I came across an interesting article online about adding hot water to the bath. So, I would like to summarize and share some of the interesting points here. In Japan, we have a custom of lying and soaking in the bath . However, the article said there are some habits to avoid when adding more hot water. One should be especially careful during the winter and also those that might affect one's hygiene. The habits to refrain from are as follows 1)To add more hot water again the following day Some people might reuse the water which was used in the bath the day before to save utilities. Actually, that isn't recommended from a hygienic perspective because skin oil and sweat are left in the bath and their bacteria grow more and more as time goes by. You can't get rid of them completely even though the water looks clean. So, you should replace the bath water every day. 2)To add more hot water to one with a bath bomb. If the parts of the bath bomb are stuck on the inside of the pipe, it can damage the metal parts and cause sensor malfunctions. On the other hand, some bath bombs are not affected by reheating the bath water. That's why you need to check if they are available. 3)Very little hot water when reheating the bath. Sometimes the reheating function doesn't work when there is very little hot water. So, you need to increase the volume of hot water in the tank/geyser ?when you reheat the bath. I sometimes reheat the bath water when I get home late due to working overtime. So, this information is very useful for me.