Knowing How Often to Flush a Water Heater Can Save You Thousands

Why Does Flushing Your Water Heater Matter?

Flushing and draining your water heater is all about removing sediment and minerals from the system. The buildup of sediment causes scaling and corrosion over time — even in tankless water heaters. 

Homeowners that don't regularly flush their water heaters experience 3 major issues:

Reduced water heater efficiency. Scaling near your heating element or heat pump reduces its ability to heat up your water. This decrease in efficiency means it requires more energy to properly heat your water. 

Corrosion in your plumbing system and pipes. Simply put: water plus minerals equals corroded metal. The sediments and minerals in your drinking water supply — especially if you have hard water — will corrode your plumbing system without proper flushing.

Potential water damage in your home. Over time, corrosion and scaling in your tank, pipes and valves causes erosion and leaks throughout your plumbing system. These leaks lead to burst if they aren't immediately addressed. Neglected water heaters eventually lead to flooding in your walls or basement.

A Tankless Water Heater Horror Story

A HOMR member called us with a simple question recently — “How often should I flush my tankless water heater?” Sadly, it turned out they called a few months too late.

The member inherited a tankless water heater when they purchased a new home. They noticed that hot water wasn't coming through quickly enough, and the hot water flow was inconsistent when it arrived. They asked us to help diagnose the issue, and we got them a free quote with a local water heater maintenance pro.

Unbeknownst to our member, the previous owners of the house neglected to flush the tankless heater for several years. When our expert analyzed the issue, the sediment buildup had already caused damage to the heating element and corroded part of the system.

Just like that — bam! A new water heater installation set them back $5,000. 

HOMR exists to prevent these horror stories from happening to you. Our 24/7 home management service ensures your service calls and emergencies are handled quickly and professionally at any time of day.

Of course, the ideal situation involves never having to call us for emergency water heater repair. Learn how to flush your water heater safely and efficiently, and save yourself the cost of calling a repair service or buying a new heater.

How to DIY Flush a Tankless Water Heater

We suggest purchasing a water heater flushing kit to properly DIY flush your tankless water heater. Most quality water heater flushing kits cost between $100-$149.

Use 3-4 gallons of undiluted white vinegar as the cleaning agent for your flushing process. Never use chemicals of any kind when cleaning your water heater.

Follow this simple 7 step guide to flush your tankless water heater.

Step 1: Turn off the lines to your tankless heater.

You should see a blue inlet valve and red outlet valve to your tankless heater — these are your cold water supply valve and hot water supply valve. Turn them off.  Turn the gas valve off as well.
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Step 2: Connect hoses to your tankless water heater valves.

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‍Connect hoses to your cold and hot water valves. A water machine hose is preferable to a garden hose for tankless systems. 

Step 3: Connect water heater flushing kit's circulation pump.

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Attach one end of the kit's inlet hose to the circulation pump, and place it in a large bucket — make sure the bucket holds at least 5 gallons of liquid. Attach the other end of that hose to the discharge side of the pump. Place the outlet hose in the bucket.

Step 4: Add 3-4 gallons of undiluted white vinegar.

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‍ Pour the undiluted white vinegar in your bucket, and add one gallon of water. 

Step 5: Drain and flush your water heater.

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Open your water valves and start the circulation pump. Refer to specific instructions in your water heater flushing kit for exact details of this process. The vinegar cleaning agent will remove magnesium, calcium and other sediment from the heater.

Step 6: Clean and flush the system.

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‍After 90 minutes to 2 hours, turn off the circulation pump. Turn off both water valves, and disconnect the cold water inlet hose. Leave the hot water outlet hose connected, and turn the cold water valve on. Let the water flush through the outlet hose for 10 minutes, then turn off your cold water valve.

Step 7: Reconnect the lines and turn on your valves.

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‍Disconnect the water heater flushing kit and circulation pump. Reset all original components of your tankless water heater to the way they began. Turn on your water valves first, then your gas valve.

How Much Does it Cost To DIY Flush a Tankless Water Heater?

Flushing your own tankless heater costs $60 or less with the proper equipment.

Perks of Hiring a Pro to Flush Your Water Heater

It’s tempting to attempt to flush your own home water heater, especially when the cost is so low. But if you're not a particularly handy person — ideally one with some HVAC knowledge — it’s better to hire a professional water heater expert for the job.

