
Want to learn how to properly flush a water heater?
Over time, sediment buildup at the bottom of the tank reduces efficiency and increases the chances of leaks or failure.
In this guide, we’ll go over…
- How to flush a water heater
- Signs that it needs flushing
- Common drainage problems when flushing
- And more…
Let’s get started!
Power Flush Method (Most Popular)
The power flush method is the most popular method to drain a water heater of sediment.
It involves emptying the water heater and then rapidly opening and closing the cold water valve above the unit.
The rapid flow of cold water creates turbulence and stirs up stubborn sediment at the bottom of the tank. The sediment is drained out, and then the process is repeated until the water runs clear.
The main advantage with this strategy is that more sediment is stirred up and removed, rather than just draining it by gravity alone.
A disadvantage is that due to the pressure of spraying water inside the tank, there is an increased risk in older water heaters of causing a leak if it has never been flushed before.
Gravity Method (Older Water Heaters)
If you’re concerned about damaging a water heater that is 5 years or older and has never been flushed, you can do a simple gravity flush.
Older water heaters sometimes have sediment that clogs microscopic cracks in the tank, preventing leaks. This is why flushing an old water heater can sometimes cause a leak.
So if your water heater is 5+ years old, you are unsure about past maintenance, notice rust around the tank — go with a gravity flush or don’t do any flushing at all.
Gravity flushing means you drain the tank without the additional step of agitating the bottom of the tank by rapidly opening/closing the cold water supply. You likely won’t remove as much sediment but it’s gentler on the tank if you are concerned with leaking.
Determine Age
Homeowners can determine the age of their water heater by looking at the data sticker on the tank. Sometimes the year is printed directly on it but others you’ll need to look up the serial number. The year of manufacture (last two digits) is typically encoded in the first 4 numbers of the serial number — either the first two numbers or the last two.
Tools And Supplies Needed
- Garden Hose: A hose will be needed to connect to the drain valve and long enough to reach the street, a floor drain, utility sink, or bucket. The shorter the hose, the better it will drain.
- Adjustable Wrench or Flathead Screwdriver: Depending on the type of drain valve, you’ll need a tool to open and close the valve. Some drain valves can be turned by hand, but most require a 1/4 turn with a flathead screwdriver.
- Plastic Bucket: A bucket or storage bin can be useful to gauge the clarity of the water that’s getting drained. I recommend using a clear bucket or bin to more easily see the water clarity.
- Gloves (Optional): Rubber gloves can help prevent scalding when dealing with hot water especially when opening/closing drain valve or TPR valve.
- Wet/Dry Vacuum (Optional): If you have a wet/dry vacuum, it can be a useful tool to clear a clogged drain valve of sediment that’s inhibiting water flow.
- Drain Valve Cover (Optional): If you have a drain valve cover, it can come in handy if the valve leaks when you shut it off. These covers are threaded and cost just a few bucks.
11 Steps To Drain A Water Heater
1. Turn Off Power
It’s essential to turn off the water heater prior to draining it.
If the water heater is allowed to fire up when dry, the heating elements or burner could ignite, potentially damaging the system.
For electric water heaters, simply turn off the breaker at the electrical panel.
If you have a gas unit, turn the thermostat to pilot, vacation mode, or Off completely. Setting the gas thermostat to pilot or vacation mode will prevent the unit from turning on but you won’t have to relight the pilot light when you are done.
Let Water Heater Cool Down
If you want an extra safety layer, you can wait a couple hours for the water heater to cool down to minimize scalding risk.
Open up a nearby faucet on the hot side to help the unit cool down faster.
2. Shutoff The Cold Water Supply Valve
The incoming cold water supply will have to be shutoff in order to get a complete drain.
There should be two valves above your water heater, one for hot water (outgoing) and one for cold water (incoming). Locate and turn the cold water valve perpendicular to the pipe to shut it off if you have a ball valve or straight handle.
A gate valve has a circular handle and it should be turned clockwise to shutoff the flow. Be slow and careful with circular gate valves because they tend to be very old and plumbers don’t typically install them anymore.
