How to Flush a Rheem Tankless Water Heater

How to Flush a Rheem Tankless Water Heater

  • If you’ve always wanted to know how to flush a Rheem tankless water heater, here’s your chance! This article explores all the steps to getting your Rheem tankless water heater flushed easily.

What makes a home modern in the world we live in today? Is it defined by the number of chic pieces of furniture in the living room? The automation of voice control that makes you say a word, and your window blinds open up? Or the number of smart and modern appliances found in the home? If your answer combines everything, you’re not far from the truth.

Even if you don’t want to join the trend and the modest part of you wants to stay away from the modern trends, there are things in the house you can’t do without – the water heater is one of them. Rheem has done incredibly well in the market of tankless water heaters. While its tankless water heaters are arguably the best in the market, they must be regularly maintained to keep them working as intended.

Worth Reading: How to Flush a Navien Tankless Water Heater?

Suppose you own a Rheem water heater; good for you. However, we thought you could find a piece on how to flush a Rheem tankless water heater helpful, which is why we’ll be walking you through the steps you must take to flush your tankless water heater. Let’s delve right into these steps!

Get Your Supplies Ready

Nobody goes to war without some ammunition in their arsenal, so if you’re flushing your Rheem tankless water heater, you must gather the right supplies to make the process seamless. Thankfully, the supplies needed for your Rheem tankless water heater maintenance are very basic – these are things you can easily find around the house, except a few. Here are some of the essential supplies you must have:

NOTE: The first thing you should try to get is the Rheem flush kit for tankless water heaters. It usually contains everything you’ll need to flush your water heater. However, in the absence of the kit, you can improvise with the ones we’re listing below.

  1. Bucket: Almost every household maintenance task requires a bucket, and flushing your water heater is no exception. A 5-gallon bucket will do the job. You only need it to collect water or anything else. Its goal is to help keep things tidy.
  2. Towels: Since you’re dealing with a water heater, it’s only normal for splashes to fly around, so one must be prepared for them by having a couple of towels.
  3. Flushing pump: A flushing pump is very crucial for this flushing task. It will help circulate your cleaning solution through the water heater. It may be little, but its importance cannot be overemphasized.
  4. White vinegar: White vinegar is the best cleaning agent for this job. It is always very quick to dissolve mineral deposits and other contaminants.
  5. Hand gloves: Hand gloves are essential for this maintenance task because they protect your hands. Since you will be dealing with hot water, you should opt for heat-resistant gloves. That way, you can keep your hands safe from burns.
  6. Hoses: Hoses are also needed to flush your water heater. You must attach the hoses to both ends of the water heater – entrance and exit. If you have garden hoses, you can use them. They will work just fine.

Put Safety Precautions in Place

Safety might not be the first thing that comes to mind when you embark on a cleaning journey, but it’s something no one should ever take for granted. So as part of the Rheem water heater flushing instructions, let’s explore some of the safety precautions one has to take below:

Turn off the water heater

Starting the flushing process of your water heater without first turning it off is risky – it most likely will result in an accident. To avoid such a scenario, you must turn off the unit before attempting maintenance. Turning off the unit and disconnecting it from a power source won’t take a minute.

Leave it to cool down

If your water heater has been operational leading up to the moment you think it needs flushing, you’ll have to leave it to cool down before you proceed. You don’t want to suffer burn injuries for the sake of trying to flush your heater, so the best thing to do after you’ve turned it off is to leave it to cool off.

Put on your heat-resistant gloves

You must be wondering why you’ll need heat-resistant gloves if you’re already willing to wait for the unit to cool off. We believe you shouldn’t leave anything to chance, so we recommend you wear heat-resistant gloves while you flush your water heater.

Work in ventilated space

Ensure the space you’re working in is well-ventilated. You want to avoid inhaling any potentially harmful fumes that might be present in the room, so the best thing to do is to work in an area that has plenty of ventilation.

Always read the manual

There’s a reason every home appliance or device comes with a manual. You can always check the Rheem tankless water heater manual to see how the manufacturer advises you to flush your heater.

Shutting Down Your Tankless Water Heater

This might seem like a simple task or a bit too easy, but if you shut down your Rheem tankless water heater incorrectly, you risk damaging the unit, which will cost you more in the long run. Follow the steps below to shut down your tankless water heater correctly:

Locate the power source

The first thing to do is to locate the power source. Something must connect the unit to the power source, which is what you’re looking for. It is usually at the side of the unit.

Flip the switch

Once you’ve located the power source, the next thing is to shut off the unit. You can do this by flipping the power switch or completely unplugging the unit from the power source.

Close the valves

Find the valves that regulate hot and cold water (the valves are usually labeled). Turn each one clockwise to close it.

The Flushing Process

Now, the moment we’ve been waiting for – the flushing process. We already know the safety precautions we must take and also how to shut down the unit. Now, let’s move on to the flushing process. Follow the steps below to get things right:

Prepare the bucket

Remember the 5-gallon bucket we talked about earlier? Now is the time to put it to use. Pour your white vinegar into the bucket (it should be enough for the pump to submerge).

Connect the hoses

Connect the garden hoses to both ends of the water heater. The connection must be very secure to avoid leaks.

Start the pump

Once the hoses have been connected securely, place the pump in the bucket filled with vinegar and let it run into the unit. Let the vinegar solution sit in the unit for about 1 hour to remove the mineral deposits in it. Don’t try to rush the process. You can go do something else while you wait.

Disconnect the hoses

After an hour, place a bucket under the discharge pipe while disconnecting the hoses to let the vinegar solution and whatever dirt it has accrued run out easily. Carefully disconnect whatever connections you have to the inlet and prepare to get the water heater running again.

Worth Reading: A Simple Step by Step Guide to Flushing Your Tankless Water Heater

Restarting Your Tankless Water Heater

Now that the flushing process is all wrapped up, it’s time to restart your tankless water heater and get it running. Firstly, you have to reopen the hot and cold water valves to let the water flow back seamlessly. Make sure the connections are secure. Once that is done, turn on the unit by plugging back its cord into the power source and flipping the switch. Afterward, you can let water flow through the unit and run hot water through your nearest faucet. If everything goes well, it means the whole process is a success!


In conclusion, by following this comprehensive guide to flushing your Rheem tankless water heater, you can effectively maintain your unit’s performance and extend its lifespan. Regular maintenance ensures a consistent hot water supply and optimal efficiency. Flushing your water heater is a great way to extend its lifespan and keep it running smoothly. Remember, prioritize safety and follow our detailed guide carefully, and you’ll have no problem maintaining your tankless water heater.

Frequently Asked Questions

Can I use a commercial descaling solution instead of white vinegar?

Absolutely! However, ensure this commercial descaling solution is designed specifically for tankless water heaters. We recommend using a descaling solution that does not contain harmful chemicals.

Is it safe to flush my water heater even if I haven’t done it before?

You have to start somewhere, right? It is completely safe if you follow our step-by-step guide and prioritize safety.

Do I need a professional to flush my tankless water heater?

You won’t need to hire a professional if you can follow our step-by-step guide.

How often should I flush my water heater?

You should always try to flush your water heater every 6 months, especially in an area with hard water.

Can I use any type of hose for the flushing process?

Garden hoses are fine for flushing tankless water because they’re readily available and durable.