and debris clog.
  • Annual descaling Flushing the heat exchanger with descaling solution through the isolation valves, and cleaning the inlet screen.

How It Works

How a Tankless Installation Goes

A conversion is a bigger job than a tank swap. Here is what that looks like.

  1. We look at the house

    Fixtures, how many run at once, the gas meter and line size, where the unit can vent, and where condensate can drain.

  2. We size and price it

    Flow rate and temperature rise for winter, a unit that meets it, and a written quote including any gas or venting work. Honored for 72 hours.

  3. We install to spec

    Gas, venting, condensate, isolation valves and the permit. The install is what the manufacturer’s warranty depends on, so it is done their way.

  4. We test and walk you through it

    Full-demand test with multiple fixtures running, temperature set, and a quick lesson on the display, the filter and the descaling schedule.

Tired of the Shower Going Cold?

Get a written tankless quote, with financing available and no pressure to decide on the spot.

What Our Customers Say

Don't just take our word for it — hear from our satisfied customers

J Jeff Fazio
Jeff Fazio 3 years ago
★★★★★
I had Radiant Plumbing replace my tankless water heater, damaged in the Feb. 2021 snowmageddon storm with a new unit. The process was smooth and professional from start to finish. The plumber, James, was extremely knowledgeable and thoroughly explained my options to me. The cost and time to perform the installation were just as estimated. When he was done, James explained how to maintain the system, what service would be needed and how to perform it, and answered all of my engineering geek questions. It was a thoroughly positive experience. I have used several different plumbers in Austin over the past 15 yrs, but my search is over - I will not hesitate to call Radiant next time and would recommend them unreservedly.

8/9/23 Update: I have subsequently used Radiant for a toilet repair, faucet installation (Danny), and drain work (Ezekiel) and they have continued to impress with knowledgeable, friendly plumbers and quality work.
C Cathy McClaugherty
Cathy McClaugherty 5 years ago
★★★★★
We called Radiant Plumbing after we noticed a water leak in our kitchen. We were in a time crunch and they were able to schedule us quickly, before we left for vacation. They sent their representative, Preston Nichols, and he was excellent to deal with! He was on time, skillful, friendly, and very professional. It turned out to be a problem with our dishwasher but Preston was quick to diagnose it and set our minds at ease. While he was here, we mentioned that our one year-old water heater needed to be flushed. Preston was quick to take care of that, as well, saving us time and money in the process. Radiant charged us almost half the price another plumber quoted us for that service! While Radiant Plumbing isn’t our usual plumber, they gained a new customer. We won’t hesitate to call Radiant again in the future based on our VERY positive experience with them.
S Stefano Rosellini
Stefano Rosellini 6 years ago
★★★★★
Had 3 different systems installed by them approx. 3 years ago for a total of approx $20k. I was quite happy with the install until the year later when they came for a maintenance call and started finding deficiencies in their own install. they wanted extra money to address those deficiencies. Now I am in the process of selling my home and an inspector has found a few items that need to be addressed and they will not even look at the report unless I schedule a $139.00 service call. Very poor customer service.. This company does not stand by their work and would not recommend.

I am revising my review of this business from 1 to 5 stars. After my original review I was contacted by the company's service manager and he made sure that I was taken care off. I had a team of 3 technicians coming to my house to double check the system and make the necessary adjustments. I was very satisfied by their attention to details and professionalism.

Maintenance Membership

Join the Care Club

Home maintenance for $9.99 a month.

Care Club members get two HVAC tune-ups and a plumbing safety inspection every year, priority scheduling, no dispatch fees — ever — and 5% off every repair.

  • Priority scheduling
  • Seasonal HVAC tune-ups
  • Annual safety inspection
  • Exclusive member discounts
  • Free dispatch on repairs
  • No long-term contracts

Tankless Water Heater Questions

Will a tankless water heater work with our hard water?

Yes, with two conditions. Hard water leaves scale inside the heat exchanger, where the water passes through narrow passages that are heated hard and fast. Left alone, scale insulates the exchanger, drops efficiency, triggers error codes and eventually damages the unit. The first condition is annual descaling, which is why we install isolation valves on every unit so it can be flushed without disassembly. The second is a serious look at water treatment. A softener ahead of the tankless unit removes the problem at the source, and in San Antonio’s especially hard water we consider it close to mandatory for a long service life. A salt-free conditioner is a lighter-touch alternative that reduces scale adhesion.

How is a tankless water heater sized?

Two numbers: flow rate and temperature rise. Flow rate is how many gallons per minute of hot water you need at once. A shower, a kitchen sink and a washing machine running together add up quickly. Temperature rise is the difference between the incoming cold water and the hot water you want at the tap. In Central Texas that rise is small in summer, when the ground water is warm, and much larger after a winter cold front. A unit sized for July will disappoint you in January, so we size for the cold months. If your peak demand is high, one large unit or two smaller ones in tandem both work, and we will price whichever fits the house better.

Can I switch from a tank water heater to tankless?

Almost always, but it is more than a swap. A gas tankless unit draws several times the gas of a tank heater at full fire, so the gas line from the meter often needs to be upsized, and sometimes the meter does too. The venting is different and specific to the unit, and a condensing model needs a drain for the acidic condensate. The unit needs a wall location that satisfies all three. Electric tankless units avoid the gas and venting but need a large amount of electrical capacity, which not every panel has. None of that is a reason not to convert; it is the reason a proper quote covers the whole job rather than the box on the wall.

Does a tankless water heater need maintenance?

Yes, and skipping it is the main reason tankless units fail early here. Once a year the heat exchanger should be descaled by circulating a descaling solution through it via the isolation valves, and the inlet water filter and any air intake screen should be cleaned. On a unit fed by softened water the scale builds much more slowly, but the annual check is still worth it for the filter, venting, condensate drain and a look at the error history. We can handle it as part of water heater maintenance, and Care Club members get no dispatch fees and 5% off any repair we find.

Will I still wait for hot water at the far bathroom?

Yes, unless recirculation is part of the plan. A tankless unit heats water on demand, but that water still has to travel through the same pipes as before, so the far bathroom waits just as long, and sometimes a few seconds longer while the burner lights. The fix is a recirculation system, either built into the unit or added as a small pump and return line, which keeps hot water near the fixtures on a schedule or on demand. It adds cost and a little energy use, so we only recommend it where the wait is genuinely annoying, typically a large single-story home with the unit at one end and the primary bath at the other.

*Offers cannot be combined with other promotions or applied to dispatch fees. No cash value. Must present offer at time of service. Call for details.
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