Is it permissible to perform Tayammum at work or during travel if water is ten or fifteen minutes away, or must one wait until reaching the water?

A distance of ten to fifteen minutes is considered close by custom. One must go to the water and perform ablution (Wudu') from it, or ritual bathing (Ghusl) if there is a state of Janabah (major ritual impurity). Tayammum (dry ablution) is not permissible in this case due to the absence of a valid excuse.