Brand exhibit · Super Arbor
From galvanized steel drums in Emeryville, 1925, to automatic gas water heaters by 1931 — one hundred years of keeping the water hot.
Styled visualization — illustrative reconstruction, not Rheem product photography. Machine-readable facts.
Room I
Eight exhibits, one century.
Exhibit 01 — 1925
Brothers Richard and Donald Rheem established the company in Emeryville, California, galvanizing steel drums and other metal products for the petroleum trade — a third brother, William, is named among the founders in Rheem’s own centennial telling. The family name has been on the product ever since — first on drums, soon on tanks.
Exhibit 02 — 1931
Six years in, Rheem acquired the John Wood Manufacturing line and began producing automatic gas storage water heaters. Water heating became the company’s defining trade, and its own timeline notes the focus has continued to the present day.
Exhibit 03 — 1947
Rheem purchased the Fraser line of gas furnaces and winter air conditioners, anticipating a market for central heating and cooling. The Rheemaire central air system followed in 1956, and HVAC has run alongside water heating in the catalog ever since.
Exhibit 04 — 1960
Rheem purchased Ruud Manufacturing’s water heater business, gaining a broader commercial line, a second distribution network, and — in the company’s words — a second respected brand name. Ruud remains a sister nameplate in the Rheem family today.
Exhibit 05 — 1988
Rheem became a wholly owned subsidiary of Paloma Industries of Japan, one of the world’s leading producers of gas appliances, as the company’s centennial timeline records it. Operations continued under the Rheem name, and headquarters moved to Atlanta, Georgia, in 2007.
Exhibit 06 — 2009
Per Rheem, the company was first to launch a hybrid heat pump water heater, rated at more than twice the efficiency of standard electric models. Over the following decade, heat-pump water heating moved from novelty to a mainstream residential category.
Exhibit 07 — 2020
Rheem introduced ProTerra, the hybrid electric heat pump water heater it describes as the industry’s most efficient, with models rated up to 4.07 UEF. A condensing tankless line had joined the catalog in 2010, rounding out three ways to heat water.
Exhibit 08 — 2025
Rheem marked a century in business — from galvanized drums in Emeryville to water heating and air systems sold worldwide. The company’s centennial telling counts more than 500 patents and an unbroken line of water heaters built since 1931.
Room II · Interactive interlude
Pull the light across the corner. Draw the tank down, let it recover — the hottest water stays stratified at the top for the outlet.
First hour, drawn: 0 gal
Illustrative simulation, not a rating
Drag to orbit · use the exhibit controls
Room III · Interactive exhibit
A storage water heater, separated into the parts the spec label never mentions. Use the layer control to open it — the numbered plates cite their sources.
The assembly
Jacket → foam insulation → the lined steel tank — and inside it the anode rod, the dip tube, the elements, and the T&P valve on the wall. Open a numbered plate to inspect a part; the rest of the machine steps aside.
Stylized CGI rendering — an illustration of tank construction, not a Rheem drawing.
Room IV
A magnesium or aluminum rod threaded into the tank corrodes on purpose: its metal gives up electrons more readily than steel, so water attacks the rod instead of the tank wall. Rheem’s parts guidance calls anode rods the most important line of defense in extending tank life and preventing leaks — and notes that a depleted rod protects nothing. Inspection is on every use-and-care schedule.
Styled visualization
Room V · Read the label
Every storage water heater carries the same three numbers — gallons, first-hour rating, and UEF. Only one of them sizes your house.
50 GAL FHR 62 UEF 0.93 4,500 W
Rated capacity is the water the tank physically contains — in Rheem’s EnergyGuide explainer, “the actual amount of water the unit contains.” It is the least useful number on the label for sizing: two 50-gallon units with different burners or elements deliver very different amounts of hot water in an hour. Gallons describe storage, not delivery, and buying by gallons alone is the category’s classic mistake.
DOE defines first-hour rating as the maximum gallons of hot water a fully heated tank can supply within one hour — stored volume plus recovery rate combined. It prints on the yellow EnergyGuide label required on storage water heaters. DOE sizing guidance says to estimate the busiest hour’s hot-water demand and match FHR to it. This, not the gallon stamp, is the number that sizes a household.
