Do You Really Need to Flush Your Tankless Water Heater? Everything Homeowners Should Know About Maintenance & Descaling

Why Tankless Water Heater Maintenance Matters More Than You Think

Tankless water heaters—also known as on-demand water heaters—are prized for their energy efficiency, compact size, and unlimited hot water. But just like a high-performance vehicle, they require regular maintenance to keep them operating at peak performance.

Unfortunately, many homeowners don’t realize that skipping tankless water heater maintenance can lead to reduced efficiency, mineral buildup, and even premature failure.

In this guide, we’ll walk you through:

• The difference between flushing and descaling

• Why maintenance frequency varies by model, usage, and water quality

• What manufacturers like Rinnai, Bradford White, AO Smith, and State recommend

• Why choosing a trained contractor like Denommee Plumbing, HVAC & Electric protects your investment

• How to text 857-226-9140 to book your service

Let’s get into it.

Flushing vs. Descaling: What’s the Difference?

If you’ve searched online about maintaining your tankless water heater, you’ve probably seen the terms “flush” and “descale” used interchangeably. But are they really the same thing?

💧 Flushing:

Flushing refers to circulating a cleaning solution (usually vinegar or a descaling agent) through the heat exchanger of your tankless water heater. This process helps remove mineral buildup, especially calcium and lime deposits that accumulate over time—particularly in homes with hard water.

⚠️ Descaling:

Descaling is essentially the goal of the flush. It’s the process of breaking down and removing scale deposits from inside the heat exchanger.

So yes—they’re related and often refer to the same maintenance task, but "descaling" describes the result, while "flushing" is the method.

Why Descaling and Regular Maintenance Are Critical

Unlike traditional tank-type water heaters that store hot water, tankless units heat water on demand by passing it through a series of internal coils (heat exchangers). Over time, minerals in your water (especially if you have moderately to highly hard water) begin to coat those coils, forcing the system to work harder.

Regular maintenance helps:

• ✅ Maintain energy efficiency

• ✅ Prevent overheating or system failure

• ✅ Extend the life of your unit

• ✅ Keep your warranty valid

• ✅ Improve flow rates and hot water delivery

Mineral scaling is the #1 cause of poor performance and early failure in tankless systems.

How Often Should You Flush or Descale Your Tankless Water Heater?

The answer depends on three key factors:

1. Water Quality

Homes with hard water (more than 7 grains per gallon of hardness) need more frequent flushing—often once per year, or even more often if mineral content is very high.

2. Usage Level

If you have a large household or high hot water demand (multiple bathrooms, laundry, dishwasher, etc.), your unit works harder and needs more frequent maintenance.

3. Manufacturer Requirements

Each brand and model has its own maintenance guidelines. Most recommend annual flushing, but some suggest intervals of 12 to 24 months depending on usage and water hardness.

Here’s a quick look at manufacturer recommendations:

How Is Professional Tankless Maintenance Done?

When you schedule service with Denommee Plumbing, HVAC & Electric, our licensed plumbers follow manufacturer-specific procedures for your unit, including:

1. System Evaluation – Inspect for error codes, water pressure issues, or poor flow

2. Flush and Descale – Using a pump and approved cleaning agent to safely remove scale

3. Filter Cleaning – Cleaning inlet screens and water filters

4. Air Intake Check – For models that require it

5. System Test – Confirm proper operation, hot water delivery, and diagnostics

6. Documentation – We can record service for warranty purposes

Why Choose Denommee for Your Tankless Water Heater Maintenance?

At Denommee Plumbing, HVAC & Electric, we’ve been helping homeowners across Massachusetts and southern New Hampshire get the most out of their tankless systems for over 25 years.

We’re Manufacturer-Trained Experts:

• ✅ Rinnai ACE PRO Contractor – The highest designation from Rinnai for training, performance, and service excellence

• ✅ Bradford White, AO Smith, and State Certified – We know the specs, service procedures, and warranty needs for all major brands

• ✅ Licensed plumbers – Not just HVAC techs doing plumbing on the side

• ✅ Proactive service reminders – We'll keep you on track for regular maintenance

• ✅ Hard water solutions – We can install filters, conditioners, or softeners to help protect your investment

From single-family homes to multi-unit properties, our techs deliver fast, friendly, and manufacturer-backed service that keeps your water heater running like new.

Signs It’s Time for a Flush or Descale

Even if your tankless system hasn’t failed, there are early warning signs that it may be time for maintenance:

• 🚿 Hot water takes longer to arrive

• 🚨 System shows an error code (like Rinnai code LC for “lime scale”)

• 🔥 Water isn’t staying consistently hot

• 💦 Noticeable drop in water pressure or flow

• 🔧 You can hear unusual sounds like popping or hissing

• 🛠 Maintenance has been skipped for 18+ months

Don’t wait for your tankless heater to fail. Catching scale buildup early is cheaper and far less disruptive than replacing a burned-out heat exchanger.

What About Flushing It Yourself?

It’s true—some homeowners do attempt DIY descaling using flush kits and vinegar. But there are important reasons to call a pro:

• 🧰 DIY may void your warranty if done incorrectly

• 🔌 Improper flushing can damage internal components

• 🚫 Using the wrong solution (like CLR) can corrode parts

• 📘 Manufacturer procedures vary widely—doing it wrong can cause more harm than good

• ⚡ You may overlook key steps like filter or air intake cleaning

When you hire Denommee, you get peace of mind, a valid service record, and a system that performs like it should.

📲 Text “Tankless Flush” to 857-226-9140 to Book Your Tankless Water Heater Service Today!

Whether your unit is overdue for a flush or you're just being proactive, Denommee’s licensed, manufacturer-trained techs are here to help.

Text us at 857-226-9140 or book online to schedule service in Massachusetts or Southern New Hampshire.

Areas We Proudly Serve

We provide expert tankless water heater maintenance and installation in:

• Massachusetts: Billerica, Burlington, Tyngsborough, Chelmsford, Westford, Acton, Tewksbury, Lexington, Bedford, Concord, Groton, Littleton, Dracut, Andover, and beyond

• New Hampshire: Nashua, Hudson, Brookline, Hollis, Londonderry, Pelham, Salem, Windham, and surrounding communities

As a locally trusted plumbing company, Denommee Plumbing, HVAC & Electric is committed to honest pricing, excellent service, and long-term relationships with our customers.

Final Thoughts

Tankless water heaters are efficient, convenient, and long-lasting—but only when they’re properly maintained.

• Flushing and descaling are essential, especially if you have hard water

• Maintenance requirements vary by brand, model, and usage

• Denommee is your trusted local expert, with manufacturer training from Rinnai, AO Smith, Bradford White, and State

• We handle everything, from descaling to diagnostics to annual maintenance plans

📱 Don’t put off your water heater flush. Text “Tankless Flush” to 857-226-9140 today and let Denommee help keep your system running smoothly.