You should be talking about 'grey water'. Google the difference between 'grey water' and 'black water'. 'Grey water' can be recycled and in most areas can be dumped into flower beds at home (not public areas) to reduce loading to the sewer system ... 'green recycling' .... This water could be dumped into the public storm system if local codes allow. Check your HD grey water disposal requirements. ... So if you can dispose of 'grey water' to flower beds or open areas, then you would not have to pay RV dumping of 'black water' fees. But some localities require grey to be disposed of the same as black water.
Bad advice! You don't want to get caught doing this. Most won't allow the melted ice from a cooler to be dumped on the ground, do you think that they will allow greasy chemical laden water to just be dumped anywhere?
Check with the hd, you should be able to dump anywhere an rv can, check public and private camp sites, public rv dumps along the roadways, rv supply stores sometimes have a dump, etc.