Hot Water Recirculation Blog Image 02v2 02

December 2025
By: Josh Walejewski
Read Time: 2-3 Minutes

Tired of Waiting for Hot Water? Meet Hot Water Recirculation

If you’ve ever turned on a shower in the morning, watched cold water pour down the drain, and thought “there has to be a better way,” you’re exactly who this article is for.

As homes get bigger and plumbing runs get longer, that wait for hot water can feel endless, especially in a Wisconsin winter when the pipes can be much colder. Hot water recirculation systems (HWRS) are designed to tackle that problem head-on. Pair that idea with a modern tankless water heater, and things get really interesting.

Let’s walk through how hot water recirculation works, what it can do for your home, and why our plumbing team is often steering homeowners toward Rinnai’s RXSeries™ tankless units with built-in Smart-Circ™ Intelligent Recirculation™ instead of retrofitting an old tank.

The Everyday Problem: Cold Showers & Wasted Water

In a standard plumbing setup, your water heater keeps hot water ready in the tank. But the water sitting in the pipes between the heater and your fixtures cools off when no one is using it.

Result:
You turn on the tap and wait… and wait… and wait… while all that cooled water goes right down the drain before the hot water finally shows up.

Over the course of a year, that can add up to thousands of gallons of perfectly usable water wasted while you’re just “running it until it warms up.” Many manufacturers of recirculation systems estimate savings in the range of up to 10,000–12,000 gallons per year for a typical home.

How a Hot Water Recirculation System Actually Works

In a traditional plumbing setup, your water heater keeps a tank of hot water ready to go—but the water sitting in the pipes between the heater and your fixtures cools off between uses. That’s why you turn on the tap and watch cold water run for a while before it finally turns hot.

A hot water recirculation system (HWRS) changes that by turning your plumbing into a loop instead of a dead-end run.

Here’s the basic idea:

A small circulator pump is installed near the water heater. This pump’s whole job is to keep hot water moving gently through the hot water piping instead of letting it sit and cool.
Cooler water is sent back to the water heater. As water in the hot line cools down, the system moves that cooler water back toward the heater so it can be reheated, while fresh hot water is pushed out into the pipes.
Your pipes stay “primed” with hot water. Because the system is constantly cycling water through the loop on a schedule or based on temperature, hot water is already near your fixtures when you open a faucet or start a shower.
Smart controls keep it from wasting energy. Modern systems don’t just run the pump 24/7. They often use:
- - Timers (run during busy times, off when nobody’s using water)
  - Temperature sensors (circulate only when the water in the line drops below a set temperature)
  - Or “learning” controls that adapt to your household’s patterns and run the pump when you normally need hot water

The result is simple from a homeowner’s perspective:
You turn on the tap, and hot water shows up almost instantly. Leading to convenience, comfort, far less wasted water and dollars swirling down the drain while you wait.

Why Homeowners Love Hot Water Recirculation

Much shorter wait times for hot water
Showers, kitchen sinks, and bathroom faucets get hot water in seconds instead of minutes, especially in the areas farthest from the water heater.

Water savings
You’re not dumping cold water down the drain while waiting for hot water to “arrive.” Over time, that can mean thousands of gallons saved per year.

Convenience & comfort
Morning showers, dishwashing, and bedtime routines all get easier and less irritating—no more testing the water every 10 seconds to see if it’s finally warm.

The Retrofit Reality: Adding Recirculation to a Tank Water Heater

Here’s where things get a bit more technical—and where that “simple little upgrade” can become a bigger project.

Let’s say you have a standard tank-style water heater (natural draft or power vent), and you want to add a hot water recirculation system:

You need a circulator pump.
A pump like the Grundfos ALPHA HWR is mounted near the water heater, controlling when water circulates based on temperature or time.
You often need a return path.
- If your home already has a dedicated recirculation line from the farthest fixture back to the heater, great. The pump ties into that loop.
- If it doesn’t (which is most likely), you’ll need to run new piping for a dedicated return line.
Finished basement? Things get invasive fast.
Running new return line often means opening drywall, drilling through framing, and routing new vent and piping runs through finished spaces. Labor goes up. Mess goes up. Cost follows.

That’s exactly the kind of situation our Master Plumber ran into on a recent estimate.

A Real-World Example: When Tankless Was the Smarter Move

A homeowner recently called us out because they were interested in upgrading their natural draft tank water heater to a power vent, and adding a hot water recirculation system so they didn’t have to wait forever for hot water.

On paper, it sounded straightforward.

Then our Master Plumber walked the job.

The home had a finished basement.
Running a dedicated return line for a recirc loop would mean opening finished ceilings and walls.
Upgrading the water heater to a power vent would require new venting and additional retrofitting in those same finished areas.

By the time you add up the labor, patching, and disruption, the homeowner was staring at a big price tag for a “tank-plus-recirc-plus-venting” solution that still gave them a finite tank of hot water.

Instead, our plumber presented a better solution:

Swap the tank out entirely and install a Rinnai RX Series™ tankless water heater with Smart-Circ™ Intelligent Recirculation™.

Here’s why it made sense:

The Rinnai RX-Series has a built-in recirculation pump and Smart-Circ controls already inside the unit.
Using the existing cold water line as the return path (plus a recirc valve kit), we avoided running a dedicated recirc line through the finished basement.

The homeowner now gets:

Endless hot water (tankless doesn’t “run out” in the same way a tank does)
Much faster hot water at their fixtures
Smarter energy and water use thanks to Smart-Circ learning their patterns
Less invasive work in their finished spaces and lower long-term operating costs

In this case, switching to a tankless with built-in recirculation wasn’t just the “fancy” option—it was the practical one.

For many homeowners in southeastern Wisconsin, that package offers the best of both worlds: shorter waits, lower water waste, reduced water bills, and a water heater with a much longer lifespan than a traditional tanked water heater.

Thinking About a Water Heater Upgrade This Winter?

If your water heater is getting up there in age, or you’re tired of the “cold start” every time you turn on a tap, this is a great time to talk about:

Hot water recirculation options for your new or existing setup
Whether a Rinnai tankless with Smart-Circ™ Intelligent Recirculation™ makes more sense than putting more money into an old tank
What installation would realistically look like in your home—especially if you have a finished basement or tricky plumbing runs

Our plumbing team at Kettle Moraine Heating & Air Conditioning & Plumbing can walk through your home, evaluate your piping, and lay out the pros and cons of each path so you’re not guessing.

Kettle Moraine Plumbing Services is Here to Help

Reach out today and we’ll help you design a hot water setup that keeps your showers steamy, your mornings easier, and your water bill lower.

Contact Us