It is your responsibility to comply with all laws local, state, and federal when it comes to billing for water usage.
NTEP stands for National Type Evaluation Program.
The National Conference on Weights and Measures issues an NTEP Certificate of Conformance following the successful completion of an evaluation of a device (in this case, a water meter). It indicates that the device(s) described in the Certificate is/are capable of meeting applicable requirements that are very specific and stringent as defined by the National Conference on Weights and Measures.
If you plan on billing tennants or customers for water based on measurements taken by a meter, it is very likely that you ARE required to use meters with the NTEP approval. We recommend that you check with all state and local authorities before purchasing meters that will be used to calculate billing.
NTEP Web Site