Sometimes the shutoff handles for the cold and hot water lines are color-coded blue (cold) or red (hot water).
You can also just feel the pipe for cold or warmth but typically the cold water line is on the right side when facing the water heater from the front.
3. Attach Garden Hose To Drain Valve
After turning off the cold water supply, you will need to attach a garden hose to the drain valve at the bottom of the tank.
Your drain valve may have a cover that needs to be removed, just turn it counterclockwise.
Water heater drain valves are threaded so it should be a simple attachment with a garden hose. Turn the hose end clockwise to tighten it.
Place the end of the garden hose into the street, yard, garden, floor drain, or a bucket. The shorter the run of the hose, the better it will drain. The end of the garden hose should always be level with the drain valve or lower.
It’s essential that the hose only has a downward or level slope; otherwise, it won’t drain or will drain very slowly. Homeowners may also need to install a small water pump to the hose, and then a secondary hose to the water pump in order to get the water to drain up a slope or a long distance. A basic hose water pump can be bought online for $45.
Prevent Scalding and Comply with Local Regulations
If draining the tank into the street or garden where kids may be playing, I strongly recommend monitoring the draining to avoid scalding injury.
To be safe, you could also turn off the water heater and just let it cool down. Be aware that your HOA or local code may have restrictions on dumping water into the street.
I invite you to also read our guide on water heater building codes here.
4. Open Bathtub Faucet To Break Air Vacuum
It’s important to open up a nearby faucet on the hot side to help the water heater drain.
A close by bathtub faucet is the best option because it allows the most air into the system.
The water heater has a vacuum, so opening a faucet’s hot water allows air into the system to speed up drainage. It is a similar phenomenon to holding the top of a straw with your finger — the water won’t drain out due to suction.
The increased air will reduce pressure inside the tank and also help minimize damage to components. As the water heater drains, you may hear air get sucked into the faucet with gurgling, hissing, or sputtering sounds.
5. Open Drain Valve
After opening a nearby sink, it’s time to open up the drain valve.
There are different types of drain valves, but the most common is a brass valve with a screw at the top. You will simply need to use a flathead screwdriver and make a 1/4 turn so that it is parallel with the drain valve.
If you have a handle on your valve, turn it parallel to the valve exit. A plastic drain valve will simply need to have the round handle turned counterclockwise with your hand.
I recommend placing a towel underneath the drain valve to catch any water that may spill out when opened.
6. How To Handle Stopped Or Slow Drainage
If the water heater is draining very slowly or won’t fully drain, sediment may be blocking the drain valve. Since the drain valve is at the lowest part of tank, it sometimes gets clogged.
The clues that a water heater isn’t fully draining includes the water flow moving to a trickle, the tank still feels heavy, or if there is a solid thud when you tap the tank.
Likewise, if someone is monitoring the end of the garden hose, you can estimate if the tank has fully drained. If the water heater is drained, move on to step #7 since agitating the bottom of the tank may also clear the clog.
Use A Wet/Dry Vacuum Or Wire
In addition to agitating the bottom, attaching a wet/dry vacuum to the drain valve can help suck out any sediment that is clogging the drainage.
Even something simple like a piece of metal wire from a clothes hanger or the end of a kitchen utensil inserted into the drain valve can help dislodge debris.
I recommend closing both valves at the top of water heater and closing any open faucets to re-create the air vacuum in the tank. Without the air vacuum, when you remove the garden hose, water may spill out onto the floor.
Attach A Water Pump
A great way to ensure strong drainage is to install a simple and cheap hose water pump. The water pump will help the tank drain properly and to a faraway area like a garden or street.
Increase Air Flow To Tank
An air locked water heater will prevent the initial drain but it also may stop the drainage later on.
This basically means that there is a vacuum somewhere in your plumbing system similar to putting your finger on the top of a straw. Without air flow, the water simply won’t drain to the suction force.
To solve this issue, you can open up a 2nd nearby faucet at a sink or tub on the hot side. In addition, you may want to carefully open up the TPR valve to help break the air lock.
Opening TPR Valve
The TPR valve is the temperature-pressure-release valve which has a long plastic pipe attached to it.
