SPRINKLER TALK FORUM - You Got Questions, We've Got Answers

After having our Rainbird system repaired and additional lines added, we flushed a toilet in our home and got black looking water, which we think contained sediment. After several flushes, the water cleared, and the subcontractor claimed that we shouldn't have any more problems. However, now, every time our irrigation system comes on, the same thing occurs. The water usually turns a grey color for a little while then, after running the faucets, or flushing the toilets several times, it clears. The sub has been back twice and checked the backflow valve and the lines for any cracks/leaks and cannot solve the problem. Our plumber is also stumped. What's causing this?