Malleable iron pipe without a galvanized zinc coating is unsuitable for factories and fluid transport facilities located near ocean and lake docks. It can rust and corrode on exposure to salt and other waterborne minerals. Heavy malleable iron pipe has been replaced by PVC for household plumbing.
Malleable iron pipe is the conduit system of choice for solar heating systems. Most solar heating systems for interior heat and hot water supplies use a dense fluid to trap solar energy. This fluid becomes much too hot for PVC pipes to tolerate, but malleable iron pipe is ideal to transport it. All the fittings of a solar heat system can be made of malleable iron pipe. Malleable iron pipe is also best for cold water plumbing, as it retains its shape in the coldest conditions. Malleable iron is used for galvanized pipe fittings and can be zinc coated for rust and corrosion prevention prior to installation in a plumbing system.