Water Heaters - Whole House
Storage Tank Water Heaters

Storage tank water heaters are the most common type of residential whole-house water heater.

As the name implies, they heat and store hot water for future use.

In addition to providing hot water for entire households, storage tank water heaters can be used as supplemental water heater for high demand showers, spas and other fixtures.

How It Works: (Gas, LP, Electric, Oil)
When you turn on a hot water faucet or use hot water in a dishwasher or clothes washer, water pipes draw hot water from the tank.

The heated water is drawn from the top of the tank and is replaced by cold water that is carried to the bottom by a dip tube.

When the thermostat signals that the water temperature has dropped, a burner (gas or oil) or heating element (electric) starts up to heat the water.

Pressure Relief
As water is heated, it expands. This builds pressure within the tank.

Every water heater must be protected by a pressure-relief valve mounted at the top of the heater, and these valves should always be replaced when the water heater is replaced.

If a there is no check valve, pressure reducing valve, or other device blocking the inlet to the water heater, the increased water volume simply travels back into the source. However, if the inlet is blocked, this pressure can build to dangerous levels.

The relief valve relieves this pressure by discharging sufficient water to bring the pressure down to acceptable levels. If you don't want a pressure relief valve to release this water, you would need to install a thermal expansion tank in the water line to absorb the expansion

Dip Tube
The dip tube is a long slender tube that fits down into the water heater inlet. The dip tube directs the incoming cold water down to the bottom of the tank.

If the dip tube is broken, the incoming cold water can mix with the out going hot water and cause it to seem as though the water heater is running out of hot water.

If these tubes are defective, they can corrode, releasing tiny particles of plastic and sludge through the plumbing system. This in turn can clog the faucet aerators and screens causing low water pressure at the fixtures.

The fuel type or energy source you use for water heating will not only affect the water heater's annual operation costs but also its size and energy efficiency.

Electric Powered Models
Probably the least expensive tank-type water heaters to purchase and install, electric-powered models are a favorite with builders and installers in areas where alternative fuel sources are unavailable.

Electric models heat water directly by using electric elements submersed inside the tank. The elements are placed one low and one high in the tank to distribute heat more evenly throughout the stored water.

• Clean, no venting materials or fuel lines required
  
• Easy to service and maintain
  
• Low initial purchase and installation cost
  
• Relatively unaffected by sediment build-up
  
• Higher operating costs than gas or oil models
  

Efficiency
Recent regulatory changes have made electric water heaters much more efficient thereby making the product class a better value.

The most efficient electric storage water heaters have energy factors ranging between 0.93 and 0.95, resulting in estimated annual energy use below 4,725 kWh/year. Look for the most efficient electric resistance unit in your size range.

There is little difference between the most efficient electric resistance storage water heaters and the minimum efficiency standard. If you use electricity for water heating, consider installing a heat pump water heater which uses less than half as much electricity as conventional electric resistance water heaters.

Gas, Propane and oil-fired water heaters heat the tank, which in turn heats the water. This type of system provides more hot water, and a faster recovery rate (reheating time) than electric water heaters.

• Low initial purchase and installation cost
  
• Years of excellent service even in areas of hard or corrosive water
  
• Models vary from standard to high input and high recovery designs
  
• Low maintenance, many offer self-cleaning features
  
• Lower operating costs when compared to electric units
  

Oil-Fired Models
Though somewhat limited geographically by its fuel source, oil-powered water heaters have a solid reputation for rugged durability and high output.

Oil-powered water heaters are known for their ability to heat water faster than other fuels and offer a low cost option when natural gas is unavailable.

The process of operation is very similar to that of a conventional gas-powered water heater with the most obvious difference being the oil burner itself.

Unlike a gas-powered water heater with an integrated combustion chamber situated directly under the water storage tank, the oil burner is attached to the front of the water heater and propels a flame into a separate chamber. This provides service technicians with easy access to oil burners, which are, by design, more complex than gas burners.

