After a professional inspection, we didn't feel that there was evidence that the rat infestation was originating from the outside of a customer's home. We recommended a vapor test by the top leak detection company in our area Specialized Plumbing Technologies before they hired us to trap. The customer stated that her plumbing was working fine. I convinced her to trust me after a lengthy conversation and showing her diagrams. If I was telling her to spend money outside of my company, I was sure. This is what was found inside her wall. It was a completely destroyed plumbing vent pipe allowing rats from the sewer into her walls over and over. Our construction background is another thing that makes us different from our big box franchised competition and helped not waste this customer's money with never ending trapping. Make sure you always hire a rodent company with construction experience/education in their background.