How do under counter water heaters work?

Under counter water heaters are compact and efficient water heating systems that are designed to be installed under sinks, counters, and other concealed spaces. They provide hot water on demand without taking up much space, making them ideal for use in apartments, condos, office kitchenettes, wet bars, and other small living areas.

What are the different types of under counter water heaters?

There are three main types of under counter water heaters:

• Electric under counter water heaters
• Gas under counter water heaters
• Tankless under counter water heaters

Electric Under Counter Water Heaters

Electric under counter water heaters work just like regular household water heaters. They consist of an insulated storage tank that keeps water hot and ready for use. The water is heated by electric heating elements submerged in the tank. Electric under counter heaters are available in storage tank capacities ranging from 2-10 gallons.

Gas Under Counter Water Heaters

Gas under counter water heaters also utilize a storage tank, but use a gas burner to heat the water instead of electric elements. The gas burner ignites as necessary to maintain the temperature set point. Gas models provide faster water heating than electric, but require proper ventilation for exhaust gases.

Tankless Under Counter Water Heaters

Tankless under counter water heaters work on demand without a storage tank. They consist of a gas burner or electric heating element that only activates when hot water is needed. Cold water travels through a heat exchanger, getting heated instantly. Tankless heaters provide a limitless supply of hot water but have a slightly lower flow rate.

How does an under counter water heater work?

While under counter water heaters come in different designs, their basic operation is quite straightforward:

1. Cold water enters the heater through an inlet pipe.
2. In storage tank models, the water is warmed and stored in an insulated tank.
3. In tankless models, the water flows through a heat exchanger and is warmed on demand.
4. When a hot water tap is opened, the heated water exits the heater through an outlet pipe.
5. A thermostat or sensors modulate the heat source to maintain the desired water temperature.
6. As hot water is drawn, incoming cold water refills the tank or heat exchanger, allowing the heating cycle to continue.

Key Components of Under Counter Water Heaters

Under counter water heaters include several key components:

• Storage tank or heat exchanger – Stores hot water or instantly heats it
• Heating element or burner – Provides heat for water heating
• Thermostat – Maintains optimal water temperature
• Insulation – Retains heat and improves efficiency
• Temperature and pressure relief valve – Releases excess pressure
• Anode rod (in tank models) – Protects against corrosion

What are the benefits of under counter water heaters?

Under counter water heaters offer several advantages over conventional water heating systems:

• Compact size – Fits easily under counters and in small spaces
• Local hot water source – Provides hot water at the point of use, saving water
• Simple installation – Can reuse existing water lines
• Lower operating costs – Requires less energy to heat small volumes
• Endless hot water (tankless models) – Offers continuous on demand hot water
• Lower purchase price – Costs considerably less than whole house systems

What are typical under counter water heater capacities?

Under counter water heaters are available in a range of storage tank capacities:

Capacity	Typical Use
2 gallons	Wet bar or prep sink
4-6 gallons	Small apartment kitchen
10 gallons	Large kitchen sink

Tankless models do not store hot water – they provide endless hot water on demand within their maximum flow rate.

How much under counter hot water is needed?

Choosing the right size under counter heater depends on your expected hot water demand. Some typical uses and requirements include:

• Hand washing – 2-3 gallons per use
• Kitchen sink – 4-8 gallons for washing dishes
• Bathroom sink – 4-6 gallons
• Shower – 2 gallons per minute of flow
• Bath tub – 20-30 gallons

For a kitchen sink, an under counter unit with 4-6 gallon capacity is usually sufficient. For a bathroom vanity sink or small shower application, a 2.5-4 gallon model will work well. Know your fixture flow rates and add up your expected hot water needs.

What size under counter water heater do I need?

Use this table as a general guide on sizing an under counter water heater for your application:

Application	Recommended Capacity
Wet bar, prep sink	2-3 gallons
Bathroom vanity	2.5-4 gallons
Kitchen sink	4-6 gallons
Small shower	4 gallons
Double bowl kitchen sink	6-10 gallons

For tankless heaters, size based on the maximum required flow rate in gallons per minute (GPM).

How are under counter water heaters installed?

