A.O. Smith Water Heater Maintenance Guide

Ignore a water heater for too long and it usually tells on itself. Utility bills creep up. Hot water gets less consistent. Rumbling starts. In the worst cases, the tank gives out years earlier than it should. A little routine care goes a long way with an A.O. Smith unit, especially if you stay ahead of sediment and catch small leaks before they turn into bigger trouble. These steps fit most A.O. Smith tank-style gas and electric models, but it still pays to check your owner’s manual for anything specific to your model.

At a Glance

• Difficulty: Intermediate
• Time Required: 45 to 90 minutes
• Frequency: Quarterly visual checks with a full annual service
• Estimated Cost: DIY: $15 to $80 | Pro: $150 to $400

Routine Maintenance Schedule

Safety Warnings

Turn off electrical power at the breaker for electric units or set the gas control to Pilot/Off for gas units, and allow the water to cool before opening drains or access panels.

Hot water, steam, gas leaks, and pressure-release components can cause serious injury; if you smell gas, see active leaking, or find a faulty T&P valve, stop and call a licensed professional immediately.

Step-by-Step DIY Guide

If the tank has not been serviced in a while, take your time. Old drain valves can be stiff, and sediment can make flushing slower than expected.

Step 1: Shut Off Power or Gas and Isolate the Tank

Start by shutting the heater down completely. On electric A.O. Smith models, switch off the dedicated breaker. On gas models, turn the gas control to Pilot or Off, depending on what your manual calls for. Close the cold-water shutoff valve above the tank, hook a garden hose to the drain valve, and route the hose to a floor drain, utility sink, or a safe outdoor spot. Then open a nearby hot-water faucet. That relieves pressure and helps the tank drain without glugging and splashing all over the place.

Step 2: Inspect the Exterior for Leaks and Corrosion

Before you drain anything, give the heater a close look from top to bottom. Check the base, the drain valve, the shutoff valve, the hot and cold connections, and any fittings on top of the tank. Rust streaks, white crusty mineral deposits, damp insulation, or even a small puddle are signs something needs attention. On gas units, look at the draft hood and venting too. Soot, rust flakes, or discoloration there can point to venting or burner issues. If the tank shell itself is leaking, not just a fitting, the heater is usually at the end of its service life.

Step 3: Test the Temperature and Pressure Relief Valve

The T&P valve is a safety device, not just another part to glance at and ignore. Put a bucket under the discharge pipe if needed, then carefully lift the test lever for a second or two. Water should come out freely and stop once the lever snaps back down. If nothing comes out, if the lever feels stuck, or if the valve keeps dripping afterward, treat that as a real problem. A bad relief valve is not something to put off.

Step 4: Flush Sediment from the Tank

Open the drain valve and let the water run through the hose. At first, it may come out cloudy, rusty, or full of grit, especially if the tank has been sitting for a year or two without service. Keep flushing until the water starts to run clear. If flow slows down or sediment seems stubborn, briefly crack open the cold-water supply for a few seconds at a time to stir up the bottom of the tank and push more buildup out. This step matters. Sediment is one of the biggest reasons tank heaters get noisy, lose efficiency, and wear out early.

Step 5: Check and Adjust the Temperature Setting

Once the tank is drained and you have things under control, check the temperature setting. Around 120°F is the sweet spot for most households. It is hot enough for normal use but not so high that you are wasting energy or raising the risk of scalding. On gas models, this is usually just a dial adjustment. On electric models, make sure the power is still off before removing any access panel. Many electric water heaters have upper and lower thermostats, so confirm both are set properly before putting the insulation and covers back in place.

Step 6: Inspect the Anode Rod

This is the step many homeowners skip, and it is one of the most valuable ones. The anode rod is there to corrode so the tank does not. With the tank depressurized and partially drained, locate the rod on top of the heater, usually under a hex-head fitting. Use the correct socket and enough leverage to loosen it. When you pull it out, look for heavy pitting, severe thinning, or a long stretch of exposed steel core. If the rod is spent, replace it with one compatible with your A.O. Smith model. If it will not budge or there is not enough overhead clearance to remove it safely, call a plumber and let them wrestle with it.

Step 7: Refill the Tank and Restore Operation

When everything checks out, close the drain valve, remove the hose, and open the cold-water supply fully. Leave a nearby hot-water faucet open until water flows in a steady stream with no sputtering. That tells you the tank is full and the air is out of the lines. Only then should you restore power to an electric unit. Turning electricity back on before the tank is full can burn out heating elements fast. On gas models, return the control to normal operation or relight the pilot as directed by the manual. Stay nearby through the next heating cycle and look over all fittings one more time for leaks.

When to Call a Pro

• Water is leaking from the tank body, not just a fitting or valve.
• The T&P relief valve will not operate correctly or continues to drip after testing.
• You smell gas, see soot around the burner area, or notice damaged vent piping.
• The breaker trips repeatedly, the unit stops heating, or recovery is unusually slow after maintenance.
• The anode rod cannot be removed safely or the tank has heavy internal corrosion.
• Rust-colored water, rotten-egg odor, or loud rumbling continues after a flush.