Written by: Corey P.
Plumbing Contractor
November 26, 2023
The national average cost for water heater replacement is $1,700. Stack that up against the average cost of a water heater at about $650 to $700 (most common type), and it can appear that plumbers are charging you a premium for their services. But anyone who has ever had the pleasure of diving into a project with little to no experience knows, you often come out the other side with extra parts, tools, and respect for those who do it professionally.
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With that being said, it is possible for you to change out your water heater yourself. Here we will give you the basic steps to replacing your water heater, what to watch for, and how to be successful.
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Keep in mind that there are significant safety considerations involved with a water heater and most professional installers will know what is safe and what is not.
Average Water Heater Replacement Cost
40-gallon tank (gas)
50-gallon tank (gas)
75-gallon tank (gas)
Tankless (gas)
40-gallon tank (electric)
50-gallon tank (electric)
75-gallon tank (electric)
Tankless (electric)
Type
Cost (USD)
1500
1650
2200
2000
1300
1500
1850
1600
NATIONAL AVERAGE
$1,700
​Step-by-Step
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Step One: Planning​​​​
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As a wise old man once said, "If you fail to plan, then you're planning to fail." This may not be a natural law, but it does feel that way sometimes when we only become reactionary and not proactive in our own success.
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Make sure to gather all tools, parts, and accessories you are going to need. All installations are different and will require different things to overcome different obstacles along the way. Try to go through every single step in the process when making a list before you go to the store. Also, check your shut-off valves for proper working order before beginning.
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Step Two: Draining the Old Water Heater
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First thing we need to do here is shut off the water, electricity, and/or gas. If you're having trouble with the valve located at the water heater, you may have to use the main valve and shut down all the water to your home. If by some chance, you don't have a main valve or don't know where it's located, you're going to have to go to the meter and shut it down there (if you're on a well, just flip the breaker for your pump).
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Now that the water is shut down, we can hook up the hose to the drain valve on the water heater. Making sure the hose is running to a drain or bucket (which will need emptied often), you can crack open the valve and start the draining process. Here's the first major hurdle, if your water heater has a significant amount of sediment built up, draining may be very slow. Remember to open the relief valve to let air inside the tank replace the water as it comes out, or you'll create a vacuum that doesn't allow for the water to move at all. Alternatively, you can open a faucet to achieve the same effect.
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If you have access to a transfer pump, it can reduce the time for draining down to minutes if the water is flowing well. One last note, if the water seems to barely be flowing, ensure you have allowed air to break the vacuum. Then, you can completely remove the relief valve at the side or top of the unit by unthreading it from the tank. This will allow you to pump or siphon water from that point instead of the drain valve.
Make Sure to Turn Off...
Electricity
Natural Gas or Propane
Water
​Step Three: Removing the Old Water Heater
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If the water heater is empty, we can begin the process of removing it from it's home. We start with the gas, propane, or electrical connections and disconnect them. Remember, these should already be turned off prior to draining to prevent the water heater from trying to heat.
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Electric: A non-contact voltage tester is a must have for anyone that is dealing with an electric water heater. Breakers can be mislabeled, I've seen it, more than once. If you are sure the power is off to your water heater, you can begin by disconnecting the wires at the top of the unit. Once disconnected, move them out of the way so you don't have to work around them.
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Gas/Propane: Assuming you're doing well so far, we can move on to the venting for gas and propane heaters. Most heaters are atmospheric vent, meaning the exhaust naturally rises up and out of your home through the vent. The by-products of the fire burning are lighter than air and escape through the roof. There should just be a few screws holding the venting in place. Once the screws are removed, you should be able to remove the section of exhaust pipe immediately attached to the top of the water heater.
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Most gas and propane units nowadays will have a flexible gas connection that can be removed easily with a wrench, but not always. If your unit is "hard-piped," you will need pipe wrenches to disconnect the gas. There "should" be a union, emphasis on should, somewhere near the gas valve allowing you to break open the connection.
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Water Lines: The final step is to disconnect the water lines from the water heater. This can be achieved through a multitude of different ways depending on the last installation method. Some units have flexible connections with threaded ends, others may have di-electric unions, and some will have no other option other than to cut the water lines.
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Now the unit should be completely empty of water and fully disconnected from the water, gas, propane, venting or electrical connections. Using a dolly, or sheer man-power, move the water heater out of the way.
Cut Along the Dotted Line Only
Fragile
New
Water
Heater
Step Four:​ Installing the New Water Heater
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Your new water heater will come in a large box. At the bottom of the box is a dotted line that indicates where to cut to prevent any damage from befalling your new water heater. Standard 30, 40, or 50 gallon tanks will have 3/4 inch threaded nipples factory installed on the top of the unit.
