Hi all, first post and all that lovely stuff. Doing some work for my brother-in-law in his one bedroom flat he is going to rent out. He wants a new CU and condition report completing which is easy done. I've had a quick look and his meter tails are a little old, 50's built property using 10mm rubber coated tails which need upgrading. The old tails run through what looks like 3/4 inch copper pipe to a communal utilities room and I doubt there is any way in hell I'm going to get two 16mm tails and earth down there. The property is ex-council and the meter tails have been upgraded to the suppliers isolater switch but it appears no other work has been done since the installation was originally done. It is a run of roughly 10m, roughly 5m of which is outside with plenty of bends. The old copper pipe has been concreted in and I'm not up for digging up his entrance. So my question is: What size steel conduit will 2x 16mm tails and 16mm earth fit down? 20 or 25mm? I'm tempted to go down the SWA route just for ease. I have never had the urge to work with steel conduit in the past so I thought I'd best seek advice from somewhere and you'e the lucky buggers I've chosen... Thanks all.