When a water heater gives out, most people replace it with a tank that matches the old one's gallons. That can work, but gallons are only part of the picture. The right water heater size for a South Jordan home depends on your busiest hour of hot water use. It also depends on how cold the incoming water gets in winter and where the new unit has to fit.
First-Hour Rating vs Tank Gallons
A storage tank has two sizing numbers. The first is capacity, the gallons the tank holds. The second is the first-hour rating, which ENERGY STAR describes as how much hot water the unit can deliver during a busy hour under standard test conditions.
The first-hour rating is the better guide. It reflects both the stored hot water and what the burner or elements can reheat during that hour. Two tanks with the same gallons can carry different ratings, so a better model can deliver more hot water without a bigger tank.
When you compare water heater size options, read the first-hour rating on the label or spec sheet first. Then match it to your household's busiest hour, not to the number of bedrooms.
Why Hot Water Runs Short, Especially in Winter
Inside a tank, hot water rises and cold water sinks. When a tap opens, hot water leaves through the outlet at the top. Cold water enters through the dip tube, a pipe that carries it to the bottom. As the draw goes on, the cold layer climbs toward the outlet. Once it gets there, the shower turns lukewarm, even though the tank is still full of water.
The burner or heating elements rebuild that hot layer, but only at a fixed rate. If the household draws hot water faster, the tank loses ground until the busy hour ends.
Winter widens the gap. As one manufacturer's sizing guide explains, incoming water temperature changes with the season. In northern Utah, colder winter supply water needs more heat per gallon, so a tank recovers more slowly. A heater that keeps up in August may fall short on the coldest mornings.
What You Can Check Safely Right Now
Start with your current heater. Its nameplate or yellow EnergyGuide sticker lists the capacity, and many labels show the first-hour rating too. Then map your busiest hour of hot water use:
- Showers and tubs: count back-to-back showers and any soaking tub, which pulls a large volume at once.
- Appliances: note whether the dishwasher or clothes washer runs on hot water in that same hour.
- Seasons: note whether hot water runs short mainly in winter.
- Changes ahead: list any new bathroom, added family members or a finished basement.
Keep the check to labels, faucets and a notepad. Burner covers, element panels and the relief valve are for a technician. Your peak-hour notes are the most useful input for choosing a water heater size.
Sizing a Tankless Water Heater by Flow Rate
A tankless unit has no stored reserve, so it is sized by flow rate in gallons per minute. ENERGY STAR's tankless guidance lists average flows of 2.5 GPM for a shower or tub, 3.3 GPM for a clothes washer, 2.2 GPM for a sink and 1.3 GPM for a dishwasher.
Add up the fixtures that run at the same time. Using those averages, one shower plus the clothes washer comes to 5.8 GPM. Two showers plus the dishwasher come to 6.3 GPM.
Next comes temperature rise, the gap between the incoming water and your set temperature. The manufacturer guide linked above says to figure it for the coldest days of the year. A unit that handles plenty of flow at a small rise delivers less when the rise is large. For tankless water heaters, flow plus winter rise is the real water heater size question.
Space, Venting and Fuel Before You Upsize
A bigger or different unit has to fit the room and the systems behind it. Many homes keep the water heater in the basement near the furnace, and that space sets limits.
- Gas supply: ENERGY STAR notes that an installer should confirm whether the existing gas line can serve a tankless unit.
- Venting: gas condensing models vent through PVC pipe and need a condensate drain, as ENERGY STAR's explainer describes.
- Heat pump models: ENERGY STAR says these need an interior space that stays between 40 and 90 degrees Fahrenheit year-round, with 1,000 cubic feet of air around the unit.
The water heater choices that make sense depend on these limits as much as on demand. A larger water heater size only helps if the space and venting can support it.
A South Jordan Scenario You Might Recognize
Picture a family whose teenagers now shower back to back before school. The gas tank in the basement handled the house fine a few years ago. Now the third shower of the morning turns lukewarm, and on winter mornings it happens during the second one. By midafternoon the water is hot again, and the burner lights normally.
That pattern points to peak-hour demand outgrowing the heater's first-hour rating, not to a broken heater. The household changed, and colder winter water made the gap show up sooner.
Now change one detail. The water turns lukewarm a few minutes into the first shower, even on a quiet day. That points to a fault, such as a broken dip tube or heavy sediment, which a repair may fix without a new size.
Safety Notes
- Gas smell: if you smell gas near the water heater, get everyone outside, then call 911 or the gas utility's emergency line from outside.
- Carbon monoxide alarm: if a CO alarm sounds, get everyone outside, then call 911 from outside.
- Setpoint: a bigger tank is not a reason to turn up the heat. The CPSC recommends 120 degrees Fahrenheit to reduce the risk of tap water scalds.
- Relief valve: leave the temperature and pressure relief valve and its discharge pipe alone. The ICC's code notes explain why that pipe must not be capped or plugged.
- Clear space: keep boxes, laundry and anything flammable away from a gas water heater and its vent.
- Covers and wiring: leave burner covers and electric element panels closed, since they guard flame or live wiring.
When to Call a Professional
Call when a sizing change also means a new fuel, a new vent or a new location. Moving from a tank to tankless, trying a heat pump model or stepping up a size can change the gas line, the venting and the electrical needs. Those are installer decisions, not guesses.
Also call when the symptoms point to a fault rather than demand. Water that turns lukewarm fast, a leak at the tank, a relief valve that discharges, or rumbling and popping from the tank all need a closer look. Replacing a heater that only needed a repair adds no hot water.
Towers Plumbing can review water heater size with your notes in hand. A technician can also look at the space, gas line and venting in homes across South Jordan and nearby communities.
Frequently Asked Questions
Does household size decide the water heater size?
It helps, but habits matter more. Back-to-back showers, a soaking tub or laundry during the morning rush all raise peak demand, so size to that hour rather than to headcount.
Should I just buy a bigger tank?
Not by default. A bigger tank keeps more water hot around the clock, so it loses more heat while it sits and takes more floor space. If a same-size model's first-hour rating covers your busy hour, upsizing adds little.
Can I replace my old tank with the same size?
ENERGY STAR's buying guidance says that if your current heater meets your needs most of the time, you can probably replace it with one the same size. Compare first-hour ratings, since a newer model may deliver more.
How is a tankless unit sized for Utah winters?
Use your highest combined flow and the largest temperature rise, which comes on the coldest days. That manufacturer guide notes there is no benefit to oversizing, so aim for a match, not the biggest model.
Note Your Busiest Hour, Then Reach Out
Before you call, write down what you know. Note the capacity and first-hour rating from your heater's label, whether it runs on gas or electricity, and its age if the label shows a date. Add how many showers happen in your busiest hour, when the dishwasher and washer run, and whether hot water runs shorter in winter. Photos of the label, the vent pipe and the space around the heater help too.
Then contact Towers Plumbing through our contact page to set up a visit. With your notes in hand, a technician can talk through the right water heater size for your household, check the space and venting, and explain the options before any work begins.