Pipes, ducts, services through masonry.

[Oz07]

Having previously mortar filled the gap between water mdpe pipe and duct I now understand cement rots mdpe. Originally a water inspector told me to do that but must of been wrong eh. 

 

So what's best plan of attack foam and wire will?

Any foam?

Insulation instead of foam? Thinking for other things like drains. 

Any wire wool? Or non ferrous?