For aesthetic reasons, you will certainly have to paint all or part of the piping, especially the large PVC pipes used for the evacuation of wastewater. Always work on clean and dry substrates, for a better adhesion of the paint.
To treat hot water copper pipes, it is advisable to use special paints of the type used for radiators, which withstand a high temperature. This will prevent the paint, quickly enough, blisters or flakes.
The most difficult is to avoid the peeling of the paint. It must therefore take any measure allowing the film to adhere properly, including making the medium slightly abrasive sanding.
Do not try to save too much paint, and of course eliminate all leaks in the pipes.
The substrate must be clean, dry and dust-free.
Degrease with acetone: rub in the same direction to repel the residues.
Another solution: pickle the copper with fine iron straw. The result is impeccable when the copper returns to a brilliant color.
Mix the undercoat thoroughly so that it is consistent, then apply it to the pipe.
Allow to dry for at least 12 hours, then apply the color.
Do not over-stretch the paint and apply a second coat.