• Oil-powered models heat water three to four times faster than other fuels
  
• The best choice for homes with existing oil service
  
• High output, rapid recovery and reliable performance
  
• Highly efficient, energy saving, clean and reliable
  
• Years of excellent service even in areas of hard or corrosive water
  
• Highest maintenance/operating costs
  

Efficiency
The most efficient gas-fired storage water heaters have energy factors ranging from 0.60 to 0.65, corresponding to estimated gas use below 250 therms/year. Condensing water heaters have energy factors as high as 0.86.

Heat Loss
Because water temperature is constantly maintained in the tank, energy can be wasted even when a hot water tap isn't running. This is called standby heat loss.

The burner on a traditional storage tank water heater does NOT burn 24 hours a day.

Storage water heater models with heavily insulated tanks, significantly reduce standby heat losses, lowering annual operating costs. The high-performance foam insulation keeps the water hot for many hours before the heater needs to turn back on to raise the temperature.

Look for models with tanks that have a thermal resistance (R-Value) of R-12 to R-25. If you don't know your water heater tank's R-value, touch it. A tank that's rather warm to the touch needs additional insulation. Insulation jackets are used on older, inefficient electric heaters. These pre-cut jackets or blankets are available from around $10 - $20. Choose one with an insulating value of at least R-8.

Never use an insulation jacket on a gas water heater unless the manufacturer specifies that it is safe to do so. If the insulation jacket should slip or come off of the gas water heater, it could pose a fire hazard if it comes in contact with the burner, pilot light, or other hot surfaces.

• Fan-Assisted
  uses a draft-induced fan that regulates the air that passes through the burner, which minimizes the amount of excess air during combustion, increasing efficiency.
  
  
• Atmospheric Sealed-Combustion
  Uses a combustion and venting system that is totally sealed from the house.
  
  

In very tight houses, drawing combustion air from the house and passively venting flue gases up the chimney can sometimes result in back-drafting of dangerous combustion gases into the house.

Typically, the vent is a vertical pipe that extends through the roof of the home via an existing chimney or furnace exhaust pipe.

Look for Sealed Combustion or Power-Vented Systems:
For safety as well as energy efficiency, look for gas- or oil-fired water heaters with sealed combustion or power venting.

Sealed combustion means that outside air is brought in directly to the water heater and exhaust gases are vented directly outside. The combustion is totally separated from the house air.

A power-vented system offers the option of venting vertically, horizontally or via a combination of both methods.

This flexibility allows for placement of the water heater in the most advantageous location and does not require the unit to be installed near an existing chimney or furnace exhaust pipe.

Having dedicated venting automatically ensures that the vent pipe can handle the products of combustion (exhaust gases) safely.

Flammable Vapor Ignition Resistant (FVIR)
Current designs expose burner flames to household air, including any flammable vapors that might result from an accidental spillage of gasoline or paint thinner. That could result in catastrophe should these vapors come in contact with the combustion flame.

In an effort to safeguard the home against this risk, a new type of combustion changer has been developed that traps inlet air and keeps burning vapors from escaping into the room where a fast-spreading fire may result.

Flammable Vapor Ignition Resistant (FVIR)
These changes will have a direct impact on consumers. The cost of these new units will be considerably higher than existing units, possibly as much as 50%.

Other information useful information includes the annual energy usage and also a national average unit cost of fuel.
Click here to learn how to read this label.

Efficiency Rating
Models with higher energy efficiency or energy factor (EF) may cost more initially but they will save you money over years of reliable service.

Energy factor is based on recovery efficiency, standby heat loss and other factors.

The energy factor of any water heater is expressed as a percentage. A higher percentage means a water heater with better fuel efficiency. When all else is equal, ask your professional installer for a water heater with the highest energy factor.

BTU Input
The BTU input is a measure of the regulated gas flow rate that the heater utilizes to heat water in the storage tank. The higher the BTU input the more powerful the water heater.

The more powerful the water heater, the more usable hot water will be generated from the same size (gallon capacity) water heater.

BTU inputs vary from water heater to water heater and manufacturer to manufacturer. A good rule of thumb is to select the water heater with the highest available BTU input in your desired gallon capacity. This will provide more hot water for your money.

