The Problem that often occurred in PDAM Kabupaten Semarang branch Ungaran is the lateness in payment water bills. More than 1000 customers are lateness to pay each month. This study aims to determine the relation of customer classes in PDAM of the lateness in the payment of water bills and determine customer behavior patterns associated with the lateness in the payment of water bills. The method used is the chi-square and descriptive statistics. The results using the chi-square method showed there is a relation between classes of customers to lateness payment of water bills customers. The calculation of descriptive statistics using SPSS version 17, as many as 56% of respondents said that income does not meet their daily needs. As much as 66% of respondents said that income received each month is uncertain. As many as 66% of respondents said that the timing of receipt of monthly income does not match the specified time. Terms of payment point, 66% of respondents stated that the water bill payment locations away with a residence. While psychological terms, 44% of customers state that does not have time to pay on time. So the conclusion is the income becomes a major factor affecting in the payment of water bills, then the other factor payment locations away from residential customers and no time to pay water bills result in customers not paying on time