These valves are supposed to have extension pipes that terminate just a few inches above the ground in order to know if it ever leaks and to prevent scalding.
It is essential that the the water level is below the level of the TPR valve otherwise scalding water may get blasted onto the floor or possibly yourself.
TPR valves that are leaking, improperly terminated, or missing extension pipes is a common flag during home inspections.
7. Open and Close Cold Water Supply
Once the tank has drained, it’s time to create turbulence in the tank to stir up the sediment at the bottom.
Open the cold water supply at the top of the tank and allow it to spray into the water heater for 10-15 seconds. The cold water supply has a long tube that extends to the bottom.
After agitating the bottom, shutoff the cold water supply and allow the tank to drain again.
I recommend inspecting the drained water to determine how much sediment is getting removed. You may notice cloudy/discolored water or flakes in the water which is why a clear bucket or clear bin is so useful.
Repeat this step until the water comes out clear.
8. Close Drain Valve And Remove Garden Hose
After you are satisfied with the clarity of the water, close the drain valve and remove the hose.
Check for any leaks from the valve and retighten it if necessary. If there is a small leak in the valve after closing it, you can install a drain valve cover.
9. Open Cold Water Supply And Refill Tank
Open up the cold water supply again to fill up the tank.
I recommend keeping the nearby faucet open to help with the refilling and prevent air locks.
It’s essential to completely fill up the tank before powering on the water heater to prevent dry firing. If the water heater tank ignites prior to being full, the burner, heating element, and other components can get damaged.
10. Turn On Power
If you have an electric unit, flip the circuit breaker back on to restore power.
With a gas water heater, turn the thermostat back to your desired temperature.
Please make sure that the entire tank is filled up with water before turning the water heater back on. Carefully inspect the valves above the water heater and the drain valve for any small leaks.
11. Drain Valve Leak
If you have a leaking drain valve, you can install a $5 drain valve cover. These covers are threaded and you simply tighten it on the drain valve.
If a new cover doesn’t fix the leak, you may need to replace the drain valve, jump to the steps here.
Signs A Water Heater Needs Flushing
- Unusual Noises: If you hear popping, rumbling, or banging — your water heater likely needs a thorough flushing. The sounds are caused by steam escaping the layer of sediment, rising in the tank, and causing the entire tank to resonate with noise.
- Utility Cost: If there is a sudden increase in your utility bill (gas or electric), it may be related to the decreased efficiency of the water heater. A whole house electrical monitor or an outlet monitor for the water heater can alert you to the exact cost increase.
- Changes in Water Temperature: If there are unusual changes in temperature (from hot to warm to cold), it can indicate that the water heater is having trouble with heating due to sediment buildup.
- Cloudy Water: One of the last signs of a water heater that needs flushing is cloudy or discolored water. It means that enough sediment is flowing out of your water heater to actually become visible at the sink.
- Low Water Pressure: You may notice reduced water pressure at all or most of your plumbing fixtures. The lower water pressure is a result of tank sediment restricting the water flow of your pipes and fixtures. Don’t forget that faucets usually have screens that may need to be cleaned of sediment.
What Exactly Is ‘Sediment’?
Mineral sediment is the main target of water heater flushing and it is a result of hard or mineral-rich water.
The majority of sediment is from dissolved minerals in the water that solidify and sink to the bottom of the tank. This physical process is very similar to how sedimentary or fossil-rich rocks are formed in nature.
The other types of sediment you may find in your water heater is iron flakes, sand, dirt, or organic debris especially if you live in a rural area or on well water. The two most common minerals that need to be flushed are calcium and magnesium.
If you hear popping or rumbling from your water heater, it is likely from steam bubbles traveling through the sunken sediment at the bottom.
The Problem With Sediment
The big problem with accumulated sediment is that the minerals can cover the electric heating element (typically lower one) or create a barrier above the gas burner. In essence, it requires more energy to heat the water than if there wasn’t sediment blocking the heat transfer.
It also means you’ll get less hot water since it takes longer to heat up and there is less volume/space for hot water.
