This is the proof of "Genuine onsen" you can see this at indoor's bath floor made by 20years of history. It means that the spring source that comes from earth is not diluted, (additive free) or boiled (no heat added), and its water is directly conducted to the bathtub without putting into a tank;it means pouring off all the overrun water. This is what is called a "Ｇｅｎｕｉｎｅ onsen". Onsen Spas that do not have a storage tank and conducts the water directly to the bathtub from the spring source is said to "have scarcity value". The hot water of Hoheikyo Onsen is the only spa in Sapporo city that does not use a storage tank. It pumps up the hot spring directly to the bathtub.Therefore, the hot spring does not get exposed to the air at all. ..the water that goes through a circulation device with a filter and it is reused many times.The hot spring that is put back to the bathtub has many bacteria like the legionella bacteria which are very easy to propagate;therefore,chlorine is used to its elimination. Chlorine is a very strong sterilizer,and for that reason it ends up breaking down our skin cells,becoming one of the reasons of aging. When exposed to chlorine the skin becomes more sensible to the action of ultraviolet rays which makes the skin more prompt to have one of the biggest enemies of women: fleck and freckles.Not only had that,but specially people that have atopic dermatitis (growing in number in recent years) had to be more cautious.Also there is a risk of producing a carcinogenic substance called THM (trihalomethane) when combined to other substances in the water.