You mean, hook up Seebeck generators to your pipes in order to harvest energy from the temperature differences? It's an interesting idea. I don't think it will help much with hot-water corrosion, and it might hurt.
First, you presumably don't want to put your Seebeck generators on the pipes that run hot water to your taps, because that would make the water coming out of the taps colder. That heat isn't waste energy; it's the effect you were trying to achieve by heating the water! You'll have to put the Seebeck generators on your drainpipes only. But usually it's the supply pipes that corrode, not the drains.
That aside, I am guessing it's going to be hard to passively pull out so much heat from the water as to make a noticeable difference in the corrosion rate. Remember that the temperature difference has to remain large enough to keep driving the current through the load. And, in order to do it, you need to hook up the Seebeck generators to the pipes — you don't want to make the pipe walls themselves out of thermocouples, because then instead of a Seebeck generator you'd have a short-circuited battery, with the water in the pipe as the electrolyte. So you end up joining four or five dissimilar materials together along the wall of the pipe — a recipe, generally speaking, for extra vulnerability to corrosion, although you can avoid that by some ways of doing the joints.
In summary, I think Seebeck energy harvesting from plumbing is very promising, but not as a way of extending plumbing lifetimes.
First, you presumably don't want to put your Seebeck generators on the pipes that run hot water to your taps, because that would make the water coming out of the taps colder. That heat isn't waste energy; it's the effect you were trying to achieve by heating the water! You'll have to put the Seebeck generators on your drainpipes only. But usually it's the supply pipes that corrode, not the drains.
That aside, I am guessing it's going to be hard to passively pull out so much heat from the water as to make a noticeable difference in the corrosion rate. Remember that the temperature difference has to remain large enough to keep driving the current through the load. And, in order to do it, you need to hook up the Seebeck generators to the pipes — you don't want to make the pipe walls themselves out of thermocouples, because then instead of a Seebeck generator you'd have a short-circuited battery, with the water in the pipe as the electrolyte. So you end up joining four or five dissimilar materials together along the wall of the pipe — a recipe, generally speaking, for extra vulnerability to corrosion, although you can avoid that by some ways of doing the joints.
In summary, I think Seebeck energy harvesting from plumbing is very promising, but not as a way of extending plumbing lifetimes.