First Hour Delivery
One of the most important considerations when selecting the right water heater is First Hour Delivery (FHR) - or the number of gallons of hot water available in the first hour of operation. A bigger storage tank doesn't always equate to a higher FHR.

Peak-Hour Demand
When considering a water heater, your household's peak-hour demand must be determined. Select a model with an FHR that meets or exceeds that number.
The FHR of every water heater can be found on the Energy Guide Label.

Do the following to estimate your peak hour demand:

• Determine what time of day (morning, noon, evening) you use the most hot water in your home. Keep in mind the number of people living in your home.

• Use the worksheet below to estimate your maximum usage of hot water during this one hour of the day—this is your peak hour demand. Note: the worksheet does not estimate total daily hot water usage.

The worksheet example shows a total peak hour demand of 70 gallons. Therefore, this household would need a water heater model with a first hour rating of 68 to 72 gallons.

Compare the total gallons needed with the recovery rate on the heater you are considering.

For example, if you have a family of four and both adults take a shower in the morning while the children wash up and brush their teeth, by the time breakfast is finished, the family will probably have used nearly 40 gallons of hot water. This would require a minimum of a 40-gallon heater.

Water temperature will start to drop as hot water is drawn from it. Consumption demands have a habit of growing with time, and with modern bath equipment becoming more luxurious, the needs for an ever-increasing supply of hot water is evident.

In general, the more bathrooms and occupants in your home, the higher the capacity of your water heater should be. Likewise, if you have a large family, or are particularly active you may need a larger size water heater.

An oversized whirlpool or full-body shower may require a dedicated water heater. Consult your plumbing contractor or dealer before purchasing.

Self-Cleaning Device
Many tank-type water heaters offer a self-cleaning device of some kind.

The purpose of these devices is to reduce the accumulation of sediment at the bottom of the water heater.

In hard water areas, accumulated sediment can be severe and negatively impact the performance efficiency of the water heater, and causing premature tank failure.

Tank Lining
Almost every tank utilized in a conventional water heater is made of steel. To counteract the corrosive effects of hot water, the steel needs to be protected or lined in some way.

Most tanks are lined with glass. Some manufacturers use a porcelain-like coating on the inside of the steel tank.

Water Heater Catch Pan
The average life expectancy of a hot water heater is 10 to 12 years ... and when they fail, the cause is usually due to a cracked or ruptured glass tank liner.

When that happens, the contents of the tank is going to go someplace in your home ... that's 30 - 100 gallons of water, depending on tank size ... assuming of course that you are there to turn off the water going into the tank.

According to a recent nationwide analysis by Safeco Insurance, one out of every 10 water-damage claims can be traced back to a malfunctioning hot water tank or washing machine. These two appliances are more likely than Mother Nature to inflict damage on the home.

A water heater catch/drain pan provides an extra level of protection against water damage. Made of aluminium, the pan is 2" deep and is fitted with a 1" side or bottom drain outlet.

Available in 14", 16", 19", 22", 24", and 26½" diameters to help protect any installation area from possible water damage.

The water heater drain/catch pan must be installed at the same time as the water heater. It cannot be added later, without removing the water heater.
(note: catch pan must conform to local building codes)

When using a catch pan, direct water to floor drain A garden hose attached to the catch pan should direct water to a floor drain. Use extreme caution when draining to a sump pit To avoid damage to the sump pump, the pump must be rated to handle the amount of flow and the temperature of the water. A cast iron motor housing will withstand higher temperatures than a pump with a plastic motor housing. Zoeller Sump Pumps with cast iron motor housings have a maximum water temperature rating of 130° F. Zoeller Sump Pumps with plastic motor housings have a maximum temperature rating of 110°F. Under no circumstances should water from the water heater exceed the sump pump manufacturer's maximum temperature rating.

Warranties
Water heater warranties vary by model in duration (5-10 years), coverage (workmanship, parts & labor) and by the conditions that must be met to keep the warranty in effect.

Generally, the more expensive the water heater, the longer the warranty.

