Water Heaters of Ancient Civilisations

Throughout history, ancient civilisations have developed innovative methods to heat water. They used hot water for bathing, cooking, and maintaining comfort in their homes. This article delves into the water heating systems of five ancient civilisations.

1. Ancient Greece: Kaminos (c. 2500 BCE)

The kaminos, a Greek hearth, was a central fixture in ancient Greek homes. It was a simple, open fireplace where families gathered for warmth, cooking, and heating water.

The kaminos consisted of a circular, shallow pit dug into the ground lined with stones or clay. Water was heated in large pots or cauldrons placed over the open flame, providing hot water for bathing and other household needs.

Burning charcoal

2. Ancient Rome: Hypocaust (c. 500 BCE)

The hypocaust showcased the remarkable engineering capabilities of the Romans.

Used in public baths and the homes of wealthy citizens, the hypocaust circulated hot air. The system heated floors and hollow walls to warm the rooms above.

Large boilers heated the water and piped it into the baths. This sophisticated system highlights the importance of relaxation and cleanliness in Roman culture.

Ancient Rome Hypocaust

3. Ancient Persia: Korsi (c. 400 BCE)

The korsi was a traditional Persian heating system used to warm living spaces and heat water. It consisted of a low, wooden table covered with a large quilt or blanket, and a charcoal brazier.

The heat from the brazier would warm the area beneath the quilt, creating a cosy space for family members to gather.

Water was heated in pots or kettles placed over the brazier. It allowed the Persians to get hot water for various household tasks.

Delicious food

4. Ancient China: Shui Lu (水炉) (c. 200 BCE)

The shui lu, or water stove (水炉), was common in ancient Chinese homes. It was a large brick or stone structure with several compartments built to heat and cook food.

The shui lu used a single fire to heat several pots of water simultaneously. This efficient design allowed families to conserve fuel. It also helped maintain a constant hot water supply for different activities.

Ancient China: Shui Lu (水炉) (c. 200 BCE)

5. Ancient Japan: Onsen (c. 700 CE)

Ancient Japan’s onsen or hot spring has been integral to Japanese culture for over a thousand years. Onsens were These natural springs, heated by geothermal energy. They were revered for their healing properties and social significance.

Early onsens comprised simple, open-air pools where people could bathe and relax. Over time, more elaborate bath houses were built around the hot springs. They provided a communal space for relaxation, rejuvenation, and social interaction.

Hot Spring from Japan

Downsides of ancient water heaters

The water heating systems of ancient civilisations were ahead of their time. But they had certain drawbacks.

Lack of privacy

One of the most significant downsides was the lack of privacy associated with public bathing systems. For example, the Roman baths and Japanese onsens were communal spaces. This meant individuals often had to share these facilities with others.

In some cases, this could lead to overcrowding and limited access to hot water.

Low frequency of use

Another issue with ancient water heaters was their low frequency of use. Compared to modern water heating systems old systems were often only available at specific times or locations.

People often had to travel long distances to access public baths. This limited their use of hot water. It was also problematic in harsh weather, as reaching the bath houses could be dangerous.


Ancient water heaters were not always reliable in providing hot water. Many relied on natural resources, such as wood or coal, for fuel. These resources could be scarce or expensive. Sudden weather changes like a cold snap or a heat wave could also affect the availability of hot water and the cost of producing it. Hot water was at best, inconsistent and unpredictable.

The technology used in olden times were inefficient and often broke down. Ancient water heaters are certainly not as dependable as modern heaters. Today, we take consistent, instant hot water for granted.

Modern heaters today

Thanks to technological advancements, modern heaters have made our access and use of hot water convenient.

Here are some of the benefits we are blessed with today, that we would not have if we were born centuries ago:

Speed heating

Speed heating is one significant benefit of modern water heaters. It ensures hot water is readily available whenever it is needed. People didn’t need to wait long, unlike in the past.

The instant availability of hot water also saves time and reduces energy consumption.

MAX Heating Technology

AOS Bath’s MAX technology is a hot water multiplier feature. This increases the amount of hot water available to you without changing the heater’s capacity.

Everyone in the family can enjoy a constant supply of hot water, even during peak usage periods. No longer will you run short or have to wait too long for water to heat up.

Renewable Energy Heat Pumps

Heat pumps are another significant advancement in modern water heating. These heaters use ambient air to generate heat. They require less energy than traditional electric or gas-powered heaters. Households can reduce their carbon footprint while enjoying the convenience of hot water.


Ancient water heaters showcased the resourcefulness and ingenuity of our ancestors. While these systems had limitations, they laid the foundation for today’s modern and convenient heaters. We sure are lucky to be born in this age of modern conveniences.


How effective were ancient water heaters?

While ancient heaters were effective for their time, they were much less efficient than modern systems. Today, we can harness the power of renewable energy and clean energy to provide hot water.

Ancient heaters were widely used and safe, but hot water was more for public use than private use.

Digital heaters are sought after for their high performance while heat pumps are the most consistent renewable energy heaters in Singapore.

AOS Bath Team

AOS Bath Team