In the past I too would make the trip to the local supermarket and refill my 5 gallon carboys with RO water. Then I bought an on faucet [Pur] water filter and tried filling my carboys with a funnel and pitchers. Today I finally switched to a large carbon water filter that is traditionally installed under the sink but instead used a dishwasher hose to connect the filter to an RV Water hose - no additional chemicals. Here is a pic of my setup in action. The system ran me about $55 at Lowes.
The parts were not made to work together but do a remarkable job with a little extra Teflon tape where the metal and plastic fittings meet, no leaks. The included filter is a 5 micron carbon and there are more ?filtery? filters available.
http://www.lowes.com/pd_55113-59019-WHK ... Id=1188335http://www.lowes.com/pd_366936-104-D60U ... Id=3579506