Best Under Sink Water Heaters

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Water heater is a staple for households and you likely hate washing the dishes with the cold water running. Under the sink water heaters give you instant access to warm and hot water when you need to which is one of the biggest advantages to tank heaters. So, If you are looking for a durable water heater for your sink, look no further!

We have compiled three best under the sink water heaters with slightly various features on capacity and strengths. We’ll also discuss the common problems and questions regarding sink water heaters. And then, we’ll tip you on how to find the right under the sink water heaters on your own.

Top 3 Best Under Sink Water Heaters in 2024

1. Bosch Electric Mini-Tank Water Heater Tronic 3000 T 2.5-Gallon

Bosch Electric Mini-Tank Water Heater Tronic 3000 T 2.5-GallonBosch has mini-tank water heaters of various sizes that you can choose from. We are reviewing, in particular, the Tronic 3000 T 2.5-gallon size under sink water heater from Bosch but you can find up to 7-gallon model on Amazon.

Bosch’s Tronic 3000 T can be mounted on a wall or the ground, except for the 7-gallon type. They provide the bracket for shelf or wall-mount. While their sleek and space-saving design means you can fit them inside the cabinet, they won’t be an eyesore if you have to mount it somewhere visible thanks to their sleek design. This water heater is also capable of supplying to up to two different sinks at once.

For the 2.5-gallon and 4-gallon types, they feature a simple 120 VAC plug-in connection (1440 watts). It also uses premium glass-lined material that provides excellent durability for the unit. Also, the unit is insulated with thick CFC-free insulation for the safe and efficient energy consumption of the water heater. There are also several functions you can rely on this sink for.

It can work as your main point delivery water heater where you install the 36-37″ cord plugs into a 120-volt outlet. Alternatively, you can use this to supplement the hot water that flows to your sink to maintain a constant flow of hot/warm water and prevent cold-water sandwiching. It’s also equipped with a temperature-and-pressure relief valve for safety purposes.

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2. Ariston GL4S Electric Mini-Tank Water Heater

Ariston GL4S Electric Mini-Tank Water HeaterHere is another Bosch mini-tank water heater that we are pretty sure will be loved by many. This model comes as a 4-gallon water heater that you can mount on the wall or grounded on the floor. It’s worth noting that this is an upgraded version of the Ariston GL4 and you will soon find out how this model is better than its predecessor.

The GL4S has a temperature adjustment knob that can only be reached if you remove a blue oval cover. Meanwhile, Ariston GL4 has made it easier by placing the temperature adjuster in front of the unit for you to adjust the water temperature between 65-145 Fahrenheit. The upgraded version also has a new sensing probe that improves the temperature regulator and keeps your hot water at a consistent temperature.

Another change that you need to note if you want to buy this to replace your older model is that it’s 13.5” deep while GL4 was 12.25” deep.This model can also work as a complementary heater to your main by providing hot water on instant which removes the lag time.

The great thing about this model is that the installation is as simple as plugging in your TV – all you need to do is plug the water heater to an outlet. No hard wiring required. The voltage measure is 120 volts and requires 1500 watts power to work. It draws only 12.5 amps to heat 4 gallons of water for about an hour.

As it’s a glass-lined tank with superior insulation, the unit is pretty durable and conserves energy by only firing up from time to time to keep the water warm. You will be able to see the neon light lit up when it’s heating and it’s shut off when it’s reached a certain temperature you’ve set. The pressure relief valve is also included.
The water heater also comes with a 1-year warranty on limited parts of the heater. It has a 6-year warranty for the heat exchanger, which means the company is very confident that you are purchasing a durable product.

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3. Ecosmart ECO MINI 2.5-Gallon 120V Electric Mini-Tank Water Heater

Ecosmart ECO MINI 2.5 2.5-Gallon 120V Electric Mini Tank Water HeaterEcosmart’s ECO MINI 2.5-Gallon water heater was included in the list because it’s easy to install, it delivers hot water and it’s durable. The ECO MINI series comes in 4 different sizes from 1, 2.5, 4 to 6-gallon big.

Let’s begin with the installation process. Ecosmart’s 2.5 gallons can be mounted on the wall if you want or simply grounded on the ground. It has a very simple and ‘eco’ design that won’t an eyesore to your kitchen’s interior look. Like Bosch’s Ariston’s, all you need to do is plug it into the nearest standard electrical socket and tap into the water line. They plug into your standard 120 volts and consumes 1440 watts. It draws a total of 12 amps, pretty energy efficient!

