A glass of tap water in your house may cost more than the same glass in a house just a few miles away.

A new report by Citizens Campaign for the Environment says the cost of bringing water into homes on Long Island varies greatly among the 48 different water districts serving Nassau and Suffolk.

Customers of the only privately owned Long Island water provider, New York American Water in Nassau County, pay the highest bills, according to the survey, at nearly $100 per month. The nonprofit says that because New York American Water is a for-profit company, it has to pay for property taxes which then can be passed down to the consumer.

The rest of Long Island water providers are government entities that are exempt from paying taxes. The Suffolk County Water Authority, which serves about 80% of Suffolk residents, is among the cheapest, with bills averaging less than $30 a month.

Residents in Greenlawn in the Town of Huntington have the lowest water bills on Long Island, paying an average $12 a month.

The nonprofit says it also discovered that some districts charge hidden fees that you can't see on your bill, and some water districts don't have water. The districts just have the infrastructure and buy water from neighboring districts.

The Citizens Campaign for the Environment recommends that smaller water districts be consolidated, and that there should be a requirement that all water bills be uniform and transparent.

New York American Water provides for three districts in Nassau County, including Sea Cliff, which has the highest rate per month at $93. The other two districts have the third and sixth highest rates.