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Serving The Greater Fresno Area Since 1970

Serving The Greater Fresno Area Since 1970


Donald P. Dick Air Conditioning Blog

Why Is My On Demand Water Heater Slow to Heat Water?

Why Is My On Demand Water Heater Slow to Heat Water?If you’ve installed a new on demand water heater, also known as a tankless water heater, but aren’t receiving your hot water as quickly as you expected, you’re not alone. Many homeowners are surprised when their new tankless water heater doesn’t turn out to be the perfect solution they dreamed about. While there are lots of benefits to tankless water heaters, they do have some drawbacks, and a bit slower access to hot water can be one of them. 

Flow Rate

While on demand heaters don’t have a limited capacity, they do have a limited flow rate. This means your unit can only raise the temperature for a limited amount of water going through the pipes at a time. If you have a dishwasher, washing machine and bath tub all operating at once, your tankless heater may not be able to produce hot water for all devices simultaneously. Using more than one outlet for hot water at a time can slow things down significantly. Also, it’s probable that an electric on demand water heater is slower than its gas-fueled counterparts.

Other Considerations

Other factors may explain why your on demand water heater is slower than you expected. Unless your unit is close to the water-using outlet or appliance you’re using, the cold water in the pipes needs to be expelled before hot water can be pumped through. The farther away from the heater you are, the longer this can take. Certain types of tankless water heaters may not be adequate for your temperature needs, so make sure you buy a unit with enough temperature rise before an installation. Also, be aware that you have the option of purchasing a whole-house tankless unit, along with one or more smaller, point-of-use on demand heaters to be installed at far-away water outlets or major hot water guzzlers.

If you’re still not satisfied with the performance of your water heater, you may want to hire a reputable HVAC professional to make some adjustments. To receive more information about your water heater or other topics related to the comfort of your home, please contact us at Donald P. Dick Air Conditioning. We provide quality HVAC services to the Fresno area.

Our goal is to help educate our customers in the greater Fresno, California area about energy and home comfort issues (specific to HVAC systems). For more information about water heaters and other HVAC topics, download our free Home Comfort Resource guide.

Credit/Copyright Attribution: “David-Koscheck/Shutterstock”

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