Greetings All, I am a homeowner in southern New Jersey. My house was built around 1893 with no plumbing. At some point plumbing was added, to create an upstairs and downstairs bathroom, and a kitchen sink which exists in an addition to the home. The bathroom drainage is visible in the basement, but the kitchen drainage goes somewhere else that I can't see. It has a separate vent. The two bathrooms are on the ground floor, which is about 3 feet above grade, and upstairs, which is about 15 feet above grade. Most of the relevant plumbing is in the basement, which is generally at grade. The pipe from the street looks like 5/8", and is reduced to 1/2" when it breaks off to the hot water heater. The cold water is also reduced to 1/2" before it makes its way upstairs. All of the pipe looks hand-bent. The water pressure in the upstairs bath is just barely adequate, and I think it could be improved by replacing some of the old copper pipe with wider diameter PEX. Doing so would increase the average diameter of the pipe, remove a bunch of old hand-bent pipe, and remove a few 90-degree bends. So, can I legally undertake a plumbing project of this nature on my own in New Jersey? Should I?