This study has shown that higher levels of carbon supported greater biofilm growth and planktonic populations on the materials that were tested, although the effect was most pronounced on iron pipe. Utilities with significant amounts of iron pipe in their distribution systems may be faced with the greatest regrowth potential. For utilities that also distribute water that is high in natural carbon, this problem may be compounded. Therefore, reducing the organic carbon in the finished water may be effective for any utility wishing to reduce regrowth problems in their distribution system. Other alternatives for utilities wishing to reduce biofilms in the distribution system can include any or all of the following: replacing or relining iron pipe in the system, increasing disinfectant, and implementing effective corrosion control. Originally published by AwwaRF for its subscribers in 2003