plumbing water tanks into hot water service

hello everyone,
i've installed two 9000 litre tanks out the back to plumb into the usual toilet and washing machine. as the tanks are 2/3 full i'm starting to look at getting it done.
The question is, i've also been looking at a hot water recirculator, they look expensive. As its only me and the missus, i'm thinking of plumbing the pump to feed the hot water service (gas storage type). Then installing a solenoid on say a one minute timer(would a refrigeration inline solenoid do the job?), operated by a plunger push switch? to recirculate the hot water, and vent the cool water back into the tank (which is next to the house). does this sound feasible/within regulations?

Next question, If the system your working on isn't connected to the mains, can you legally do your own plumbing? (I intend getting a plumber to do the above)(maybe)

And the last question, re: the water tank grant. theres a bit of a conspiracy theory going around about the grant stating that it's best not to claim it as there trying to find out who's got tanks so that they can tax you for it in the future. (this came from a source at Barwon water). Any thoughts? the $1k grant would pay the plumber who conveniently wants that amount to do the job.

thanks for any ideas

Gravy

More...