How to Flush a Tankless Water Heater Safely Without Damaging the Unit
Before explaining how to flush a tankless water heater, it helps to know why the job matters. Over time, minerals like calcium and magnesium build up inside your unit, especially if your home has hard water. These mineral deposits, or “scale,” can coat the heat exchanger and make your system work harder to heat water.
At Drake Plumbing, we’ve seen firsthand how this buildup affects performance. A layer of scale doesn’t just reduce efficiency — it also shortens the lifespan of your water heater and can even lead to costly repairs if ignored.
If left unchecked, this buildup can cause poor water pressure, inconsistent hot water, and higher energy bills. Regular tankless hot water heater maintenance with Drake Plumbing helps prevent those issues. Flushing your system once a year can clear out the scale and keep your water heater running smoothly.
Tools and Materials You’ll Need to Flush a Tankless Water Heater
Before starting, gather the right tools to make the process simple and safe.
Here’s what you’ll need:
- Two garden hoses: These will connect to the service valves to circulate the cleaning solution in and out of the heater.
- A submersible pump: This pump moves the vinegar through your system to clean the heat exchanger.
- A five-gallon bucket: This holds the vinegar and collects the water during the flush.
- Four gallons of white vinegar: Vinegar is a safe and effective cleaner for dissolving scale without harming your heater.
- A screwdriver: You’ll use this to open the access panels and service valves.
Having these items ready before starting ensures you don’t have to pause halfway through the process.
Step-by-Step Guide on How to Flush a Tankless Water Heater
Knowing how to flush a tankless water heater the right way helps prevent damage to delicate parts. Here’s a clear, simple breakdown of each step:
1. Turn Off the Power and Water Supply
Start by shutting off the power to the water heater. For gas models, turn the gas valve to the “off” position. For electric models, flip the circuit breaker off. Then close the cold and hot water isolation valves on your tankless unit. This keeps water from entering or leaving during the flush.
2. Attach the Hoses
Connect one hose to the cold-water service port and the other to the hot-water port. Run the cold-water hose into your vinegar bucket and attach the submersible pump to it. The hot-water hose will drain the vinegar back into the bucket. This creates a loop so the cleaning solution can circulate through the heater.
3. Circulate the Vinegar
Turn on both service valves and switch on the submersible pump. Let the vinegar circulate for about 45 minutes to an hour. This step helps break down the mineral buildup inside your unit. You might hear light bubbling as the vinegar reacts with the scale, which is normal.
4. Rinse the System
After about an hour, turn off the pump and close the service valves. Remove the hoses and empty the bucket. Then, open the cold-water valve to flush clean water through the system for about five minutes. This step clears out any leftover vinegar and loosened debris.
5. Restore Power and Water
Once you’ve flushed the unit, close the service valves and open the hot and cold-water isolation valves. Restore power to the heater. Run a few taps around the house for several minutes to make sure hot water flows consistently again.
Common Mistakes to Avoid During a Tankless Water Heater Flush
Even a small mistake during tankless water heater flush can cause problems later. Here are a few things to watch out for:
- Skipping the power shut-off: Running the pump while your system is on can damage the heating elements or trigger safety sensors.
- Using harsh chemicals: Stick with vinegar, as stronger cleaners can corrode parts inside the heater.
- Not rinsing afterward: Failing to rinse thoroughly can leave residue inside the system, leading to odours or performance issues.
- Flushing too often or too rarely: Once a year is ideal for most households. Homes with hard water may need a flush every six months.
Signs Your Tankless Hot Water Heater Needs Maintenance
It’s easy to forget about your water heater until something goes wrong. Knowing the early warning signs can help you stay ahead of costly repairs.
Watch for:
- Fluctuating water temperature: If the water turns cold suddenly, scale buildup might be restricting flow through the heat exchanger.
- Low water pressure: Minerals can block the narrow pipes and valves that move water through the system.
- Unusual noises: Popping or rumbling sounds often point to mineral deposits inside the heater.
- Error codes: Many modern units display a maintenance code when they detect flow problems.
If you notice any of these symptoms, it’s time to perform a tankless water heater flush or schedule professional service.
How Professionals at Drake Plumbing Handle a Tankless Water Heater Flush
Flushing your unit yourself can save money, but it’s easy to make mistakes that shorten your heater’s lifespan. At Drake Plumbing, our trained technicians perform full tankless hot water heater maintenance using professional tools and safety procedures.
Our plumbers inspect every connection, check for leaks, and clean the internal components without voiding your manufacturer’s warranty. We handle service for all major brands and models. Whether you’re looking for a plumber in Madisonville, LA, Mandeville, LA, Covington, LA, Hammond, LA, or Ponchatoula, LA, our team is ready to help. We even cover wider areas like St Tammany Parish.
How Often Should You Flush a Tankless Water Heater?
For most homes, once a year is enough to keep the system clean. If your area has hard water, every six months may be better. Regular flushing keeps your unit efficient and helps it last longer. Skipping this maintenance can lead to costly repairs or full replacements years earlier than necessary.
The U.S. Department of Energy recommends regular water heater maintenance to maintain efficiency and extend service life.
Contact Drake Plumbing for Water Heating Solutions in Louisiana
Learning how to flush a tankless water heater safely is a great way to protect your investment and keep your hot water running strong. Still, if you’d rather skip the mess and risk, the team at Drake Plumbing is here to help.
Our licensed plumbers provide reliable tankless hot water heater maintenance across Louisiana and guarantee the job is done right the first time.
Call us today at 985-703-0477 or reach out through our contact page to schedule your tankless water heater service or any plumbing repair. Regular maintenance keeps your system clean, efficient, and ready to deliver endless hot water year-round.
FAQs About How to Flush a Tankless Water Heater
1. Can I use something other than vinegar to flush my tankless water heater?
It’s best to use white vinegar. It’s safe, affordable, and won’t harm the internal components. Avoid harsh descalers unless approved by your heater’s manufacturer.
2. What happens if I never flush my tankless water heater?
Over time, mineral deposits will reduce water flow and strain the heating elements. This can cause inconsistent temperatures and even trigger error codes or complete failure.
3. Is flushing the heater difficult?
It’s not overly complicated, but it does require attention to detail. Missing a step or using the wrong setup can lead to leaks or electrical issues.
4. How long does a professional flush take?
A trained plumber can usually complete a flush in about one to two hours, depending on the buildup and condition of the unit.
5. Can Drake Plumbing help with other plumbing needs?
Yes, our services cover everything from drain cleaning and leak repair to fixture installations and full plumbing upgrades.
