Hot Water Tank 101: Pros and Cons, How to Flush and Maintain It
Did you know that your hot water tank is the second largest expense in your home, accounting for up to 18% of your utility bill? You don’t have to believe us; the Department of Energy (DOE) says so. While we all enjoy a soothing hot shower, the adverse environmental impact and the rising energy costs say it’s time to take a closer look at various energy-efficient options available.
Types of Hot Water Heaters
There are various kinds of hot water heating systems, so today we will talk about the pros and cons for three of the most popular types on the market. If you’re looking to upgrade your system, do you research beforehand to find out which option best suits your needs.
- Storage Tank – This is the most common hot water system used in American homes. Electricity, natural gas, propane, or oil is used to keep the water constantly heated in the storage tank. Turning a faucet on draws the hot water out of the top of the tank and cold water flows in the bottom to replace it.
- Tankless – Also known as on demand water heaters, these systems use electricity or gas to heat the water. Tankless water heaters do not require a storage tank to get the water ready for your hot shower.
- Solar – Water circulates from the tank through a solar collector where the sun heats it for household use. One of the more recent technologies, a solar water heating system might also require a conventional water heater. If the sun did not warm the water enough, the second system can bring it up to the desired temperature.
- Heat Pump – Heat pumps use electricity to transfer heat instead of generating heat directly. You can use heat pumps for water heating alone, or in combination with your air conditioning and heating system.
Tankless Hot Water Heaters
Available in natural gas, propane, and electric models, tankless water heaters are generally more energy-efficient than storage tanks. However, on the other hand, they also cost substantially more to buy and install. Meanwhile, gas tankless water heaters may require modifications to the vent pipe and a larger gas line, while large tankless electric models often draw more electricity than the house can handle.
If you’re looking for the less expensive option, you can purchase a small single use electric unit. It doesn’t take up space as you can mount it under a sink, and it comes in handy if you have a bath or kitchen sink located away from the main hot water heater. Check the recommended flow rate on tankless water heaters before buying the one that meets your needs. While they won’t run out of hot water like traditional storage tanks, tankless systems might not handle multiple users, which causes the water temperature to drop.
Pros & Cons
- It takes up little space and can be mounted either on the inside or outside wall.
- It doesn’t increase installation costs and still meets NAECA standards.
- Causes little to no standby energy loss.
- Up to 30% more energy efficient than comparable storage tank models.
- The size of the unit limits the hot water flow rate.
- Can be expensive to buy and install (house tankless systems cost $600-$1000 plus installation)
- Life expectancy of 20 or more years.
Solar Hot Water Heaters
Even though solar energy is relatively new, it is already being used in hot water heating systems. Install the collector of the solar water heater in a place that receives full sunlight throughout the day. For maximum efficiency, make sure it faces south and is tilted at an angle equal to the latitude. Even though solar water heaters work even at a lower slant or when facing southeast or southwest, they are not as effective.
To move water between the collector and the storage tank, solar hot water heaters use either natural circulation or a pump. While some systems circulate the water from the storage tank through the collector, others use a heat exchanger in the tank to separate the water in the collector from the water in the tank. Though still expensive to purchase and install, solar water heaters are eligible for federal tax credit.
Pros & Cons
- Low to no energy cost.
- The unit pays for itself in savings in 8-12 years.
- For maximum efficiency, the collector must be in full sun year round.
- Expensive to buy and costly to install.
- Usually uses a conventional water heater as a backup system.
- Life expectancy of 20 years.
- Professionally installed systems cost up to $5,000-$7,000.
Hot Water Heater Maintenance Routine
While your water heater does its best to provide you with hot showers, you need to show it some love in return. Following a routine maintenance schedule will keep a hot water tank running for the duration of its expected lifetime and beyond.
- Set the thermostat to 120 degrees. Every 10 degrees you lower the temperature translates in up to 5% savings in energy costs. It also reduces the risk of scalding.
- Maintain 2 feet of clearance around the unit unless the manual states otherwise.
- Remove sediment and debris by drain about a quarter of the tank a few times a year. Turn off the cold water supply, connect a garden hose to the drain valve, then run the water into a bucket until it is clear. If the water keeps its cloudy look, briefly open the water supply valve to stir up remaining sediment. Then drain the tank again. This maintenance practice also keeps the hot water tank quiet during operation.
- Test the temperature-pressure relief valve annually by quickly discharging it twice. Following the testing, monitor the valve for small leaks.
- Examine the sacrificial anode rod every three years by removing the hex head screw. Replace the rod if more than 6 inches of the core steel wire is exposed; the rod is coated with calcium; the rod is less than 1/2 inch thick.
- Improve efficiency by insulating older units with a fiberglass jacket. Be careful to avoid contact with the flue (newer units already are insulated). Also, insulate the hot and cold water pipes.
- When leaving town, use the “vacation” setting on your gas heater’s thermostat. This way, the unit maintains the pilot light without heating the water.