Drilling clay tiles

[rudeboy]

I need to drill two 30mm holes to plumb in some solar panels. The roof has dreadnought plain clay tiles and I have a pair of lead flashings with a collar to allow 22mm copper pipes.
Two questions: What is the best drill bit for this, bearing in mind it's not going to see much use and I don't have SDS? Screwfix has some diamond tipped bits ranging from 15-65 quid, not sure whether I need water to get through roof tiles. Also where best to drill? As far as I can tell, the overlap is mostly three tiles thick, except at the bottom of each tile, there appears to be a strip where only two tiles cover would also exit between the battens. Is this correct?

 

[Burnerman]

I'd be inclined to use a diamond dust edged hole saw for this....you really don't want any accidents here!
You don't need SDS or hammer settings for these.
Your roof construction sounds to be completely normal.
John

 

[noseall]

What are these roof panels for?

Cooling water?

 

[Xenon]

Drilling the tile will lead to problems, especially the way clay moves. Tile should be removed and a lead slate made for the penetration.

 

[rudeboy]

Thanks, hadn't really given proper consideration to tile movement. The panels are old style hot water solar collectors. 15mm copper circuit enlarges to 22mm and drops through the roof to feed a secondary coil in the hot tank.

The panels were elsewhere on the roof and have been re-installed. Lead slate is effectively what I have, with a pipe-sized spigot attached. The original installation involved corners cut out of two tiles laid around the lead. I was hoping to drill through and make a neater job of it.

To allow more clearance for tile movement, could this be achieved with a bigger hole? Would 5mm around the spigot be enough?