unfoulable
/ʌnˈfaʊləbəl/Definitions
1. adjective
Impossible to foul or corrupt; resistant to taint or pollution.
“The new policy aimed to make the election process unfoulable, free from bribery and manipulation.”
2. adjective
Impossible to foul or corrupt; resistant to taint or pollution, especially of water.
“The water treatment plant used advanced technology to make the water unfoulable for human consumption.”