background
blot
blue
bubble
cement
circle
compounds
concrete
construction
crust
detail
dingy
dirty
drain
equipment
filthy
grime
grunge
industrial
industry
line
maintenance
manufacturing
mark
material
moss
nasty
old
pipe
piping
plastic
pvc
service
sewer
slough
spout
stacks
stain
supply
system
texture
unclean
unsanitary
wall
washing
water
waterspout
work