What to Look for when Buying an Under Sink Water Heater

water heater under kitchen sink

Not many people pay attention to their under sink water heater. Until it breaks, that is. When it is time to replace your under-the-sink water heater, there are a few things to consider.


The most obvious consideration has got to be the size of it. If you have very little space, you are going to need a tiny water heater. Since you will not have space for a storage tank, tank-less water heaters are ideal for underneath sinks.

Gas-Type vs Electrical

Since the water heater will be located under your sink, the ventilation needed to vent a gas-type water heater properly is impossible. You will need only to consider electrical models.


Another important aspect is the amount of electricity the water heater will require to work. Will your circuit breaker be able to support the electrical demands? It is best to hook your water heater up to its own circuit.

Water Demands

Do you have a dishwasher that is going to be utilizing the water heated by this device? Or is it merely to heat the water for the sink?

A dishwasher demands 1 to 3 gallons of water per minute, while a kitchen sink demands 1 to 1.5. Tankless water heaters generate a temperature based on the flow rate demand, thus making it an important time to decide if you are going to install that dishwasher you have always dreamed of or not.

Incoming Water Temperature

If you live in Alaska, the incoming water temperature will be significantly lower than in Florida. You will need to determine how much you need the temperature of the water to rise to reach your desired temperature. If the temperature of the ambient incoming water is only 50 degrees and you require a minimum of 140 degrees for dishwasher disinfection, you will need a tankless water heater that produces a 90-degree temperature rise at 3 gallons per minute.

However, if you anticipate additional usage, it is important to calculate the rise in temperature for the maximum number of gallons per minute you think might be used.

Installation and Maintenance

Proper installation will play a vital role in getting maximum energy efficiency. Installation should be done by a qualified, licensed plumbing and heating contractor.

As with most electrical appliances, you will need regular care and maintenance to get the most life out of it. Follow the guidelines that are found in the owner’s manual.

Life Expectancy

Most tankless water heaters have a minimum life expectancy of 20 years. However, some parts may burn up before then and need replacing or repair. Thus, if you notice significantly lower performance, there is a good chance it requires a minor repair.