Uniform Energy Factor, DOE’s 2017 metric, is the share of consumed energy that ends up as hot water over a 24-hour test; compare it only within the same usage bin, which is assigned by FHR. The trailing figure is recovery input: electric tanks list element wattage, commonly 4,500 W, while gas tanks list burner input in BTU per hour — typically 40,000 on 50-gallon residential models.
Size by the first hour DOE sizing guidance says to estimate the busiest hour’s hot-water demand and match FHR to it — this, not the gallon stamp, is the number that sizes a household.
Hybrids read differently: a heat pump moves heat from the air rather than generating it, so ProTerra-class units rate up to 4.07 UEF — an efficiency multiple, not extra stored gallons. Specimen figures are illustrative of a common 50-gallon electric label; individual models vary.
Room VI
“The company’s centennial telling counts more than 500 patents and an unbroken line of water heaters built since 1931.” — the record, Exhibit 08
Room VI · The families, explained
Three ways to heat water — standing inventory, on-demand flow, and the heat pump that moves heat instead of making it.
The standing-inventory model: a Rheemglas-lined steel tank keeps hot water ready around the clock, gas burner below or electric elements within. Rheem’s retail tiers carry Performance and Performance Platinum names; its contractor catalog runs Professional Classic, Classic Plus, and Prestige. Common residential sizes are 40 and 50 gallons, with short, tall, and larger formats around them; warranties run roughly six to twelve years by model. Read the first-hour rating before the gallon stamp.
The fit The like-for-like swap when fuel, venting, and floor space already exist.
No stored gallons: water heats as it flows, so output is rated in gallons per minute at a given temperature rise rather than capacity. Rheem’s condensing IKONIC gas line runs 8.4–11.2 GPM at 0.96 UEF; non-condensing RTG models rate 0.82 UEF; compact RTEX electric units run from single-fixture point-of-use sizes up to roughly 4-GPM models. Hot water is continuous within flow limits — but sizing, gas supply, and venting are a different exercise from tanks, and a specialist’s call.
The fit Tight spaces and households that outrun a tank’s first hour — sized in GPM and temperature rise.
A heat pump mounted on a storage tank: it moves heat from the surrounding air into the water instead of generating it — a method New York’s NYSERDA credits with around three times the efficiency of standard electric models. Rheem rates ProTerra models up to 4.07 UEF, with resistance elements as hybrid backup for heavy draws; per Rheem, that is up to 75 percent less energy than a standard electric tank. Supply-circuit, clearance, and air-space requirements vary by model.
The fit All-electric homes chasing operating cost; confirm circuit, height, and airflow first.
Sizing notice Size by first-hour rating, not tank gallons. DOE sizing guidance matches a tank’s FHR — the hot water it can deliver in a busy hour — to your household’s peak-hour demand; a bigger tank with slow recovery can deliver less. Fuel type, venting, gas line, circuit capacity, and drainage are local-code and licensed-installer territory — confirm before purchase.
Room VII · The desk’s read
The order logic nobody writes down — voiced as our desk’s read, not the brand’s claim.
The desk’s read: the maker is identical; the tier names track the sales channel. Performance-series tanks are the retail route, while Professional Classic and Prestige models list on Rheem’s own catalog and move through plumbing distributors. If a licensed plumber is installing anyway, price both routes before defaulting to either. Then compare the honest way — first-hour rating, UEF, and warranty term, model against model, not name against name.
The desk’s read: count your worst hour, not your bathrooms. Add back-to-back showers, the dishwasher, and a laundry cycle in the busiest sixty minutes, then buy the first-hour rating that covers it — DOE’s method, and the reason a 40-gallon gas unit can out-deliver a 50-gallon electric. Buying gallons instead of FHR is how cold showers get purchased at full price.
The desk’s read: the sticker is the down payment; UEF sets the monthly bill. Check the EnergyGuide label’s estimated yearly cost, then run it against your own utility rate before comparing prices. A heat-pump unit near 4.0 UEF against a resistance tank near 0.93 is the widest efficiency spread in the aisle — worth the arithmetic, and worth confirming the install requirements before the savings are spent.
The desk’s read: if you are replacing a failed tank, ask what killed it — tanks commonly fail by internal corrosion once the sacrificial anode is spent, which is the part’s whole job. Start the new one differently: put an anode inspection on the calendar per the use-and-care manual, flush sediment on the same schedule, and know where the T&P valve discharges. It is the cheapest ownership habit in water heating.
