Renting a hydrant meter will allow you to avoid the sewer charges that would apply from filling a pool through your residential meter.
Another option is to install an irrigation meter, which can only be used to provide water outside the home (filling pools, watering lawns, etc.). Since water used outside doesn’t go directly into a sewer, there are no sewer charges for an irrigation meter.
Additional information is available on the How do I get a temporary meter? page.
Also, go to the Current Rates and Fees page to see the cost of installation (which will include a meter setting fee).