Here's a good page on that scripture from Rev 3:14-16
Laodicea Aqueduct
Many people make the mistake of interpreting warm as good, cold as bad and lukewarm as even worse but the context is very local in nature, where warm water was useful for bathing, cold water for drinking and lukewarm water from the local aqueduct for neither. So they were lukewarm as in like the rest of the world and therefore good for nothing.