I think it would depend on what part is leaking. If it is entirely in the potable water part, then you should be able to just bypass it. But, note there is probably a tempering valve installed and a flow restrictor somewhere in that mix. That is probably part of the complexity you are seeing - the tempering valve will have hot output from the coil, cold input to temper it if it is too hot, and the output of that will feed your fixtures with the house hot. Note, it could be as simple as the tempering valve has failed and is mixing too much cold water into the mix or it is turned way down, and is only set to produce warm, not hot.