Tubes for project heater

Well I had a picture of the tubes and just deleted it instead of
attaching it to the post... they looked like blueprint tubes but were
clear with black end caps. They were $1 a piece at the yard sale. Bought
2 since that's all they had. Figure they should do the same job as a
stack of empty cans, but it will be easy since they are in one piece.
Just need to paint them black. I may try to see if I can bleach water
with them first to purify the water. If so may not use them for the
heater project.