TOTO's Washlet series has transformed our bathrooms from spaces to relieve ourselves into spaces to relax. The line, launched in 1980, has brought innovation to Japan's "toilet culture." For the last 30 years, Washlet products have continued to evolve as TOTO incorporates the latest human- and environment-friendly functions.
In this first TOTO Green Story, we tell you the story behind the development of the fast-heating toilet seat, which automatically conserves energy.
Hironobu Hattori
Product Development Section No. 1, Washlet Development Department No. 2
Hattori worked on the development of the materials and structure of the fast-seating toilet seat.
A family of four spends an average of around 50 minutes total on the toilet each day. It is obviously a waste of energy to keep warming the toilet seat for the remaining 23 hours and 10 minutes. However, a cold toilet seat is what the Japanese hate more than anything else, given the lack of central heating in Japan. So, I thought there may be a way to instantaneously heat the toilet seat only when someone is seated on it, and began innovating the materials and structure of the seat.
It takes about 6 seconds for a person to sit down on the toilet, and the optimum temperature to feel that the seat is "not cold" is 29℃ and warmer. So, our goal was to create a system that would heat the seat to 29℃ in 6 seconds.
To heat the seat that quickly, we needed to make it thinner, but to maintain sufficient strength. We struggled to find a fair trade-off between warmth and strength. In the end, we decided to use fiber reinforced plastic (FRP), reduced the thickness from 3 mm to 1 mm, and made it double-layered with a glass-reinforced fiber composite lining. For about 2 years, we worked on prototypes while constantly checking the measuring instruments.
We also improved the pattern of the heating coil installed on the back of the Washlet. By making the heating coil thinner and longer to completely cover the parts that should be heated, we devised a way to make it energy efficient. For this purpose, we researched the parts that directly touch the seat by asking staff members to powder their buttocks and sit on the seat. The plumpness of the buttocks varies among individuals, as do the resulting "buttocks lines." Men and women also sit in different positions on the seat. I didn't realize this until female staff complained that they had felt the cold front part of the seat. When examining the "buttock lines" only with male staff, we didn't notice this.
We finally completed the fast-heating toilet seat. It was the first time in the 30-year history of the Washlet that we had changed the materials and structure. The combination of the dual heat-retention function achieved by the insulation incorporated in the toilet cover and the fast-heating toilet seat has drastically improved energy efficiency, which I made every effort to achieve without compromise. I think that the fast-heating toilet seat is a big step forward in the Washlet's history. I hope to make it the standard for TOTO's entire Washlet line.
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