big pipe
canal
chemical
cleaning water
concrete
conduit
contamination
corrosion
danger
defilement
dirty
drain
drainage
dump
ecology
environment
environmental
fall
flow
flowing
fluid
foam
garbage
impurity
industrial
industry
infection
influence
liquid
mud
natural
nature
old
pipe
pipeline
polluter
pollution
pouring
river
rusty
scene
sewage
sewer
sewerage
stream
sullage
toxic
tube
waste
water