How to flush your tankless water heater

On this blog, we’ve previously covered how to flush a standard water heater, but we’ve been recently getting questions from homeowners on a related subject: flushing a tankless water heater. Since most homeowners with tankless systems are still pretty new to them, many of us are unsure about whether or not these demand-type systems even require flushing. The answer is “Yes,” and we’re going to tell you how to do it.

In this article, we’ll take you through the steps of flushing a tankless water heater and help you decide if this is a project you can take on yourself, or need to bring in a plumber to help you complete. Along the way, we’ll discuss why tankless water heaters require this kind of annual maintenance and how skipping it could result in a premature end for your system.

Does my tankless water heater require maintenance?

Every homeowner knows that a traditional water heater—picture the unit with a storage tank—requires annual maintenance in the form of draining and flushing the system. With a traditional water heater, this helps prevent mineral buildup from negatively impacting the system’s performance and overall lifespan. What most homeowners don’t know, however, is that tankless water heaters require the same level of care. If you’ve had a tankless water heater installed in your home, you need to make sure it gets an annual checkup.

Related: Everything you need to know about tankless water heaters

Flushing your tankless water heater

Flushing a tankless water heater is a bit different from flushing a traditional system. Here’s a key difference: unlike draining and flushing a traditional water heater—which almost any homeowner can do with just a few basic tools—you’ll typically need some specialized equipment to clean out your tankless system.

Some manufacturers and retailers sell what’s called a “tankless water heater flushing kit” which includes hoses, buckets, and—most importantly—a circulation pump to force the cleaning solution through the inner pipes of the system. These kits typically retail for about $125 – $175, but they’re absolutely essential to doing this process safely.

First, you’ll need to turn off both of the water intake valves (hot and cold) to your water heater. As a safety precaution, you should also turn off the gas or electric connection to depower the unit. Next, connect the hoses that came with your flushing kit to the water heater’s inlet and outlet valves. Make sure these hoses are firmly attached, but don’t over tighten them—you will want to be able to get them off the unit when you’re done, after all.

Follow the instructions in the kit to attach the circulation pump to the inlet hose. Similarly, place the other end of the outlet hose in either the bucket that came with a kit or a large, watertight container you have around your home. Fill that bucket or container with water and the specialized cleaning chemical that came as part of the kit. If your kit didn’t come with any chemical, you can use vinegar, but avoid using any other types of chemicals, as they may interact unpredictably with your system.

Once you’ve got everything set up, open the water valves and start the circulation pump. The amount of time you need to let everything circulation depends on what cleaning chemical you’re using, so check with the instructions before you get started. On average, this process will take anywhere from an hour to two hours to complete, so make sure you leave yourself enough time to let the cleaning process run its course.

When time’s up, stop the pump and close off the valves. You’ll want to complete the “flush” part of the process by turning on the cold water intake valve and allowing tap water to move through the system. You should give this 5-10 minutes to complete before you once again turn off that intake valve, disconnect the remaining hoses that came with your kit, and then turn everything back on—including the intake valves and the power. You’ve now successfully flushed your tankless water heater.

Watch: Flush your tankless water heater

In this video, you’ll see the exact steps you need to follow in order to flush your home’s tankless water heater.

Do you need to hire a professional?

While a tankless water heater flush can be a DIY project, that really depends on how comfortable you feel following the steps above to flush your tankless water heater. It’s also worth noting that even a DIY project comes with built-in costs, as you’ll need to purchase a cleaning kit to even get started, and continue to purchase cleaning fluid every year to flush out the system. If that sounds like a major hassle, you’re probably better off having our plumbers handle this process for you.

One of the other benefits of having a Wagner plumber out to your home to flush out your water heater is that it gives us a chance to check on the overall condition of the system. You’ll also have the comfort and confidence of knowing that a professional did the job right and your tankless water heater is set for another year of high-performance heating.

Whether you opt to do this work yourself or bring in one of our pros to help out, make sure that you do something. A tankless water heater that doesn’t get flushed out annually won’t last as long as one that does, and it’ll probably start to perform worse as it ages. That might not sound like a big deal now, but you don’t want to be kicking yourself years down the road for skipping this critical maintenance. Make sure you invest in the long-term “health” of your water heater by picking a date on your calendar to do this work.

Related: Your guide to maintaining your water heater

Call Wagner for tankless water heater maintenance

Our friendly and professional plumbers are ready to help you maintain your tankless water heater. If yours is overdue for a flush, there’s no better time than the present to contact us and schedule a tankless water heater checkup and flush.