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This size is the smallest size water heater that is not designed to be a point of use water heater for a single fixture. A 30 gallon water heater should be able to supply enough hot water to meet the needs of a household of 1 -2 people with only one bathroom. A good way of measuring your hot water requirements is calculate your peak hot water usage and compare it the first hour rating of a water heater. To calculate your peak hot water usage, fill out the peak usage worksheet found here. The first hour rating is a measurement of how much hot water you can get out of your water heater in its first hour of operation (starting with a full tank of hot water). The first hour rating on 30 gallon tanks is between 42 and 53 gallons so they are limited to one bedroom and one bathroom applications.

Upsizing or Downsizing

Many times when someone finds out what size water heater they have they think about upsizing or downsizing their water heater. If you are thinking about downsizing your water heater, keep in mind that this is not always possible. Plumbing code requires that you keep at least a minimum first hour rating on the water heater that is in your home. The minimum rating on your water heater is determined by the number of bathrooms and bedrooms in your home. You can reference the chart below to see what the minimum for your home.

Water Heater 1st Hour Rating

Sometimes people also want to be able to get more hot water out of their water heater. To accomplish this, they want to upsize their water heater. If your previous water heater met the code requirements there isn’t usually an issue with upsizing your water heater from a code perspective. However, you may still run into some difficulties upsizing your water heater. The first consideration is space. Water heaters with more water in them are typically wider than your current heater. Do you have room for this? Secondly, when you are upsizing your water heater, it will typically have a larger BTU (British Thermal Units) rating on the water heater. The larger BTU rating may require a larger vent. Re-doing your venting can be an expensive proposition, check with your installation coordinator to see if this will be necessary.


If you have questions about 30 Gallon water heaters, need service/repair/installation, please do not hesitate to contact us via phone or the below form!