The most common reason for an increase in a utility bill is an increase in water consumption.  The causes for an increase in water consumption are many and varied and we cannot usually determine the exact reason for the increase.  The first step is to make sure that your property does not have a plumbing problem such as a leaky toilet or faucet, or a broken pipe.  The vast majority of high water bills are due to such a problem.  Also, be aware that summer-time watering can cause very drastic changes in your water/sewer bills.  If you are unable to find an explanation for your high water/sewer consumption, you may request, in writing, an investigation by the Water/Sewer Department by writing to the Water Superintendent at PO Box 1230, Bozeman, Mt. 59771.