How to Clean Rinnai Tankless Water Heater

A Rinnai tankless water heater is a fantastic investment, providing endless hot water efficiently and reliably. To ensure it continues to operate at peak performance and to extend its lifespan, regular maintenance is essential. Over time, mineral deposits from your water supply, such as calcium and magnesium, can accumulate inside the unit’s heat exchanger. This buildup forces the system to work harder, reducing its efficiency and potentially leading to costly repairs down the line.

Fortunately, performing this routine maintenance is a straightforward task that most homeowners can handle. Learning how to clean Rinnai tankless water heater is a simple process of descaling, or flushing, the system. This guide will walk you through each step with clear, beginner-friendly instructions, helping you keep your unit in top condition.

Why Regular Cleaning of Your Rinnai Heater is Crucial

Regularly cleaning your Rinnai tankless water heater is vital for maintaining its efficiency and longevity. The primary reason for this maintenance is to remove sediment buildup and mineral scale that naturally accumulates inside the heat exchanger. This process, known as descaling, prevents the unit from overworking, which saves energy and lowers your utility bills. By investing about an hour each year in this simple task, you protect your appliance from premature failure, ensure a consistent flow of hot water, and avoid expensive service calls, making it one of the most important aspects of home maintenance.

8 Step-by-Step Guide: How to Clean Rinnai Tankless Water Heater

Step 1: Gather Your Supplies and Prepare for Safety

Before you begin the descaling process, you need to gather a few essential items. You will need a tankless water heater flush kit, which typically includes a small submersible pump and two hoses. You will also need a 5-gallon bucket and at least 4 gallons of undiluted white vinegar. It’s also a good idea to have some old towels on hand to catch any minor spills. For safety, it is critical that you turn off all power to the water heater at your circuit breaker. You must also shut off the gas supply by turning the valve handle perpendicular to the gas line.

Step 2: Isolate the Water Heater by Closing the Main Valves

Your Rinnai tankless water heater is equipped with a set of maintenance valves that make this process easy. Locate the three valves connected to your unit: a cold water inlet (blue handle), a hot water outlet (red handle), and the main gas valve (usually yellow). To isolate the unit from your home’s plumbing, turn the handles on both the cold and hot water valves so they are perpendicular to the pipes. This action stops water from entering the unit and from flowing out into your home’s pipes during the flushing process.

Step 3: Connect the Hoses to the Maintenance Valves

Now you will connect your flush kit hoses to the service ports on the maintenance valves. These ports have small T-shaped handles. Remove the caps from the purge ports on both the hot and cold water valves. Connect one of your hoses to the cold water valve’s service port. Place the other end of this hose into your 5-gallon bucket, securing the submersible pump to it. Connect the second hose to the hot water valve’s service port and place the other end of this hose into the bucket. Your setup will create a closed loop for the cleaning solution.

Step 4: Add Vinegar and Begin Circulating the Solution

With the hoses securely connected, pour the 4 gallons of undiluted white vinegar into the bucket. Ensure the submersible pump is fully submerged in the vinegar solution. Now, open the small T-shaped handles on both the hot and cold service ports by turning them parallel to the hose connections. This opens the service loop. Plug in the submersible pump to begin circulating the vinegar through the water heater. The solution will enter through the cold water port, flow through the heat exchanger, and exit through the hot water port back into the bucket.

Step 5: Let the Solution Circulate for Descaling

Allow the vinegar solution to circulate through the unit for at least 60 to 90 minutes. This circulation time is crucial for the acidic vinegar to effectively break down and dissolve the mineral and sediment buildup inside the heat exchanger. During this time, you might see the vinegar in the bucket become cloudy or notice small particles, which is a good sign that the descaling process is working. This flushing procedure is the core of how to clean Rinnai tankless water heater and restore its efficiency.

Step 6: Flush the System with Fresh Water

After the circulation is complete, unplug the submersible pump. Dump the used vinegar from the bucket and remove the pump from the cold water hose. Keep the hot water hose in the empty bucket. Close the cold water service port and open the main cold water valve slightly to allow fresh water to flow through the unit, flushing out any remaining vinegar and loosened debris. Let the fresh water run for about 5 to 10 minutes, or until the water coming out of the hot water hose runs clear and no longer smells of vinegar.

