Location of plastic ducting in walls?

Hi,

I am putting in a HRV system in my self build which means that I have some plastic pipes running down the external and internal walls. My plasterer is starting next week and I wanted to check if there is any standard way of marking where the pipes are in the walls for the future? I took pictures of the walls b4 the plasterboard was put up but maybe there is a more common/better way of marking these? Also, is there anyway of protecting the pipes?

Lastbuilders

I was going to suggest something like this:-
Bosch PDO Multi
http://tinyurl.com/nyzso
But it doesn't detect plastic...

I saw one of them in B&Q at the weekend but as you have said it won't detect plasic. Maybe I can run a wire alongside the plastic???

Lastbuilders

Are you securing the plastic pipes to battens? The PDO would detect the battens... But yes, it strikes me that wires would work
I'm sure that there's a standard builder's trick for this - which someone more knowledgeable than me can share...

You could fix (with a bit of tape) a galvanised cheap wire (or copper) onto the ducting. Galvanised wire because it would'nt rust even in the long term. Usually a drawing (or photo)is sufficient, but sticking to the standards plus a photo is even better. "The standards" are the ideal distances to openings, floors, corners, the right angles etc...buy a book about the issue.
Once the ducts are filled with a cable they're detectable anyhow, as the Simp said so already.
More important are burried junction boxes. For these they use (on the continent at least) lids that come with a red, thin, half stiff polyethylene thread sticking out.The plasterer can overplaster them but the thread comes jumping back through the wet plaster, sticking out of the wall/plaster waiting for the electrician.