Traveled on the 17:40 Barking - Gospel Oak this evening and the 172 DMU seemed to had sprung a leak. Just prior there was a storm and when I boarded there was rain water seeping through the seals in the ceiling panels between the driving cab and the first set of doors - the vestibule and floor was soaked. The passengers sitting in the area didn't appreciate being rained upon inside the train very much - every few moments someone was being subjected to drip, drip, drip on their head. LOL. I noticed there is some form of a module on the roof above the area where the leak was occurring - perhaps the rain was entering through this. I told the driver in the front cab as I alighted and he phone the guard in the back cab to go and investigate, don't know what happened next.