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If your water heater is located in a tight space, you will prefer installing any fittings or connections that you can, prior to putting it into its final resting place. Also, don't forget to put a water heater pan under it if installing in a finished location. This will direct any water that may leak to a drain location of your choosing. If there is no drain nearby, you can cap off the drain and put a water detecting unit that audibly alarms you of water. This is also the step where you confirm your water heater is level.
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Now that it is in place, we can reverse the process of taking out the old with the new. I will refrain from giving you all the different ways of attaching water lines, since there are a multitude of different options depending on the types of water lines in your home. However, if you have PEX, CPVC, PVC, or braided connections and you have a gas or propane water heater, might I suggest installing copper, brass, or galvanized steel water lines the first 18 inches from the top of the water heater. This is to avoid the heat from the exhaust causing wear over time. How does that happen you ask? Well, the exhaust is hot, obviously. And this heat will cause expansion of the water lines. Then they will cool and contract back to normal size. Over time, this process can wear on the integrity of the water lines, causing them to fail, in dramatic fashion.
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Reattach the venting, gas/propane, and/or electrical connections. But DO NOT turn on any of them. We need to fill the water heater with water first. Once it is filled, you need to ensure all your water lines are leak proof.
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If you have the water heater filled, confirmed no leaks, the power or gas reconnected, venting reattached if applicable, and are ready to fire the new unit, this is the time to make sure you have all your connections finalized completely.
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Step Five:​ Confirming Proper Operation
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On a gas or propane water heater, you will need to ignite the pilot light first. Follow the owner's manual for exact instructions or look at the side of the water heater, many of them have instructions printed right on the side near the gas valve. Remember to actually turn on the gas or propane before attempting to light the pilot light, I speak from experience.
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On an electric water heater, assuming you made the proper connections, and I hope you did (follow the owner's manual), all you should need to do is flip the breaker back on. If you turn the power on prior to filling the entire unit with water, also known as dry firing, the elements will over heat and fail. This WILL void your warranty, so please make sure to avoid doing this.
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While your new water heater is firing up, this is where you begin the process of cleaning up. Make sure you wait until you are positive that all connections are not leaking and your unit is working as intended before cleaning up. Nothing worse than dragging all your tools back out.
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Step Six: Finalizing the Install​
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I suggest writing the installation date somewhere on the front of the unit with a permanent marker. Years from now, this will help you determine the life of the unit, and when it may need flushed or repaired.
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Make sure to capture your unit's model and serial number. You will need this when filling out your warranty information with the manufacturer. Most will allow you to do it right from your smart phone, so make sure to get it done within the set amount of time they give you (~10 days). There is usually a warranty card in with the owner's manual documentation.
Write Down the Model & Serial Numbers for Your Warranty
Model #
Serial #
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The final step is setting the water temperature. Electric water heaters will GENERALLY come preset to 120°F. But it's worth confirming to avoid any potential scalding. Keep in mind, the hotter the water, the harder your unit works to maintain the water at that temperature. If you have small children or vulnerable people in your home, I suggest airing on the side of caution and keep your water at 120°F. This lessens the likelihood of any water related burns.
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Tips from a Professional:
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On electric water heaters, make sure to deenergize the unit when making adjustments to the thermostat setting. This is to prevent electric shock.​
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On gas or propane heaters, flexible connection kits have flared connectors. These connections are designed to seat without the use of sealants, however, if their surface becomes marred, it could prevent a proper seal.
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Be sure to put a drain tube on the pressure relief valve (T & P valve). Run this drain tube to about 6 inches from the water heater pan. Do not run this tube to a drain that will allow for the water to be ignored. If water is coming from your relief valve, there is a problem that needs corrected.
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Thermal expansion tanks are often necessary or required by local regulations. If your plumbing system has a water softener, backflow preventer, pressure reducing valve (PRV), or a meter with backflow protection, you need a thermal expansion tank. If you are unsure whether you should install one, then I suggest you install one. They're relatively cheap in comparison to what they help prevent.
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Make sure to recycle your old water heater is possible. You won't get much money from it, but you can rest easy that it won't end up in a landfill for the next 10,000 years.
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Conclusion
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If you decided to install your own water heater, and you've reached this point, give yourself the ole' coveted POB (pat on the back.) You earned it. Chances are, you saved a couple hundred bucks, but most importantly, you probably learned a thing or two. And that my friend, is money in the bank.​
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If you decided against installing your own water heater, well, I don't blame you for that. Give us a call, we can take it from here.
