Posted on: November 15, 2013
By: Alan O'Neill
Posted in: Plumbing
Jumping into the shower and finding out the cold way that your water heater isn’t working properly can be a real wake-up call. The water coming into your home from underground pipes is usually cold (maybe even glacial depending on the time of year). To have warm water to take a shower or use your washing machine, you need a water heater.
The average home in the U.S. has a water heater with a tank. Each person in the home uses roughly 10 to 20 gallons just to take a shower, brush their teeth and wash their hands each morning – that’s a lot of water. The tank capacity can be anywhere between 30 gallons and 80 gallons, so running out temporarily may happen.
The old, reliable water heater that’s most familiar in the U.S. today is a relatively simple appliance. It’s just a cylindrical drum filled with water with a heating mechanism on the bottom or inside. The simple design shrouded in its wooly insulating blanket exploits the rising heat to deliver hot water right to your faucet with a minimum of effort.
Most hot water heaters have a lifespan of 10 to 15 years. The water heater’s efficiency begins to decline in part because internal parts are corroded or encased in a buildup of minerals. Flushing the hot water heater regularly keeps it working longer and more efficiently. A few noticeable changes in your heater will let you know it’s time to purchase a new one before it fails completely.
If the pipes are the leaky culprits, your certified plumber can repair the pipe instead of replacing the entire water heater. If you do need to replace the heater, now is the time to do your research. Your certified plumber can help you decide on a replacement system. You’ll have to live with it for a quite a while.
When you replace your water heater, you have a number of choices. Of course, first you’ll have to decide what type of water heater you need. Common options are tank less or demand-type water heaters and storage and heat pump (with a tank) water heaters. There are also combination water and space heating systems; you’ll need to consult a qualified contractor for more information.
To size tank less or demand-type water heaters, you need to determine the flow rate and the temperature rise you’ll need in your home. List the hot water devices you expect to use at any one time (shower, kitchen sink, etc.). Then add up their flow rates (gallons per minute). This is the total flow rate you’ll need. To reduce flow rates, install low-flow water fixtures. To determine the temperature rise, subtract the incoming water temperature (usually about 50 degrees) from the desired output temperature (usually about 120 degrees). On average, you’d need a demand water heater that produces a temperature rise of 70ºF (39ºC). For dishwashers without internal heaters you’ll probably need a higher output temperature. Most demand water heaters are rated for a variety of inlet temperatures. Some tank less water heaters are controlled by a thermostat. They can vary their output temperature according to the water flow rate and inlet temperature. Tank less water heaters may get expensive, but they are also not limited by the tank capacity. Tank water heaters also cost more in energy bills because they continually heat the water, even when it’s not being used. Tank less water heaters also save space. There are also new hybrid heaters and mixing valves that can increase the output that we can now use where in the past larger (and more expensive) heaters were needed.
To properly size a storage water heater (including a heat pump water heater with a tank), use the water heater’s first hour rating. The first hour rating is the number of gallons of hot water the heater can supply per hour starting with a tank full of hot water. The water heater capacity depends on the tank size, source of heat (burner or element), and the size of the burner or element. The EnergyGuide label lists the first hour rating as “Capacity (first hour rating).” Product information supplied by the manufacturer should also provide the first hour rating. You’ll need a water heater with a first hour rating that matches your peak hour demand. To estimate your peak hour demand, you should determine what time of day you use the most hot water and estimate your maximum usage of hot water during this particular hour of the day.
A properly sized water heater should meet your home’s hot water needs while operating efficiently. Make sure your new heater is the correct size and type to meet all of your needs before you buy one. Your certified plumber can help you determine which system is best for your home. They may also have specials on equipment or other services. They may also have service plans, like The Abacus Club, that can help save you money on service calls or installation.