HELP! HELP! I have an issue with a 396 unit complex and two Evapco HVAC closed loop units. The site is six years old and has experienced a sediment problem. The plumbing is PVC off the tower and impeller pumps and copper in the stacks. Prior to my involvement the sediment built up to the point of clogging the strainers with thick black sludge like sediment. The sediment is an iron based soluble and we have a chemical treatment company that is treating it with FORMULA 1285 POLYMERIC DISPERSANT and then flushing the stacks seems to be working but the process is slow go and requires a retreatment of chemicals. I am looking for anyone who has experienced a similar problem and who has successfully overcome it. I believe that high iron content in the municipal water supply is partly to blame and that perhaps an iron filtration system between the supply line and the unit will help solve the problem.