There is a pressure relief valve and while the unit comes nicely packed, you might want to get for yourself1/2″ to 1/2″ FIP to MIP brass couplers for extender fittings. The water pipes won’t fit in securely through the steel braided 1/2″ water supply lines.

It has a 1-year warranty on limited parts and a 5-year warranty for leaks.

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Advantages of Under Sink Water Heaters

Under sink water heaters don’t have as much capacity as tank water heaters do. They also consume a high amount of energy in order to get that instant heat for your water. Moreover, they take time to heat up and it depends on the unit itself – older units may begin to take more time to heat up.


But why would you still get point-of-use water heaters? Here are the advantages that other types of water heaters don’t have compared to these instant water heaters.

  • Much quicker than instant water heaters that are not installed under the sink. The reason that anyone chose to put their water heater directly under the sink is to get that 1-2 seconds time lag. Some people think that it’s worth more to install their instant water heater from the source, but the problem with this is that the lag can go from a few seconds to 1-2 minutes! Mini-tank water heaters are even better – you don’t need to wait as they keep a small amount of water warm until your main heater works its magic.
  • Less energy consumption when compared to tank water heaters. You only use the heater when you turn on the sink. Meanwhile, tank-type wastes energy to conserve heat and you waste electricity/gas just to keep your water hot or warm.
  • Constant temperature because don’t you hate it when the water suddenly gets hotter or colder all the time? Under sink water heater provides constant heating to the water right before it’s out of the faucet. Some of these heaters also come with small tanks that allow you to get your hot water right now. Cold-water sandwiching is annoying.
  • Takes less space as you don’t have to keep a tank in your backyard to get constant hot water. They simply take up a small space under your sink or behind your shower. Even the ones with mini-tanks in them don’t take as much space.
  • Unlimited hot water supply because it takes only a few seconds to heat up water as they flow by. Tank water heaters do provide constant hot water but that’s until you run out of it. The recovery rate for these tanks can take a few hours which means, a few hours of cold, freezing water. Meanwhile, mini-tank water heaters provide you instantly the hot water you need while your main water heater heats up water as they pass by.
  • Lasts much longer. Tank water heaters have a lot of maintenance to do if you want to make sure that the gallons of water your household use and consume is safe. As time goes by, rust and other types of contamination may enter your water source, so you will need to clear them out and spend possibly hours to get the tank back to work. Meanwhile, tankless or mini-tank instant water heaters have it much easier with the unit working only when you need them to. The water also doesn’t stay long inside the tank, so there is much less risk of contamination.

Maintenance and Troubleshooting For Under Sink Water Heater

Things To ConsiderSo, even after thorough research and going through thousands of reviews on mini-tank water heaters, it doesn’t mean guarantee your unit will last as long as you thought it would be. Here are some of the most common issues found in mini-tank water heaters and what you can do on your own!

We always highly recommend that everyone check the manual that comes with the unit and follow the installation instructions. Our review sometimes includes tips, such as additional tools that you might need to install them, so do refer to ours before making your purchases. Refer to the manufacturer’s official troubleshooting steps as well before venturing to the unknown territory of DIY repair.

Make sure to disconnect the unit from the electrical socket for safety purposes.

Light indicator

Units like Bosch’s come with light indicators that light up when the heater is on. It will turn off when it’s not, but if you notice that yours do not lit up when you turn the thermostat or for a very long time there are three possibilities: the light is probably busted and you can easily remove the plastic cover with a new one. It can also mean your thermostat is not working or the socket is not working.

  • Unplug and re-plug the unit on a different nearby socket to check if it’s the units or the electrical socket problem.
  • Reset the unit. Bosch has the button behind the cover inside a square housing and you can use a screwdriver to push the button.
  • Take off the unit and flush gently with water for 30 seconds.
  • The thermostat may require replacing after all the other methods did not work.


  • Inspect fittings as even the slightest loose can result in leakages. They may also be corroded and you need to replace them. If it’s the inside that has corroded, replace the whole unit.
  • If the water leaks from the front part of the unit, take it off to see if it’s leaking from the gasket. Replace gasket if that’s the problem.

Recent plumbing works may have caused this as well. Check to see if any back-flow prevention devices have been installed in the water flow from your main heating source or waterline.

Frequently Asked Questions

Frequently Asked Questions

Q1. Do I need to call an expert to install my water heater?

If you want to avoid spending an hour under your sink to hook up your new water heater, sure why not? But the difficulty of installing the point-of-use water heater isn’t that much since these heaters come with installation guides. It requires only common tools and about an hour or so to install the heater and often times, a small unit like this works by being plugged to a standard socket.

