If the space is too tight for you to get in there yourself, you can use an inspection camera instead. You get great flexibility since it runs on a battery and lacks a cord that can
From Amazon
LASERLINER - VideoScope XL - Video Inspection Devices - IP68 Waterproof Camera - Hard to reach areas - Diameter 9mm - Rotates 180° - Length 3.5m - Ultra Strong LEDs
Conrad Electronic
Laserliner 082.114A Endoscope Probe diameter: 9 mm Probe length: 3.5 m
ITS
Laserliner 082.114A Videoscope XL Video Inspection c/w Fixed Snake