Fugaku

Spring-source temperature

55.6°C in the inn's source data; the page also lists a maximum of 84°C

Bathing temperature

Not published as a fixed temperature for the public baths

Spring source

Centrally managed Gero Onsen water, supplied from the Gero Onsen cooperative's tank through a dedicated pipe

Spring classification

Alkaline simple spring

pH

9.1

Flow rate

1,250 L/min for the centrally supplied Gero Onsen system, not Fugaku's individual spring output

Water handling

The public baths use a partial discharge-and-recirculation system, with some heating to maintain temperature and chlorine-based sanitation. The inn describes the private bath as free-flowing, but does not publish a complete bath-by-bath treatment table for it. The hinoki bath in the panoramic suite is explicitly not a natural hot spring.

Tattoos are not permitted in the public baths or outdoor baths; the private-bath rule is unconfirmed. The private bath is reservation-only for 45 minutes between 15:00 and 22:00, once per group. The bath on the fifth floor and the basement bath are connected by stairs, with no elevator. The suite's hinoki bath is not an onsen.