R
Rizzle from the Portizzle
the choice here was how can i do this job without ripping it out .there was no over optionIs there a bit of a void though? I can imagine water just rushing down the back and never really having time to soak in. I can see how it might be possible on a ceiling (from above it) but can't see the wall being too safe for it. If it runs to electrics somewhere that could be risky.
Might be worth checking this out with the plasterers on plasterersforum.com maybe. See how they'd rescue this old stuff.
Personally I'd rip it out.
the plaster now is like a sponge x 5 i forget that common sence is not common .you are going to make sure that the pipe going in is not 100mm away from the inside of the wall