Oxygen corrosion is highly localized to only about 20-25% of the piping — it is not necessary to replace the complete system.
The process of repairing a leak in a wet pipe fire sprinkler system typically involves draining the system to replace the failed piece of piping. This repair process adds enough oxygen to the system to fuel the next leak. The process of leak formation can increase quite dramatically once it starts.
Fortunately, oxygen corrosion attack is highly localized in wet pipe fire sprinkler systems and typically only damages about 20-25% of the piping. The remainder of the piping is generally unaffected by oxygen corrosion.
Dry (pre-action) pipe fire sprinkler systems generally only have corrosion-related leaks under pools of trapped water. Here again, the corrosion is localized to only a small section of the main lines where the water collects into pools. This is generally only about 20-25% of the main piping. The dry branch lines often show no corrosion because there is no water present in them. It is not necessary to replace the complete system.