The enemy of all steel tank water heaters is rust. Eventually all of them develop a leak somewhere.
1) Flush the water heater
Debris collects at the bottom of your water heater. Impurities in the water, rust from the tank walls, and particles carried in from the piping system all settle at the bottom.
If left in heater for years, this debris can cause your heater to fail prematurely. To ensure your heater reaches it's maximum service life, you have to flush the debris from the water heater once a year.
Connect a hose to the outlet at the bottom of your heater. Place the other end of the hose near a drain either inside your home, or outside. Open the drain valve and let 5-10 gallons of water drain from the tank.
Since the water drains from the bottom of the tank, any debris in the tank will be flushed out very rapidly. Close the drain valve.
2) Replace the sacrificial anode
To guard against rust water heaters are equipped with sacrificial anodes. An anode is a long rod made from a material that is less noble (a term from chemistry) than the steel the tank walls are made from. The anode is submerged inside the tank.
Less-noble metal corrodes more easily than noble materials. This means the anode is consumed more rapidly than the tank walls. Hence the name sacrificial anode. Instead of preventing rust, corrosion takes place on the anode. You can read about how this exactly works here: https://en.wikipedia.org/wiki/Sacrificial_anode
Anodes are used up over time. When they are used up the walls of the tank begin to rust. To prevent this from happening it is best to replace anodes every 3 years or whenever the manufacturer recommends. The exact rate at which an anode is consumed depends on many factors. It's impossible to predict the exact point in time an anode should be changed.
The good news is that anodes are cheap parts and replacing them is a simple DIY job. On most water heaters the top of the anode is visible on top of the heater. It looks like a large hex head bolt. To replace it follow the following steps.
- Turn the water off
- Open the lowest tap in your house. This will depressurize the system. If the tap is higher than the top of your water heater you will have to drain little bit of water from the heater to prevent water gushing from the anode's opening.
- Remove the anode. It is screwed into the heater. Simply reverse it out. Penetrating oil can help with arusted bolt.
- Install a new anode. Wrap some plumber's tape around the threads of the anode and screw it into place.
Water heaters with regularly maintained anodes can last decades. Commercial systems have multiple anodes to expend their life.
- Flush your tank yearly
- Replace the anode every 3 years
Eventually, however, every water heater is going to rust out. It's not uncommon for anode replacements to extend a water heater's life well beyond double it's warranty life.