From safety to quality, here are 6 perks of hiring a pro to flush and drain your water heater:

1. The Right Tools. Your water heater expert already has the requisite tools to drain, flush and clean your water heater — and they’re far better than the $100 kit you’ll buy at a big box hardware store.
2. No Burn Risks. Do you really feel comfortable working around boiling water that can spray out of a poorly connected hose? Hiring a pro keeps you far away from the risk of burns and other injuries.
3. Increased Heater Lifespan. Expert water heater drainage and flushing erases the sediment and scaling from your system. Studies show this increases the lifespan of your hot water heater by over 5 years. 
4. Repair Prevention. A professional notices warning signs and potential issues in your water heater long before you will. 
5. Warranty Coverage. Hire a water heater expert or plumbing contractor that offers a workmanship warranty on their labor — if any short-term problems arise, they’ll be covered.
6. Reasonable Cost. The cost to hire a pro to flush your water heater is less than $50 more than the cost of buying a kit and doing it yourself.

How Much Do Contractors Charge to Flush a Tankless Water Heater?

It costs $200-250 to have your tankless water heater flushed by a professional.

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How to Flush a Standard Water Heater

Follow this easy 9 step guide to flush your standard water heater tank.

1. Turn your tank water heater thermostat off. An electric water heater thermostat is controlled by your breaker box — throw the corresponding switch. A gas water heater thermostat is usually near the bottom of your tank.
2. Turn off gas (if necessary) and water lines to your tank. If you have a gas heater, turn the valve on your gas pipe to “off”. Turn your cold water valve to the “off” position for all types of water heater tanks.
3. Turn on a hot water faucet in your tub. Let one hot water faucet run inside your home as your flush your tank. This prevents a vacuum from forming in your pipes.
4. Connect a garden hose to your spigot/drain valve. Ensure the garden hose leads outdoors, ideally a good distance away from your home's foundation.
5. Drain your tank. Open the spigot/drain valve. Drain your tank until you no longer see sediment or rust colored water coming out of the hose. If you haven't flushed your system in a few years, the water may not run clear until your tank is fully empty.
6. Flush your tank. Turn the cold water valve to your tank back on. You may see rust colored water again for several minutes — that's normal. Run the water until it is clear again.
7. Close the spigot, turn off your cold water valve, reconnect your lines, and turn off your tub faucet. 
8. Gas water heaters: Turn on your gas and water lines to your tank. 
9. Electric water heaters: Throw your breaker switch back on. You will need to relight your electric water heater's pilot light. Turn your water lines back on.

How Much Does it Cost to Flush a Water Heater?

It costs $150-200 to have your standard water heater flushed by a professional. Flushing your own water heater costs $60 or less with the proper equipment.

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Rather let the pros flush your water heater tank? Get a free quote now.

Answers to Your Top Water Heater Flush Questions

Over 1,200 Americans type “How often should I flush my water heater?” into Google each month. Here are the answers to 4 of the most-searched related questions about flushing your water heater system.

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How do I know if my water heater needs to be flushed?

As a rule, a tankless water heater should be flushed once per year. A standard water heater should be flushed at least once every 2 years. However, there are several instances where your water heater should be flushed more often.

If you have hard water, flush your water heater tank every 6-9 months. This alleviates sediment buildup, which can cause corrosion in your tank. Corrosion leads to water tank damage and unwanted minerals entering your home's water flow.

If you notice rust colored water, or you aren't getting consistent hot water, it's time to flush your water heater.

Can I flush my water heater myself?

Yes, you can flush a hot water heater yourself with the proper safety precautions. The water inside your tank is scalding hot — even hotter than what comes out of your hot water tap.

Let the water inside your heater cool before draining, or consistently add a cold water supply as you flush the system. Avoid contact with the drain valve — wear thick gloves when attaching a garden hose. 

Stand clear of the water as it drains, and do not touch the hose with your bare hands as the hot water passes through.

How long does it take to flush a hot water heater?

The amount of time it takes to flush a hot water heater depends on 4 factors:

• It takes roughly 60-90 minutes to fully flush most water heater tanks.
• Tankless water heaters and larger tanks may take up to 2 hours to flush and drain completely.
• These times reflect using undiluted white vinegar as your cleaning agent — it’s faster to use a chemical cleaning agent, but we don’t suggest putting those anywhere near your water supply.
• Homeowners who conduct regular flushing will find the process takes slightly less time to complete.

When is the best time to flush a water heater?

Water heater maintenance experts suggest fall as the ideal season to flush a hot water heater. Fall maintenance ensures your hot water heater is ready to provide a consistent hot water supply during the cold winter months. 

The type of water heater you own doesn’t affect this advice. Accumulated sediments and minerals interfere with your hot water tank heater, even in electric hot water heaters.