On Apr 7, 2:06�pm, wrote:
Often times when you install plumbing valves or electrical boxes on an
exterior concrete block wall you have to chip out concrete. Since
those are block wall once you chip it you have a six inch deep hole.

So after you installed everything, what do you do with the cavity
behind it? Do you fill it somehow?

Someone told me I should spray some foam filler in it...I am not so
sure, I have seen some of those when expanded basically "glue" onto
any surfaces, I think if I have an overspray it may expand to seal off
the shutoffs for a valve and if it's an electrical box it may be
flammable?

Any advise? leave it alone or fill it?

Thanks in advance,

MC

use expanding foam to fill voids, after cementing around at least one
side of the entrance.

you dont want air leaks, expanding foam helps keep cement from falling
in cavaties