Q2. Why do I need a point-of-use water heater in my small house?

As small as your house is and as effective a tank water heater might seem, you will still find a point-of-use water heater to be more useful. First of all, they provide instant hot water to you any time of the day, so you don’t have to suffer from cold water when you wash your dishes. Secondly, your point-of-use water heaters may or may not have a tank and both of them have advantages.

Point-of-use basically ensures that you get your hot water quick or even instant. Mini-tank water heaters do it better and they complement your main heater because it may take time for water to warm up when you’ve just turned it on.

Q3. My point-of-use water heater stops delivering hot water after a few minutes of use. What happened?

Have you checked if your electricity supplies properly to the water heater? If you’ve made sure that you did the installation properly, remember, is it a tank or tankless? Tank water heaters don’t provide unlimited water heater unless you have another main heater working. Tankless water heaters have an endless supply of them because they are instant. But mini-tank models have short recovery time if you run out the tank.

If you wanted something that delivers unlimited hot water, get a tankless, instant water heater that heats up water as they flow. If you hate the 1-2 minutes waiting time to get hot water from your sink, a tank water heater will do the trick for quick use. It can also work as a complement to your main heating source.

Q4. Can the mini-tank water heater be used for more than just one sink?

Yes, typically, these mini-tank water heaters can be used for multiple fixtures, such as the sink and the shower. But note that mini-tank water heaters won’t be able to provide a constant flow of warm water for prolonged use. They work very well, however, to complement your central heating system to get that instant hot water without waiting time.

We’d like to recommend 2.5-4-gallon size for typical household usage. 2.5-gallon is usually great to complement your central heating station as it takes only around an hour to heat back. You might want a bigger size if you’re bringing this for your RV or for shower purposes.

Q5. Do I need to replace the anode rod?

Yes, but the frequency depends on how clean the water that flows through your heater is. Anode rod’s job is to absorb minerals from the water that flows through your heater. The magnesium anode rod with deteriorating over time and when it can’t do its job well, you might notice discoloration or unusual smell from your water.

Some people think it’s suitable to replace the rod every 3-4 years, others recommend at least every 5 years to increase your heater’s lifespan.[/su_spoiler][/su_accordion]


Mini-tank water heaters come in all sizes which make it easy for you to find the right size for your household. Some even come in the size of one-gallon up to 7-gallon which can be installed in RVs or under the sink. Under the sink, water heaters are really great additions to your water supply whether you already have a central heating system or for the main source of hot water.

Installation of these small devices are also easy and mostly, don’t require hard wiring. While they do conserve hot water, the unit only fires up every few minutes to hours which is still better than having a huge tank of water. Point-of-use delivery is also constant and best when coupled with a central heating system to eliminate cold water sandwiching.

If you plan to purchase one, we highly recommend to read our review and check our Frequently Asked Questions section. We also included common troubleshooting tips that even the most inexperienced plumber can do!


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Author - Hans Wimberly
Hans-Wimberly - the owner of Gearsadviser
When I`m not spending time with my beautiful wife and great 3 children, you will find me reloading ammo!
Doing sport shooting, or talking with my friends about (oh, yeah!) guns.

Read more about me here.

At Gearsadviser, I`m committed to ensuring that you have the best possible reloading experience. I conduct thorough research, testing, and evaluation of reloading gear, offering impartial and informative reviews to assist you in making informed purchasing decisions. My reviews are based on hands-on testing, research, and analysis of customer feedback. I regularly update my reviews to reflect changes in product availability and new information, so you can be confident that you're receiving the most current recommendations.

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5 thoughts on “Best Under Sink Water Heaters”

  1. 4 gallons. Seems forgetting that the fresh water coming in to replace the hot water is actually cold. Its not till you flush that cold water through as well dp you start to get hot water from the primary water heater…… Just seems like it would be better to just do a larger tankless under there than the 4 gallon. They are pretty small now days and decently efficient

  2. The remodel I’m doing right now is getting a 9 gal under counter. I’m hoping it is enough to keep my wife happy. No hot water going to the kitchen from the heater, over 40′ away.

  3. A tankless electric water heater gives options for areas needing hot water, but do not have the large hot water tanks near or are unavailable. These devices allow hot water at the location of use. And you won’t waste cold water while waiting for the hot.

  4. When installing, no additional plumbing or venting is necessary, and there’s no carbon monoxide fears.

  5. I used the Eemax Electric tankless water heaters.

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