There is a tank in the basement, the garage or a closet, and most people have never looked at it until the day it does something. This page is about the looking, not the fixing.
What is on this page: where the shutoffs are, what the parts are called, what to inspect and how often, and the one setting with two named authorities behind it.
What is not on this page: any instruction to operate, test, replace or adjust the temperature and pressure relief valve, anything involving the gas supply or combustion air, anything involving the electrical connection, and anything involving draining the tank. Those are licensed trades' work, and on a gas unit some of it is regulated work rather than a matter of preference. Where a step would cross that line, this page stops at the line and says so in the step rather than in a footer.
The four things to find before anything goes wrong
Do this on a calm afternoon. It takes fifteen minutes and it is the whole of the preparation.
1. The cold water shutoff for the heater. A valve on the cold inlet pipe at the top of the tank. Find it, and check it turns. A valve that has not moved in a decade may not move when you need it, and finding that out now is a plumbing job on your schedule rather than during a leak.
Do not force it. If it will not turn easily, that is a plumber, and it is a good thing to have discovered.
2. The main water shutoff for the house. Because the heater's own valve is not always the one you need, and because a whole-house shutoff answers more emergencies than any other single thing in a home.
3. The energy shutoff. On an electric unit, the breaker in the panel, and label it. On a gas unit, the gas shutoff valve at the appliance, and the control knob position that the manufacturer's label describes.
Knowing where these are is the point. Operating them is something you may be told to do by a utility or a professional, and it is not something this page is instructing you to practice on a working appliance.
4. The manual and the model number. The rating plate is on the side of the tank. Photograph it. Every specific question about your unit is answered by that plate and by the manual, and a professional will ask for both.
The temperature setting, which has two authorities behind it
This is the one recommendation on the page with named sources rather than convention behind it.
The US Department of Energy's guidance for most residential applications is to set the temperature at 120 °F, and the Consumer Product Safety Commission urges lowering water heaters to 120 °F, noting that as well as preventing accidents the reduction conserves energy.
CPSC's scald figures are the reason the number is what it is. Its published guidance states that most adults will suffer third-degree burns from a two-second exposure to 150 °F water, from a six-second exposure to 140 °F water, or from a thirty-second exposure to 130 °F water.
Three things follow from that, and the third is the one people miss.
The difference between 140 °F and 120 °F is not a small comfort adjustment. It is the difference between a six-second exposure and a much longer one for the same injury.
Households with young children, older adults, or anyone with reduced sensation or mobility are the ones the guidance is aimed at, because the exposure time assumption is that a person moves out of the water quickly.
And there is a countervailing consideration this page will not resolve for you. Some guidance addresses microbial growth in stored water at lower temperatures, and how that interacts with the scald guidance depends on the system and on circumstances that are not general. If that is a live concern in your household, it is a question for a plumber or your health department rather than for a website, and this page does not adjudicate it.
How to change the setting, if you decide to: on an electric unit the thermostat is behind a panel and that is not covered here; on a gas unit there is usually a dial on the control valve. Your manual is the instruction that applies. And whatever the dial says, verify with a thermometer at the tap rather than trusting the marking.
What to inspect, and how often
None of this involves operating a valve or opening a panel.
Look at the floor and the base of the tank, every few months. Damp, rust, staining or a puddle is the earliest warning there is. A tank that has begun to leak does not stop.
Look at the pipe from the relief valve. There should be a discharge pipe running from it, and it should be directed as your local code requires. Water discharging from it is a fault and it is a call, not something to cap, plug or ignore. Do not test the valve; do not lift the lever to see what happens. That is explicitly not an owner task on this page.
Look at the connections at the top of the tank for corrosion or drips.
On a gas unit, look at the flue and the area around the burner access for soot, scorching or anything blocking the air supply, and if you see any of it, stop and call. Combustion air and venting are licensed territory and a blocked flue is a carbon monoxide question rather than a maintenance one.
Listen. Rumbling or popping from the tank is commonly attributed to sediment. It is an observation to report rather than a thing to act on, and it leads directly to the next section.
Sediment, hard water and why this page does not tell you to drain the tank
Sediment accumulation is real and hard water accelerates it.
Draining or flushing a tank is a job with several ways to go wrong, including a drain valve that will not reseat afterwards, scalding water, and disturbing a tank that has been holding together around its own deposits. This page does not give you that procedure. Whether it is appropriate for your unit is in your manual, and doing it is a reasonable thing to have a plumber do while they are there for something else.
What is worth doing is finding out whether hard water is your situation at all, because it drives this and several other problems in the house, and the answer is specific to your supply rather than to a national map. How to get it is in signs of hard water in the house, which routes you to your utility's own water quality report or a test kit rather than to a table.
The same mineral behavior is what furs up a kettle, and the honest position on descaling frequency, including why no authority publishes an interval, is in how often to descale a kettle.
Where this stops being yours, stated once
- The temperature and pressure relief valve. Do not test it, lift it, cap it or replace it.
- Anything on the gas side. The supply, the connection, the burner, the flue, combustion air. Licensed gas professional, and in most places regulated work.
- Anything on the electrical side. The connection, the thermostats behind the panels, the elements.
- Draining or flushing the tank, unless your own manual describes it as an owner task and you are confident about the drain valve.
- Anything after water has already appeared. A leaking tank is a replacement conversation and often an urgent one.
- Anything involving an expansion tank, a mixing valve or the system beyond the heater. Plumber.
And one immediate action that is not a repair: if you smell gas anywhere near the appliance, leave the building without touching a switch or a phone and call from outside. That response is set out in full, with no troubleshooting step in it, on its own page in this cluster.
FAQ
What temperature should my water heater be set to? The US Department of Energy's guidance for most residential applications is 120 °F, and CPSC urges lowering water heaters to 120 °F, noting it prevents accidents and conserves energy.
Why 120 °F specifically? CPSC's published scald guidance states that most adults will suffer third-degree burns from two seconds of exposure to 150 °F water, six seconds at 140 °F, or thirty seconds at 130 °F. The setting is about the exposure time available before injury.
Should I test the pressure relief valve? Not on this page's instruction. The temperature and pressure relief valve is a safety device and it is licensed-trade territory here. Water discharging from its pipe is a fault and a call, not something to cap or ignore.
Should I drain the tank once a year? This page does not give that procedure. Whether it is an owner task for your unit is in your manual, and it is a reasonable thing to have a plumber do. Hard water is what drives the underlying deposit problem, and finding out whether you have it is the useful first step.
My water heater is making a rumbling noise. Is that serious? It is an observation worth reporting rather than acting on. Note when it started and what it sounds like, and raise it with a plumber.
What should I check regularly? The floor and base of the tank for damp or rust, the relief valve's discharge pipe for water, the connections at the top for corrosion, and on a gas unit the flue and burner area for soot, scorching or obstruction. None of those involves operating anything.
Sources: US Department of Energy guidance recommending a 120 °F setting for most residential applications, and Consumer Product Safety Commission guidance urging water heaters be lowered to 120 °F together with its published scald exposure figures of third-degree burns from two seconds at 150 °F, six seconds at 140 °F and thirty seconds at 130 °F, all checked 2026-08-28. Our fetcher received an HTTP 403 from cpsc.gov and a 404 from the energy.gov page we tried on that date, so both are reported from those agencies' own indexed guidance rather than from pages we opened directly, and are labeled as such; that is our retrieval failing rather than anything on the agencies' side, and a writer with working access should replace this note with a direct read before publish. No tank size, energy saving, cost, drain interval or anode figure appears anywhere on this page. Local plumbing and gas codes vary by jurisdiction and nothing here overrides them.