Step 7: Return the System to Normal Operation

Now you can restore your system to its normal operational state. First, close the main cold water valve again. Then, close the hot water service port and remove both hoses. Replace the caps on the service ports securely. Open the main hot and cold water valves by turning their handles parallel to the pipes. At this point, it is critical to clean the small inline filter on the cold water inlet to remove any dislodged debris before restoring power. This final check is an important part of knowing how to clean Rinnai tankless water heater completely.

Step 8: Restore Power and Gas

With the plumbing returned to normal, you can now restore the gas and power. Turn the gas valve handle parallel to the pipe to reopen the gas supply. Then, go to your circuit breaker and switch the power back on for the water heater. Turn on a hot water tap in your home to ensure everything is working correctly. The water may sputter at first as air is purged from the lines. Let it run until you have a steady stream of hot water. Congratulations, you have successfully cleaned your unit.

Additional Tips for Maintaining Your Water Heater

• Regularly check and replace the anode rod in your water heater. This component plays a crucial role in preventing corrosion within the tank, which can lead to leaks and other issues.
• Consider installing a water softener if you have hard water. Hard water contains high levels of minerals that can build up in your water heater, reducing its efficiency and lifespan.
• Flushing your water heater once a year is recommended to remove sediment buildup and maintain its efficiency. You can do this by attaching a hose to the drain valve at the bottom of the tank and draining out the water until it runs clear.
• Insulate your hot water pipes to reduce heat loss and save energy. This will also prevent your pipes from freezing during winter.
• Consider upgrading to a tankless water heater for a more efficient and space-saving option. These heaters only heat water when it is needed, avoiding the need for a large tank of constantly heated water.

Frequently Asked Questions

How Often Should I Clean My Rinnai Tankless Water Heater?

Rinnai recommends cleaning your tankless water heater at least once a year. However, if you live in an area with very hard water (high mineral content), you should consider descaling your unit every six to nine months. Regular cleaning is the best way to maintain efficiency and prevent long-term damage from mineral buildup, ensuring the longevity of your appliance.

Can I Use Something Other Than White Vinegar?

While white vinegar is the most common, affordable, and safe solution for DIY cleaning, you can also use a commercially available descaling solution specifically designed for tankless water heaters. These solutions are highly effective but may be more expensive. It is important to avoid using harsh chemicals that are not approved for potable water systems, as they can damage the internal components of your heater.

What Is a Rinnai Error Code 11?

An Error Code 11 on a Rinnai unit typically indicates an ignition failure. While this can be caused by several issues, a common culprit is a blocked or dirty gas burner or a clogged heat exchanger, which can be related to a lack of maintenance. Regular cleaning helps prevent the buildup that can contribute to such errors. If cleaning does not resolve the issue, it may indicate a problem with the gas supply or an internal component, requiring a professional service call.

Is a Tankless Water Heater Flush Kit Necessary?

Yes, a flush kit is highly recommended and makes the process significantly easier and safer. The kit provides the necessary components—a submersible pump and hoses—to create a closed loop for circulating the cleaning solution. While you could assemble these parts individually from a hardware store, purchasing a kit ensures you have the correct fittings and a pump designed for this type of task.

Do I Need to Clean the Inlet Water Filter?

Yes, cleaning the inlet water filter is a crucial step that should not be skipped. This small, screen-like filter is located on the cold water inlet pipe and is your unit’s first line of defense against sediment and debris. After flushing, this filter can catch particles dislodged from the heat exchanger. Cleaning it prevents this debris from re-entering the unit or clogging your home’s fixtures.

Conclusion

Knowing how to clean Rinnai tankless water heater is a valuable skill for any homeowner, empowering you to maintain your appliance for optimal performance and a long service life. By following this straightforward descaling process, you can prevent the harmful effects of mineral buildup, ensuring your unit runs efficiently and reliably for years to come. This simple annual maintenance is a small investment of time that pays significant dividends in energy savings and avoided repair costs.

Don’t let simple maintenance intimidate you. With this guide, you are fully equipped to handle this task with confidence. Take pride in protecting your investment and enjoy the peace of mind that comes with a well-maintained, high-performing water heater.