Can leaks in a radiant infloor heating system be fixed?

Yes, leaks in hydronic floor heating pipes can be repaired, but it’s not easy. The precise location of the leak needs to be identified, and then enough concrete chiseled away on either side to install a repair coupling. When the leak has been repaired and tested, it can be leveled off with fresh concrete. Although current forms of hydronic heating pipe are rated to last 100 years or more, the black pipe you mention is an earlier type that probably won’t hold on nearly that long. If it’s black polyethylene pipe, as I suspect, then it may have developed a crack in the area of the leak. But despite the difficulty involved, it’s still worth finding someone to do a repair. You might get many more years life out of your husband’s handiwork.