Basic residential water heater warranties are relatively consistent regardless of manufacturer. Some manufacturers offer an extended warranty package, that extends the basic warranty on most residential tank-type models to a full ten years.

Installation
Even though installing a hot water heater may seem rather simple, the simple fact that it involves plumbing, gas, electric, open flame and carbon monoxide, it is recommended that an experienced professional plumbing or heating contractor perform the installation

A professional will help you choose the right water heater for your application. In addition, they will they install it correctly and back their workmanship.

Water Heater Concerns
Water temperature, color noise, and hammer are all problems associated with water heaters. In most cases, the solutions are relatively simple.

Not Enough Hot Water
Some homeowners turn up their hot water heater thermostat to increase the availability of hot water when they really need a larger (or new) water heater. This can be extremely dangerous to small children and elderly or disabled persons.

The factory setting on new residential water heaters is 120 degrees Fahrenheit. This is the highest setting considered to be safe; higher temperatures can cause severe scalding. Click Here to read more about the dangers of scalding, burns and anti-scald devices.

There can be many reasons your water heater is not producing enough hot water.

It may simply be undersized for your needs. Analyze the demands you place on the system and compare them to the rating of your heater. You may find that it is not designed to provide the amount of hot water you're trying to extract from it.

Water Heater Noise
As water heaters age, particularly in areas where there is hard water, calcium carbonate can precipitate out and settle to the bottom of the heater in the form of sediment.

As the burners heat the bottom of the tank, steam bubbles form under the sediment just as they do in a pot on your kitchen stove. The steam bubbles escaping from under the sediment create the thumping and popping noises you sometimes hear coming from your water heater.

This build up of sediment can also reduce the efficiency of your water heater and reduce its holding capacity. Regular flushing of the water heater through the drain valve can help prevent sediment build up. Sediment reduces the efficiency of the water heater and may clog pumps and valves elsewhere in the system.

Condensation often occurs on water heaters when a large hot water draw occurs and a large amount of cold water enters the water heater. Sometimes this condensation can be mistaken for a leak in the tank. In addition, this condensation can collect at the bottom of the heater and drip onto the hot burner, causing a sizzling noise. This is not generally harmful.

Water Hammer
Water traveling through the pipes contains kinetic energy. The sudden closing of a valve causes a shock wave in the system, which results in a hammering sound in the pipes.

This is not only annoying, but it's also potentially damaging to the plumbing system. This occurs most often with solenoid valves.

Water hammer arrestors are available to combat this problem. They resemble a cylindrical container with a small air bladder inside, installed near the valve causing the problem. The air bladder cushions the force of the flow of water, thus softening the impact.

Occasionally, a sagging water pipe will behave the same way, and installing hangers or clamps can help to reduce the problem.

Milky Water
Water contains dissolved oxygen and other gases.

The capacity of water to hold gas is determined by atmospheric pressure. At normal atmospheric pressure, when water is heated, it releases some of these gases because it has less capacity to hold them.

However, a water tank is a sealed environment, so as the water is heated, pressure builds up in the tank, artificially holding these gases in their dissolved state. When water is drawn from a faucet and released from the tank, the pressure is lowered, causing these gasses to vaporize and form tiny bubbles in the water, giving it a milky appearance.

These bubbles are harmless, and if you let the water stand for a few minutes these bubbles will rise out of it and the water will clear up once again.

Earthquake Risk
A 50-gallon water heater holds about 400 pounds of water.

It could also cause a good deal of water damage should the tank lose its contents in the fall. A falling water heater could damage the water pipes and create a costly plumbing repair bill in addition to the water damage.

It could also waste valuable water when local firefighters need every available drop of water to fight the inevitable fires that can accompany earthquakes.

All of these consequences can easily be avoided.

Water Heater Strap Kits
Water heater strap kits are available and sometimes even required by local building codes. These are not expensive and will secure the tank in place and prevent the kind of damage mentioned above.

To read more about these as well as other topics of general interest concerning water heaters, please refer to Rheem's technical bulletins.

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