I've managed to train everyone here to turn off the R.O. unit (with it's somewhat fragile, but valuable membrane) before turning on the washing machine. Off course, in the trade off now, I must be even more careful with those toilet seats. ;)

Another thing to do before running water to store for the fish, even with iron pipes, is to let the water run down the drain a minute before using it. That sounds terribly wasteful, but it purges the system of left over flux (the lead alloy used to seal the pipes by the faucets).

If one has new copper plumbing, it may be better to run cold water that hot into holding containers. Or wait until the teenagers have run all of the old water out of the hot water heater. ;)

If we ever have to replumb (County code doesn't allow plastic pipes here - that is unwise) I'll have to get a copper test kit. Don't know what we would do if there was a ton of copper in the water.

Copper, surprisingly, is used in a variety of fish medicines. It also shows up as a residue of tap water if copper pipes are used. If it is allowed to accumulate in any significant quantity, it can be VERY TOXIC to almost everything in a fish tank. (You could end up with no snails and no fish, a lot fewer plants, but some healthy Cryptocoryns.)

That is another reason why one is urged to get all medicines diluted and out via water changes as soon as the recommended medication period is over. It is sort of like what a drug overdose of a presciption medicine can do.