Put your busiest hour on a list — showers, dishwasher, laundry — and a specialist sizes the first-hour rating before you buy.
Room VIII · The working collection
Live catalog — priced in the open, the same number for everyone.
The working collection · I — The tank bench
Gas, electric, and hybrid — sized by first-hour rating, not the gallon stamp.
The gas tank
Performance 40 Gal. Short, 34,000 BTU Natural Gas
View current product
The electric tank
Marathon 50 Gal. Tall, 4.5kW 2-Element Electric
View current product
The big hybrid
ProTerra 80 Gal. Smart Heat Pump, Leak Detection
View current product
The 50-gal hybrid
Performance Platinum ProTerra 50 Gal. Heat Pump
View current product
The working collection · II — The system bench
Two tankless sizes, a point-of-use unit, and the control that watches the system.
The big tankless
IKONIC 199 MBH Condensing Gas Tankless
View current product
The mid tankless
IKONIC 157 MBH Condensing Gas Tankless
View current product
Point of use
6 Gallon Electric, 208V, Point of Use
View current product
The control
EcoNet Gen 3 Smart Thermostat
View current product
Asked at the desk
First-hour rating is the U.S. Department of Energy’s estimate of the maximum gallons of hot water a storage water heater can supply in an hour that begins with the tank fully heated — stored volume plus recovery rate combined. It appears on the yellow EnergyGuide label. DOE sizing guidance matches FHR to a household’s peak-hour demand, which makes FHR, not tank gallons, the number that sizes a home.
Uniform Energy Factor is the Department of Energy’s water heater efficiency metric, adopted in 2017 to replace the older Energy Factor. It measures how much of the energy a unit consumes becomes hot water over a standardized 24-hour test. Models are grouped into usage bins by first-hour rating, and UEF comparisons are valid only within the same bin. A higher UEF means lower operating cost for equivalent duty.
They are tier families sorted by sales channel. Performance and Performance Platinum tanks sell through retail — Home Depot listings carry them — while Professional Classic, Professional Classic Plus, and Professional Prestige appear on Rheem’s own catalog and through plumbing distributors. Specifications and warranties vary by individual model rather than by name alone, so compare first-hour rating, UEF, and warranty terms line by line.
ProTerra is Rheem’s hybrid electric heat-pump water heater line, introduced in 2020. It heats water by moving heat from the surrounding air into the tank — a method NYSERDA credits with around three times the efficiency of standard electric resistance — with backup elements for high demand. Rheem rates ProTerra models up to 4.07 UEF and, per its own figures, up to 75 percent less energy use than a standard electric tank.
The anode rod is a sacrificial magnesium or aluminum rod inside the tank that corrodes in place of the steel wall — its metal oxidizes more readily, so water consumes the rod instead of the tank. Rheem’s parts guidance calls anode rods the most important line of defense for tank life and leak prevention, and notes that a depleted rod no longer protects. Periodic inspection and replacement extend tank life.
Rheem Manufacturing Company was founded in 1925 in Emeryville, California, by the Rheem brothers, and has been a wholly owned subsidiary of Japan’s Paloma group since 1988. Its headquarters moved to Atlanta, Georgia, in 2007. The company entered water heating in 1931, added HVAC in 1947, acquired the Ruud brand in 1960, and marked its centennial in 2025.
The hall closes. The water stays hot.
The Rheem lines above are live catalog — priced in the open, the same number for everyone. Water heating is a sizing buy: send your busiest hour, and a human specialist checks FHR, fuel, and fit before you order.
Citations: Rheem centennial history (rheem.com/100) · rheem.com product pages & spec sheets · parts.rheem.com component guides · Rheem use-and-care manuals · U.S. DOE Energy Saver & ENERGY STAR · FTC Energy Labeling Rule · Paloma Rheem Holdings · retailer and distributor listings. Era and anatomy imagery: styled visualizations, not archival photographs or Rheem drawings. Prices as listed at superarbor.io at time of writing. Machine-readable facts, sources, and product data: rheem.brandlab.json.
Rheem®, Ruud®, ProTerra®, EcoNet®, Rheemglas®, and related marks are trademarks of Rheem Manufacturing Company. © 2004–2026 Rheem Manufacturing Company. All rights reserved. Super Arbor is an independent retailer; brand marks remain the property of their respective owners.