Under counter water heaters are installed using the following steps:

1. Select an under counter location like a large cabinet or closet.
2. Turn off water supply and drain plumbing lines.
3. Cut into the cold and hot water lines and install T-fittings.
4. Connect heater inlet and outlet to T-fittings.
5. Run electrical or gas supply line if needed.
6. Anchor the heater securely in place.
7. Connect a discharge pipe to the T&P valve.
8. Turn on water supply and check for leaks.
9. Flush the tank or heat exchanger if necessary.
10. Enable power/gas supply and verify proper operation.

Consult the manufacturer instructions for full installation details. In some cases, professional installation may be recommended.

Installation Considerations

• Location should be close to fixtures, protected from freezing
• Under counter heaters require proper clearance and ventilation
• Discharge T&P valve appropriately based on codes
• Size lines and fittings to minimize pressure drop
• Install sediment filters if water quality is poor

How much does it cost to install an under counter water heater?

Installing an under counter water heater costs $200 to $600 as a rough estimate, with the average homeowner paying around $400. This covers common costs including:

Cost
Under counter water heater unit – $150 to $500 depending on type and capacity
Plumbing parts – $50 – $100
Electrical or gas line materials if needed – $20 – $50
Labor, if hired – $150 – $200
Total average cost – $400

Hiring a professional plumber typically adds $150-$300 to the total cost. Homeowners with some DIY plumbing experience can install their own for much less.

What’s the best under counter water heater brand?

The most highly recommended under counter water heater brands include:

• Rheem – Best overall reputation for performance and reliability
• A.O. Smith – Top brand among plumbers and contractors
• Bradford White – Excellent customer support and warranties
• Rinnai – Leading brand for tankless units
• Bosch – Known for quiet operation and efficiency

When choosing a brand, look for units certified by AHRI and energy rated by EF or UEF. Also check warranties and after-sales support.

Under Counter Water Heater Reliability Ratings

Brand	Reliability Rating
Rheem	4.7 / 5
A.O Smith	4.5 / 5
Bradford White	4.4 / 5
Rinnai	4.6 / 5
Bosch	4.3 / 5

Rheem emerges as the most reliable brand according to contractors and consumer reviews.

How much electricity does an under counter water heater use?

The electricity usage of an under counter electric water heater depends on the tank size, insulation, and thermostat setting. Some approximate electricity costs for common models are:

• 2 gallon – 150 kWh per month, $15 – $20 in electric costs
• 4 gallon – 190 kWh per month, $20 – $25 monthly
• 6 gallon – 220 kWh per month, $25 – $30 monthly
• 10 gallon – 350 kWh per month, $35 – $45 monthly

To maximize efficiency and savings:

• Set temperature to 120°F or less
• Insulate hot water pipes
• Use low flow fixtures
• Choose ENERGY STAR certified model

How to maintain and increase the lifespan of under counter water heaters

Under counter water heaters can last 5-10 years with proper maintenance. Follow these tips:

• Drain and flush tank annually to remove sediment
• Inspect anode rod and replace if deteriorated
• Check T&P valve by manually opening once a year
• Keep water heater free of dust and debris
• Avoid hard water if possible; install filters as needed
• Maintain water pressure below 80 psi
• Keep electrical connections dry and intact
• Check for leaks and unusual sounds

Replacing the anode rod every 2-4 years greatly extends the tank lifespan. Also lower the temperature setting to 120°F. Following the manufacturer maintenance schedule will maximize the heater’s longevity.

Troubleshooting common under counter water heater problems

Some typical issues with under counter water heaters include:

Not Enough Hot Water

• Heater undersized for demand
• High demand periods
• Thermostat set too low
• Element or gas burner issue
• Sediment buildup

Water Not Hot Enough

• Thermostat set too low
• Scale reducing heat transfer
• Bad heating element or gas control
• Dip tube issue

Leakage

• Corroded tank
• Damaged fittings or pipes
• Failing T&P valve
• Improper installation

Noisy Operation

• Sediment buildup
• Water hammer
• Loose parts
• High water pressure

Consult a professional plumber for repairs. Prevent issues with regular maintenance and replacing older units.

Conclusion

Under counter water heaters provide an efficient way to get hot water where you need it without taking up much space. Models with storage tanks from 2-10 gallons can be conveniently installed under counters. Tankless heaters also give you limitless hot water on demand. When properly sized and maintained, under counter heaters work well for sinks, wet bars, and small bathroom applications, saving energy and water. Choose a top brand like Rheem and install properly to get the best performance. With periodic maintenance, an under counter water heater can provide many years of hot water.