How To Flush Rinnai Tankless Water Heater?

How To Flush Rinnai Tankless Water Heater


There are a lot of positives to having a tankless water heater, but the biggest advantage is how unlikely they are to corrode. The lack of tank means there is no build up of water, and therefore minimal corrosion.

They’re not just easier to take care of than more traditional water heaters, but they’re more durable too.

But while a tankless water heater is less likely to corrode than traditional water heaters, water can still cause mineral buildup over time. This mineral buildup will erode the walls of the heating chamber eventually, so regularly cleaning and getting rid of the mineral deposits ensures your tankless water heater runs smoothly.

You can even get away with cleaning your tankless water heater once a year, but this will depend on how hard the water is and what kind of Rinnai tankless water heater you’re using. But below we’ll get more into how often you should flush your Rinnai tankless water heater, as well as what the best way to clean it is.

What Is The Right Way To Clean A Rinnai Tankless Water Heater?

Although tankless water heaters are simple to maintain, it’s still important you clean them properly. There are 9 steps to cleaning your Rinnai tankless water heater properly and thoroughly. 

Turn The Power Source Off

If you have an electric Rinnai tankless water heater you will need to turn off the circuit breaker, and if you have a gas powered heater you just need to shut off the main gas.

Turn The Water Valves Off

There are three water valves connected to your Rinnai heater. While you’re cleaning it you don’t want cold water to enter the heater, and you don’t want hot water to leave. The cold water valve is usually blue, while the hot water valve is usually red. The third valve is the main valve that runs water into your home. 

Take A Look At The Purge Port Valve Caps

The purge valves should have small, T-shaped handles. You need to remove the caps slowly and carefully from the purge valves to release the pressure that’s built up inside the pipes. This will also reduce the risk of hot water coming out while cleaning the heater.

However, as the port valve caps are removed you can still expect some pressure. This is why it’s so important that the hot water valve is completely turned off, so you don’t burn your hands! You should also be careful to not move the rubber sealing discs, as they are needed for the valves to work. 

Connect The Hosing Line To All The Valves

Connect The Hosing Line To All The Valves

Not every manufacturer will include the hosing lines with the unit, but you can easily find them in home repair stores. The hosing lines need to reach between a bucket and your water heater. Consult the user manual for more information on flushing, or you can directly contact the manufacturer.

A sump pump will sometimes help connect the hoses to discharge. You may even flush the water from both the hot and cold water valves. It’s also important to remember to open the purge port valves! To open them you just turn them perpendicular to the position of the cold and hot valves.

Clean Your Tankless Water Heater

You can only clean your Rinnai tankless water heater with chemical solutions if you don’t use the water for drinking as these can be extremely dangerous if ingested. Undiluted white vinegar is a safe, natural cleaning solution and four gallons of water should be plenty. 

Consult Your User Manual

For the correct way to flush and drain your Rinnai tankless water, consult the user manual again. Every Rinnai tankless water heater is different, and therefore some may have different requirements for cleaning and flushing. You should be able to clean your tankless heater in 45 minutes. 

Close The Purge Port Valves

Once you’re done flushing the tankless water heater, you will need to twist the handles to close the purge port valves. You also need to disconnect and separate every hosing line from the valves. You should also return the purge port valves caps to the pipes.

The caps need to be tightened firmly, but make sure they’re not over-tight as this could damage the crucial rubber sealing discs.

Start The Unit Back Up

This will again involve consulting the manufacturer’s manual for more precise instructions on how to correctly restart your tankless water heater. You may have to rotate and open the cold and hot water valves, and these should be parallel to the main valve’s position.

Finish The Cleaning Process

You can now choose a faucet inside your home, and gently turn the hot water on. This allows more air to go through the pump. You should let it run until it can run regularly without air escaping. If you hear a soft sputtering sound this is a good sign, but you should allow the air pockets a couple of minutes to escape. 

How Often Will I Need To Flush My Rinnai Tankless Water Heater?

It’s important to keep your Rinnai tankless water heater clean by flushing it, and this should be done periodically to remove the mineral deposits that build up due to the hard water supply in the heater.

In the US, approximately 80% of customers use hard water for everything from showers to drinking water. So if you have a tankless water heater system you should flush your entire system at least once a year. However, some manufacturers recommend flushing the system out every six months, depending on how hard the water is where you live.

Final Thoughts

Tankless water heaters are designed to be low-maintenance and this is certainly the case with the Rinnai tankless water heater. It’s also fairly easy to flush out yourself at home, without needing to use specialist tools or calling in a professional. The Rinnai Tankless Water is designed for you to successfully flush and maintain at home.

But the main things to remember when cleaning your Rinnai Tankless Water Heater is to have the correct tools to hand, to consult the manufacturer’s instructions, and to be careful and safe.

YouTube video