The answer to 'how to fix repiping' is to completely replace the old plumbing system in your home with new pipes, fittings, and fixtures. Repiping involves removing the existing plumbing and installing a brand new system from the water main to the individual fixtures throughout your house.
Repiping is a major home improvement project that requires professional expertise. It's not a DIY job for most homeowners. Plumbers will need to access walls, floors, and ceilings to access and remove the old pipes, then run new pipes through the home. This can be disruptive and costly, but it's often necessary to fix recurring plumbing issues or upgrade to modern, more durable plumbing materials.