 Ordinary 5 foot x 22" bathtub uses 20 gallon water. Use a bucket to measure after bath. Water heater thermostat set to 120°, typical bath 105° = 15-17 gallons hot water |
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 Not enough hot waterNo heater can produce 'endless hot water.' Every heater has limits, even when connecting 3 of them together. Truth is, the physics of heating water cannot be suspended just because a saleman has a quota, especially when incoming cold water is at it's coldest in winter time. The problem of getting enough hot water is solved by paying attention to: a) first hour delivery of heater b) peak usage. -First hour delivery
is the amount of usable hot water from a single continuous draw. This
number is on the water heater spec sheet available
at manufacturer's website. Take that number and subtract 20% for cold incoming water in winter.
-Peak usage is the busiest 2 hours when most hot is being consumed. For example if household takes 3 baths and 3 showers between 8-10 pm, that would be the two hour peak, resource Peak usage .pdf Folks should do a bit of research and number crunching, then install water heater that exceeds need .... ... or install 2 water heaters and plumb the heaters in series or parallel, resource Two water heaters ... or add a storage tank to the water heater, resource storage tank design ... or add a tempering tank, resource tempering tank ... or choose an AO Smith condensing heater, such as residential grade Polaris, resource Polaris spec sheet, ....or residential grade Vertex, Vertex spec sheet ... or commercial grade Cyclone 250 gallon, resource Cyclone spec sheet Cyclone large volume commercial heaters are nearly 8' tall, and are the commercial version of the Vertex. |
 Source: New-water-heater-rules/ pdf |
New energy standard April 2015 Over 55 gallon: More technology = more maintenance and higher cost 30-40-50 gallon ordinary tank: more insulation, larger size, higher efficiency, higher cost, but otherwise remain mostly unchanged after 2015 energy standard. Electric water heaters over 55 gallon must be heat pump to meet energy standards Gas water heaters over 55 gallon must be full condensing If you are running short of hot water Calculate first hour Ways to increase hot water Two water heaters Troubleshoot electric heater Troubleshoot gas water heater Resources: AO Smith Water heater sizing & calculation .pdf Tankless-sizing-guide.pdf Restaurant-water heater-sizing.pdf Water usage data .pdf |
| How much hot water is needed? • 20 gallons per person for the first two persons. • 5 gallons per person for each person over the first two. • 10 gallons for each full bath over the first bath. • 10 gallons for an automatic dishwasher. • 20 gallons for an automatic clothes washer." Personal note: we have 2 person household, 30 gallon heater, and wait 20 minutes between shower-bath, reduce consumption, for example use cold water on laundry Ways to increase amount of hot water |
How much hot water from 30-40-50
gallon water heater? "usable storage is the usable quantity of water available from the tank before incoming cold water reduces temperature. • 30 gallon size gives 21 gallon. Typical 104°F bath 15-20 gallon Hot water. • 40 gallon size gives 28 gallon for two bath residence -or- one bath with an automatic clothes washer. • 50 gallon size gives 35 gallon draw for three bath residence -or- two baths with an automatic clothes washer." Tank size is usually more important than recovery capacity when large quantities of hot water are required in less than 3 or 4 hours. • When a whirlpool tub is part of the home equipment, it is suggested that the water heater storage tank capacity be selected based on the needs of the whirlpool tub. This method of tank sizing, will in most cases, cancel all statements above concerning tank sizing. • High flow or multiple shower head installations must be sized for at least a 20 minute draw. |
| Undersized
water heater works
more and wears out sooner. Oversized water heater wastes money. Lochinvar pointed out that undersized gas or electric water heater 'will wear out sooner, possibly twice as fast if usage is very heavy. The continual influx of cold water into heater will cause more stress on the steel tank.' AO Smith notes in their literature that undersizing a gas water heater can cause 'excessive condensation that will corrode the heater faster. The flue tubes, baffles, and burners are susceptible to hydrocarbons in condensate (moisture created inside the vent) and carbonic acid. Continual exposure will weaken the flue tubes. Condensation can also spoil combustion and produce a carbon monoxide hazard. Read about CO detector and vent test  Solutions if heater is too small: 1) Reduce consumption, 2) Use tempering tank to preheat incoming cold water, Tempering tank 3) Inspect anode rod frequently to prevent rusted tank, Replace anode rod 4) Inspect for leaks at least once a year Leaking water heater 5) Make sure water pressure does not exceed 50 psi to reduce strain on tank Read about thermal expansion 6) Two water heaters Read about two water heaters 7) Research first hour delivery of new water heater Calculate first hour |