Water heater lifespan is mostly related to the amount of minerals in your water. The sediment disrupts the efficiency and begins to erode the glass or enamel lining and exposes the steel tank to corrosion.
Scheduled Maintenance
Unfortunately, the vast majority of homeowners never maintain their water heaters. A regularly maintained water heater can extend the life up to 20 or even 30-years.
The average lifespan of a water heater is typically in the 10-12 year range when maintenance is neglected and the tank starts to leak. Once the tank leaks, there is no way to repair it and replacement is needed.
You may also want to consider the pros and cons of tankless water heaters instead of traditional.
- Soft Water: If you have a water softening system or have naturally have soft (low mineral content) water, you can probably get away with only flushing the tank every 2-3 years. I invite you to see our guide on how water softener systems work.
- Hard Water: If you have hard water, flushing the tank at least once a year or even bi-annually may be needed.
A simple home water test can determine the extend of your water hardness and maintenance requirements.
You may also want to consider installing a whole house water softening system if you have hard water which will reduce the flushing requirements. If you have debris sediment like iron, sand, or dirt — a whole house sediment filter should do the trick.
Anode Rod Replacement
In addition to flushing, regularly replacing the anode rod is essential to maintenance.
The anode rod, also called a sacrificial rod, is a metal rod that sits inside the tank. The main idea is that the anode rod corrodes instead of the steel tank. Anode rods also create ions in the water that helps prevent rust and corrosion to the tank lining.
Most anode rods will need replacing every 3-5 years, but with hard water — it may need to be replaced sooner.
To remove and inspect the anode rod, you will need an adjustable wrench. The top of the anode rod will be accessible at the top of the water heater. Turn the large nut counterclockwise to loosen and pull out the rod.
A newer water heater may have a different procedure for installation, check out the manual for your specific model.
Anode Rod Leak Risk
Be careful with a water heater that has never had the anode rod replaced or inspected because the threads may be seized. If the threads are seized, and you use force to loosen it, the threads may get damaged and cause a leak.
If you have an old water heater (5+ years old) where the anode rod has never been replaced, I recommend leaving it alone and only flushing the tank.
6 Steps To Replace A Drain Valve
If you have a leaking drain valve, an old plastic drain valve, or just feel the need to install a new one, installing a new 3/4″ brass drain valve isn’t too difficult. A new water heater drain valve can be purchased online for as little as $20 to $30.
I recommend buying a full port brass valve that has a 3/4-inch diameter. These high quality and larger drain valves will drain better with less chances of getting clogged.
It’s essential to make sure that the length or ‘shank length’ of the new valve is the same length as your old one. If the valve is too short, you won’t be able to reach the threads and screw it in. In addition, you want to make sure that the shutoff handle has enough space to be fully opened and closed.
- The first step is to turn off the water heater and make sure there is an air vacuum. Turn off all valves and faucets to ensure there is a vacuum so water doesn’t drain when you pull out the old valve and you do NOT have to drain the tank.
- Turn the water heater OFF. You also may want to let the water in the tank cool.
- Make sure to have the new drain valve is ready to quickly install once you pull out the old one. Wrap the threads of the new drain valve with Teflon tape and have it ready to go.
- Place a towel underneath the valve to catch any water that comes out. It should be just a little water if there is an air vacuum.
- Use an adjustable wrench to turn the old drain valve nut counterclockwise.
- Once the old valve comes out, quickly insert the new drain valve into the hole and tighten the threads clockwise. Tighten the new drain valve with the wrench.
Final Thoughts
Water heater flushing is one of the little-known aspects of home maintenance that many homeowners don’t know about. The two main flushing strategies are the power flush and gravity method.
The power flush method involves quickly opening and closing the cold water valve after draining to agitate sediment.
If you have an old water heater or are concerned about damaging components, a simple flush with gravity is all you need.
A regularly flushed water heater improves the efficiency, speed, noise, hot water quantity, and longevity of your water heater. Properly flushed water heaters will also help reduce the likelihood of leaks which is the death knell of water heaters — at which time it will just need to be replaced.
I hope you enjoyed this article! Ask me a question below or share your experience with water heater maintenance.