It is often found that small cracks in a drain line go undetected by a Video Drain Inspection. During a Hydrostatic Drain Test the drains are capped off and a water test is used to see if the system is loosing water from a leak. A smoke test can find leaks in vent drain lines when a foul odor is smelled in the house from an unknown source. Dyes can be used to detect a drainage system leak in an area not accessible by a video drain inspection.