If you're heading south for the winter or leaving a vacation home empty, it's a good idea to winterize hot water heater tanks to avoid a messy, expensive disaster. There is nothing quite as heartbreaking as walking into a basement or a utility closet in the spring only to find that your heater turned into a giant, cracked ice cube over the New Year. It happens more often than you'd think, but the good news is that preventing it is pretty straightforward and doesn't require a degree in plumbing.
Why you shouldn't skip this chore
When water freezes, it expands by about nine percent. That might not sound like a huge deal, but inside a rigid steel tank or thin copper pipes, that expansion exerts massive pressure. If that water has nowhere to go, it's going to make its own space by splitting the metal wide open.
Beyond the risk of the tank itself cracking, there's the issue of the pipes connected to it. Even if the heater is in a semi-insulated garage, a sustained cold snap can turn the standing water inside those lines into solid ice. If you aren't around to catch a leak once things thaw out, you're looking at significant water damage to your floors, walls, and potentially your foundation. Taking an hour to drain the system is a much better use of your time than dealing with insurance adjusters later.
Getting started: Safety first
Before you even touch a wrench or a garden hose, you have to cut the power or fuel source. This is the part people usually forget, and it's the most expensive mistake you can make.
If you have an electric water heater, go to your breaker box and flip the switch to "Off." If you drain an electric tank while the power is still on, the heating elements will burn out in a matter of seconds because they aren't submerged in water. Replacing those is a pain you don't need.
For a gas water heater, you have two options. You can turn the dial to the "Pilot" setting if you're just keeping the house at a low temperature, but if you're fully winterizing and shutting everything down, just turn the gas supply valve to the "Off" position.
The step-by-step drainage process
Once the power is off, it's time to get the water out. You'll need a standard garden hose and a place for the water to go—either a floor drain or out a nearby door or window.
- Shut off the water supply: There should be a cold water inlet pipe leading into the top of the heater with a shut-off valve. Turn that handle until it's closed. This stops new water from rushing in while you're trying to empty the tank.
- Hook up the hose: At the bottom of your water heater, there's a small drain valve that looks like a outdoor spigot. Attach your garden hose to this. Make sure the other end of the hose is somewhere that can handle a few dozen gallons of water.
- Open the drain valve: Turn the handle or use a flathead screwdriver (depending on the model) to open the valve.
- Break the vacuum: You might notice the water only trickles out at first. This is because of the vacuum effect. To get the water flowing freely, go to a sink somewhere in the house and turn on the hot water tap. This lets air into the system, allowing the water to dump out of the bottom of the heater much faster.
While the tank is draining, it's a good time to keep an eye on the color of the water. If it looks "chunky" or cloudy, that's just sediment—calcium and minerals that settle at the bottom over time. Draining the tank actually doubles as a great maintenance task because it flushes that junk out, which helps your heater run more efficiently when you turn it back on.
Don't forget the pressure relief valve
Every water heater has a T&P (Temperature and Pressure) relief valve, usually located near the top or on the side with a small lever. While the tank is draining, flip that lever up. This helps ensure that every last drop of water can exit the system. Just be careful, because if the water is still hot, it could splash. It's usually best to let the water cool down for a few hours after turning the power off before you start the actual draining process.
What about tankless water heaters?
If you have a tankless system, you might think you're off the hook because there isn't a giant vat of water sitting in your house. Unfortunately, that's not quite how it works. Tankless units have a heat exchanger—a series of small, narrow copper pipes—that are extremely sensitive to freezing.
To winterize hot water heater units of the tankless variety, you usually need to use an air compressor to blow out the remaining water from the internal lines. Many modern tankless units also have small drain plugs at the bottom. Check your specific manual, but the general rule is: if there's a drop of water left in those tiny copper fins, it can cause the unit to burst.
Dealing with the "leftovers" in the pipes
Draining the heater is the big job, but don't forget the rest of the plumbing. Once the heater is empty, you should blow out the hot water lines throughout the house. If you leave water sitting in the pipes that lead from the heater to your shower or kitchen sink, those can still freeze and crack.
A lot of people like to use a bit of non-toxic RV antifreeze in their drain traps (the U-shaped pipes under the sink), but never put antifreeze inside your actual water heater. It's nearly impossible to flush out completely, and you definitely don't want to be bathing in or cooking with that stuff come springtime.
Bringing the system back to life
When the snow melts and you're ready to move back in, you can't just flip the power back on and call it a day. There is a specific order to doing things so you don't ruin your equipment.
First, close the drain valve at the bottom of the heater and remove the hose. Open the cold water supply valve to start filling the tank. Go back to that hot water tap you opened earlier and keep it running. At first, you'll hear a lot of hissing and sputtering—that's just the air being pushed out of the lines. Once a steady stream of water is coming out of the faucet, you know the tank is full.
Only then should you turn the electricity back on or relight the gas pilot. If you turn the power on before the tank is 100% full, you will fry your heating elements, and you'll be starting your spring with a repair bill instead of a hot shower.
Final thoughts for peace of mind
Winterizing isn't exactly the most exciting way to spend a Saturday morning, but it's one of those "ounce of prevention" things that pays off massively. If you're in a climate where the ground freezes, taking the time to winterize hot water heater components is just part of being a responsible homeowner.
It takes maybe thirty minutes of actual work and an hour of waiting for the water to drain. Compared to the thousands of dollars you'd spend on a new heater and a restoration crew to dry out your basement, it's a pretty solid trade-off. Plus, you'll sleep a whole lot better knowing your pipes aren't under pressure while you're away.