Hydro jetting, which uses high-pressure water to clean and clear pipes, is generally safe for old pipes. However, it's important to consider the condition of the pipes before using hydro jetting. If the pipes are already damaged or weakened, the high pressure of the water jet can cause further damage or even cause the pipes to burst. It's recommended to consult with a professional plumber who can assess the condition of the pipes and determine if hydro jetting is a safe and appropriate option.