how does a boiling water tap work

Having boiling water available all the time sounds like a great idea. Imagine never having to wait for the kettle again!

But how does a boiling water tap work? As we answer the question, we’ll see that they have an electric-powered heater and tank to heat and store water below your kitchen sink at the required temperature, ready for use.

An instant hot water tap can dispense boiling water instantly, so hot drinks or instant foods are much quicker to prepare. They can even actually save you money with their superior energy efficiency.

What Is a Boiling Water Tap?

A boiling water tap can be a separate, extra tap or a multifunction one that replaces your regular tap.

Whichever option you choose, the boiling water tap gives you, in addition to your regular hot and cold water, boiling water on demand.

multifunction kitchen faucet

Some designs can even provide filtered cold drinking water as well.

What Are the Advantages of a Boiling Water Tap?

So why might you want a boiling water tap in your kitchen? Let’s take a look at the reasons why many people are adding them to their homes.

Save Time for Hot Drinks

The most apparent advantage of an instant hot water tap is saving time by never having to wait for the kettle to boil again when you want a cup of tea. The water is always there, ready and waiting for you.

Cook Quickly

If you need to boil some food, the water is ready for you. You won’t need to wait for the saucepan to boil to cook vegetables or pasta. If you’re a fan of instant pot noodles, they really can be available in a flash now.

Easy to Use

If you can turn on the hot water tap, you can use a boiling water tap. Some people have difficulties lifting the weight of a kettle and find getting water from a tap requires much less effort.


It’s common to fill your kettle up with more water than you need, leading to water waste. The boiling water tap dispenses just what you need. No more, no less.

Energy Efficient

The typical instant hot water system will use less energy because you’re not boiling water unnecessarily.

Makes Washing Up Easier

Having boiling water available at your sink can make cleaning burnt-on grease and grime from your pans and cooking trays considerably less effort.

More Water Available

If you want to fill up a thermos flask or need a lot of water for cooking, you might need to boil an average kettle several times to get enough. Boiling water taps can have large tanks with all the boiling water you need.

Filtered Water

As a bonus, most boiling water taps come with a water filter to purify your water and, in particular, reduce limescale in a hard water area.

How Do Boiling Water Taps Work?

We’ve considered what they are and what they can do for you, so let’s address our initial question: how does a boiling water tap work?

Boiling water taps work from a sealed storage tank located under your sink and connected to your cold water supply. This water tank has an electrical immersion heater inside to heat the water to near boiling point. A thermostat makes sure that the water is always at the right temperature, ready for when you need it.

There are usually controls to adjust the water temperature that comes from the tap. Many instant hot water taps supply the water a few degrees below boiling, but this is more than hot enough for tea, coffee or filling cooking pans.

Some boiling water taps have pressurised tanks with a small drain pipe to let out steam as required. Others use a tap design that can vent when needed.

What Different Types of Boiling Water Taps Are There?

There are several different designs of instant hot water taps available. The right one for you may depend on several factors.

Boiling Water Only Taps

This type will be particularly helpful if you need boiling water only. Maybe you want to have a drink making area in an office or would like to add boiling water from a single tap on a kitchen island away from your main kitchen tap.

You can think of this kind as a kettle tap. All it does is supply near-boiling water.

3-in-1 Taps

A 3-in-1 tap adds a boiling water supply to your regular hot and cold tap water options.

These are the most commonly chosen and are the easiest to retrofit as they can usually just replace your regular tap.

stylish kitchen sink and fixtures

4-in-1 Taps

A 4-in-1 tap adds cold filtered water to your choices of boiling, hot and cold water. Many people choose these taps to gain an unlimited supply of filtered drinking water. Water filters have the benefit of reducing space in the refrigerator and saving money by your no longer having to buy bottles of water or using a filter jug.

How Safe Are Boiling Water Taps?

A lot of people ask how safe boiling water taps are. After all, having a constantly available supply of boiling hot water at your taps might sound dangerous, especially if you have young children.

Fortunately, the manufacturers have designed safety features, including a child lock into these taps, to reduce the risk of accidents. 

All boiling water taps have a spring-loaded safety button or safety catch to prevent boiling water from coming out accidentally or left flowing uncontrolled. The button or catch needs to be pressed and kept pressed while you open the hot water tap for the water to flow. As soon as you release the button, the hot water will stop.

Additionally, the water pressure of the boiling outlet is much lower than a regular water supply to remove the danger of getting scalded by splashes from an unexpectedly fast flow.

The metalwork on the tap has large amounts of insulation, so it doesn’t get dangerously hot and risk burning you. Most kettles, in contrast, get very hot on the outside and can easily cause burns.

Finally, unlike kettles, instant hot water taps are fixed. They can’t be moved and can’t be accidentally knocked over.

Are Boiling Water Taps Expensive to Run?

Although they are relatively expensive to buy initially, an instant boiling water tap shouldn’t cost any more to run than a kettle if you use a reasonable amount of hot water. Because you only use the exact amount of hot water you require rather than heating a kettle full unnecessarily, you may have less wasted energy.

It would be best if you remembered to factor in the cost of replacing the limescale filter system, although this is usually only needed once every six months.

Choosing the Best Boiling Water System

If you’ve decided that you want an instant hot water tap in your home, there are a few things you need to take into account.

  • Tank Size – Different systems come with different sizes of water tanks. You’ll want to make sure you have a tank large enough for your needs while not so big that you’re heating water unnecessarily. Bigger tanks also take up more space underneath your sink, so make sure you have enough space for the tank you’re considering.
  • Temperature Controls  Not all systems have an adjustable temperature on the boiler unit tank. You might be OK with a set temperature or could find the ability to change the temperature quite useful.
  • Filtered Cold Water – If you drink a lot of bottled water, selecting one with a filter system may be a convenient solution.

What’s the Difference Between Boiling Water Taps and Instant Hot Water Taps? 

The simple difference is that a true instant boiling water taps deliver water at just below 100°C. An instant hot water tap will produce very hot water that can vary between 80°C – 98°C.

The right one for you will depend on what you want to use it for. It’s also worth knowing that you can turn down most true boiling water systems to produce a lower temperature.

While you should usually make tea with near-boiling water, if you drink a lot of coffee, you may want a lower water temperature as coffee beans can easily get burnt, which affects the taste.

It’s worth knowing that, generally, instant hot water taps will be cheaper to buy than those that make truly boiling water.

Are Boiling Water Taps Worth the Investment?

Looking at the question of “How does a boiling water tap work?” we’ve seen that these convenient appliances can provide instant hot water at very high temperatures, which you can use for hot drinks or cooking.

By having a small boiler tank underneath your sink to heat water, you can replace your traditional tap with one that can have boiling water in addition to your usual hot and cold taps.

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