 Energy factor is not efficiency Energy factor is a formula for calculating efficiency Source for efficiency/ pdf Chart shows typical tank-type gas water heaters gained 2% efficiency over prior years. This might save $12-15 per year operation cost. Will it pay back the higher cost of heater plus more raw materials consumed during manufacture? All costs are energy, and new heaters have one-time up-front cost: they use more materials, arrive in larger boxes, take up more space and cost more to buy. On the back end, they cost more to replace. What is the real energy savings if a heater saves $12-15 per year, lasts 12 years for a total saving of $144, but consumes more raw materials to manufacture and costs $200 more to buy just to claim higher efficiency? |
 See example chart |
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Sizing chart Take showers instead of bath. Save 10 gallons hot water each time. To achieve same hot water consumption as previous heater without buying more expensive heater install 2 water heaters, cut consumption, maintain heater, turn up thermostat temperature Resources: Two water heaters 9 ways to save with water heater Maintain water heater How to adjust thermostat Ways to increase hot water Calculate first hour delivery |
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Chart shows three things: 1) First hour delivery for typical gas and electric water heaters. First hour is the amount of hot water the tank will deliver before water turns cool. Summertime delivery will be higher since incoming water is warmer so tank can deliver more hot before the water turns cool. 2) Gas will supply more hot water with smaller tank / gas heats water faster than electric 3) Homes with electric heater and 5 or more people require 80 gallon Heat pump, or two 40 gallon water heaters, since standard electric heaters are no longer made in 80 gallon size. |
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How many gallons might be needed for
first hour? For large bathtub, use 80 gallon first hour Resources: How to adjust temperature How to increase amount of hot water How to maintain water heater |
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Recovery
is a factor for first hour delivery First hour = 70% tank size X recovery + degree rise in temperature. 40 gallon electric water heater with 5500 watt element x .7 = 28 gallons Thermostat set to 130°F. Incoming summer water temperature 60°F, then rise in temperature = 70°. Chart shows 33 gallons for 5500 watt elements. 28 + 33 = 61 gallons Result shows: If you install 5500 watt elements on typical 4500 watt residential water heater, it will increase first hour delivery If you buy 40,000 BTU heater instead of 30,000 BTU, it will increase first hour delivery |
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 Avoid oversized bathtubs. It's not cheap to heat all that hot water. Buy a spa. Drive to ocean and support tourism. |
Large
bathtub / whirlpool tub Recommend 80 gallon first hour delivery Electric: minimum 60-to-80 gallon size just for that one tub Gas: minimum 50 gallon size just for that one tub Electric heat pump water heaters generally cannot produce enough hot water. Tankless promise unlimited hot water, but temperature of water is 120 F and water in tub may be cool by time tub fills. Cost of maintenance and repairs never pay back. All costs are energy Troubleshoot Rheem tankless Turn up thermostat on any water heater to increase amount of available hot water Resources: How to adjust temperature How to increase amount of hot water Cost to run water heater |
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Do you need that much hot water? |
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Set rain barrel higher than 550 gallon tank Use bulkhead fitting to tap into rain barrel Use 1-1/4" PVC water line to connect rain barrel to tank Tank must be on flat concrete pad. Cover top of rain barrel with hardware cloth to protect animals from falling into tank. Use gutter to channel water to rain barrel. Pour bath water into 55 gallon barrel using 5-gallon buckets Low pressure water timer |
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What is water worth? If you had to carry each gallon from the river up to your 2nd floor bathtub, when would you start to conserve? Average home uses 1/2 acre-foot water per year. 135,000 gallons = 27,000 5-gallon buckets Read about growth and electric consumption |
 How to adjust temperature on water heaters |
 How to install gas water heater Troubleshoot gas water heater Troubleshoot electric water heater |
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Support
the economy: Buy water heaters from my associate links: 50 gallon Gas water heaters at Amazon 40 gallon gas water heaters at Amazon 50 gallon Electric water heaters at Amazon 40 gallon electric water heaters at Amazon Hybrid / heat pump/ water heaters at Amazon Resources: How to install gas water heater How to install electric water heater Troubleshoot gas water heater Troubleshoot electric water heater Point of use water heaters |
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