Instant Heating Bidets vs Water Tank Heating Bidets: What's the difference?

On your adventure of choosing the perfect bidet for your home, you most likely have come across bidets that uses water tank heating technology, but maybe you came across instant water heating bidets as well. What do these technologies do, and which one's the best? Read on to find out.



Water Tank Heating

Most bidets are able to provide heated water with an internal water tank heating system. How it works is that the bidet draws in cold water diverted from the T-valve attached to your water shut off (basically, the water that goes into your toilet tank). The water then goes inside a built in water tank inside the bidet. The water tank has a temperature sensor and a heater, and can heat up the water to a specified temperature, and constantly turns the heater on and off to keep the water exactly at the specified temperature. Once you sit on the bidet and go to use the water, the warm water from the tank is immediately available for use. Sometimes you'll have residual water in internal water tubing / nozzle from the last use, and that residual room temperature water will shoot out first before the warm water from the tank shoots out. That sometimes explains why some people feel a colder spray for maybe 1 second, before the warmer water comes out. The water tank can usually hold about 750 mL to 1000 mL of water, which is enough for one wash cycle. As the water is being used and depleted from the water tank, the tank is refilled with the cold water fresh from the plumbing. This cold water mixes with the already warm water inside, and cools the water. But, the heater of the tank will still be at full blast, heating the water. This is sometimes called a "hybrid heating technology". The result would be a spray that starts off warm for the first 30 seconds or so, and there will be a small but noticeable gradual cooling off of the water as the spray cycle nears completion. The advantage of a water tank heating system is that it's cheaper to implement, so you will find this on 90% of all bidets. Another advantage is that the water will always come out exactly at the temperature you set it at. Most bidets have choices that range from 30°C to 40°C. The disadvantage would be the slightly higher energy use compared to an instant heating system, and the gradual temperature drop over the spray cycle. In general, the energy cost for keeping the water tank heated is just a couple of cents a day; it's not an energy intensive process.




Instant Water Heating

A newer technology that emerged in the last 5 years or so is an "instant heating system". How it works is that it has an extremely powerful heating core that can instantly heat up the incoming room temperature water to whatever temperature you set the bidet to. Because it doesn't have a water tank, instant heating bidets are significantly thinner than their water tank bidet counterparts, sometimes up to 35-40% thinner. And because it doesn't rely on a preheated water supply, and instead can instantly generate a warm stream of water, the bidet can technically provide an infinite supply of warm water without having any noticeable temperature decrease like you would with tank based bidet seats. The only disadvantage from this type of bidet is if the incoming water is very cold, at temperatures of 5°C degrees or below, sometimes the instant heating cores won't be able to heat up the water to the maximum available temperature. Instead, the heater will heat the water to a few degrees below that temperature, because the heater can only increase the water temperature by so much. For example, let's say that a bidet can set the water temperature to a

maximum of 40°C, and the heater can increase the water temperature by +33°C. If the incoming water temperature is 10°C, then the heater will have no problem heating up the water to the specified 40°C. However, if the incoming water temperature is 3°C, then the heater will heat the water to a maximum temperature of 36°C (3°C + 33°C). However, this is mostly a none issue, because it is difficult to detect a temperature change of just a couple of degrees, and usually incoming water in a household is higher than 10°C, because the water would have been sitting inside the pipes that are inside your house, achieving the ambient temperature of your house. However, if the water going to your toilet is coming from straight outside and it's only 1 or 2°C above freezing, AND if you want to use the warmest settings for the water spray, then you might want to check out a water tank heating bidet instead.




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