linking tank water to hot water system

[magennisw]

Australia being in drought has meant a lot of people buying water tanks. I recently installed a 4000 litre tank to collect roof rain water. This filled very quickly with recent heavy rains (which fall in our area but not in dam catchment areas) but I am doing nothing with it at the moment. I have been thinking of different uses for the water. Our garden uses no water so it would have to be used in the house, but putting in special plumbing for toilet flushing, cloths washing etc etc would be costly. But the tank is near the hot water system (gas mains pressure) and that got me to thinking - why not connect it to that (via on demand pressure pump)? It would then get used in cloths washing, dish washing baths and showers with no major plumbing changes involved. No one drinks from the hot tap so contamination should not be a problem. Any thoughts?

[Speedy Jim]

Bad idea, IMHO. The hot water system is a great breeding ground for...organisms. And, inevitably, there is some kind of cross-connection between your Hot and Cold supplies, whether it be in some faucet or washing machine or even the water heater. Additionally, in event of a sudden plunge in Mains water pressure, the "goop" brewing in the Hot water will be sucked into the municipal system. (I assume you are served by some such system.) If you have cisterns in the supply system, then this scenario at least wouldn't occur.

Jim