In 1995, David Chalmers authored a paper entitled "Absent Qualia, Fading Qualia, Dancing Qualia" in which he proposes a principle of organizational invariance: "The invariance principle holds that any functional isomorph of a conscious system has experiences that are qualitatively identical to those of the original system" (http://consc.net/papers/qualia.html). He makes his argument through a set of thought experiments involving replacing some or all neurons (he assumes neurons are the fundamental elements of the organization that is the brain but this is not crucial assumption). He argues that the implausibility of fading or dancing qualia is reason enough to claim that qualia (the stuff of conscious experience) will somehow "arise" from whatever physical matter is abstractly behaving like the neurons, just as it does in the brain. He takes this to mean (contra Searle) that such diverse things as a set of water pipes or an entire population would be conscious if organized correctly. He states his conclusion thus:
"I conclude that by far the most plausible hypothesis is that replacement of neurons while preserving functional organization will preserve qualia, and that experience is wholly determined by functional organization."
Chalmers conclusion is right but his speculation about pipes and people doesn't follow. What he forgets is that functional organization requires functional elements, invariance doesn't imply (strong) functionalism. A set of water pipes can no more constitute a conscious entity than they can form a nuclear reactor core. This is because water pipes don't have the necessary functional capability: of being like neurons or fissile material respectively. Unlike the case of the nuclear reactor, however, the necessary and sufficient properties for consciousness have yet to be determined.
It may be the case that the electrical activity of neurons is their relevant property. If so then silicon chips that perform the same electrical functions would do the trick (as imagined by Chalmers in his paper): properly connected, they would be just like the brain, consciousness included. By the same token, neither water pipes nor people could form a conscious functional organization however you arrange them because they don't have the necessary electrical properties.