10 Mistakes To Avoid When Maintaining Your Water Heater

The water heater sits in the basement or the closet and quietly does its job for years. Then one morning the shower runs cold, and suddenly it is the most important appliance in the house.

An unfinished basement with exposed joists, support poles and stairs.

This Old House, in a guide by Lance Marques first published in 2010 and updated April 20, 2026, lays out how to maintain a water heater and the warnings that go with it. Here are 10 mistakes to avoid, drawn from that guide.

Water heaters hold hot water under pressure, and some burn gas or oil, so a careless move can do real harm. Read each item with that in mind, and when the guide says to call a licensed professional, believe it.

Your own heater’s manual comes first. Keep it handy, because the manufacturer’s instructions can differ from general advice.

1. Waiting For A Problem Before You Maintain It

This Old House notes that many people only replace a heater during an emergency, when “they only have 24 hours to get it changed.” That is a stressful way to shop.

Regular upkeep is the better path. The guide suggests checking for leaks, tightening connections and keeping the area around the heater clean and free of dust and debris.

2. Skipping The Power And Water Shutoff

Before any work starts, the guide says to turn off the breaker for an electric heater, or set the gas valve to pilot for a gas one. Then close the cold water supply valve on the inlet line.

It also says to wait several hours for the tank water to cool, and to wear gloves and goggles. For gas units, ventilate the area.

3. Forcing A Temperature And Pressure Valve

The TPR valve is a safety part. This Old House warns that forcing one that will not reseal, or is malfunctioning, can create dangerous pressure in the tank.

The guide adds that mineral buildup can keep an older valve from resealing, so testing it can cause a leak that was not there before. Only test it if the manufacturer allows manual testing.

4. Capping Or Blocking A Dripping Valve

A drip from the TPR discharge pipe is annoying, so some people plug it. This Old House says not to cap or block a persistent drip, because it indicates the valve needs repair.

Treat the drip as a message. Call a licensed professional to look at it.

5. Forcing A Stuck Anode Rod Or Drain Valve

The anode rod protects the tank from rust, and the guide says to replace it if it is less than half an inch thick or coated with calcium. But it also says not to force a stuck rod, or a clogged, hard-to-open or corroded drain valve.

Doing so can cause leaks or prevent the valve from resealing. If something will not budge, stop and bring in a pro.

6. Ignoring Noises, Rusty Water And Odd Smells

This Old House lists several warning signs. Popping or rumbling usually means sediment buildup, and the guide says to flush the tank and consult a professional if the noise continues.

Rusty water may point to internal corrosion or a failing anode rod, and a sulfur smell may indicate bacteria. Heavy sediment can worsen after a full flush, so the guide says to have the system evaluated rather than pushing through.

7. Insulating Over The Controls, Labels Or Valve

A tank blanket can help, and the guide says to check the manufacturer’s guidance first. But keep insulation off warning labels, the thermostat and the TPR valve.

Cut the blanket around pipes and controls so everything stays visible and working.

8. Covering The Top Of A Gas Or Oil Heater

This is a firm rule in the guide: never cover the top of gas or oil water heaters with insulation. The top is where the heater vents.

If you are unsure how to insulate yours, skip it and ask a professional.

9. Using Foam Pipe Insulation Near A Gas Flue

Foam pipe wrap is cheap and easy, which makes it tempting. This Old House warns that foam near a gas flue is a fire hazard, and says to use heat-resistant fiberglass wrap instead.

Keep the right material in the right place and your pipes stay protected.

10. Doing Gas Or Valve Work Yourself

The guide is clear that work involving gas lines, heating elements or the TPR valve is best left to a licensed professional. It also recommends annual professional inspections, especially for gas heaters.

That visit is cheap compared with the cost of a repair gone wrong. Please do not gamble on gas.

One more tip from the guide: set the temperature dial to 120 degrees F. The guide says each 10 degree reduction can save up to 5% on energy costs.

And if your heater is more than 10 to 15 years old, costs more than half the price of a new installation to repair, or keeps running out of hot water despite maintenance, the guide says it may be time to replace it.

Your homework this week is simple. Find the date on your tank, look for drips or rust, and book a professional inspection if it has been a while.

Willow and Hearth