I had my entire sewer line and had installed a backflow preventer by another contractor. However, a couple of years later after installation, I used Markham Backflow services based on a referral and I was glad I did. They were very professional and considerate of the area in the basement. They inspected floor drain, sewer line, backflow preventer and gave it a clean bill of health. They are very knowledgeable about the preventer and drains. I would not hesitate to contact Len and his team to service my backflow preventer. Highly recommend.