SWW temporary connection questions

[BotusBuild]

1. In this diagram from SWW's Site Manager Guide , what does "DT" just above the Double check valve stand for?
2. What size duct should I be looking for? 63mm external? I'll be using 25mm MDPE pipe.
3. What insulation should be used, and how easy is it to install?
4. Would it be sufficient to put up a wood frame with the standpipe and tap attached to it? Or do I need to create a box with the standpipe inside?

[PeterW]

1. Drain Tap - It is so you can drain it down in cold weather. 
 

2. 63 is fine although 110mm is better if they really want it insulated

 

3. 25x19 Polyethylene will do - Climaflex or Nomafoam

 

4. Post about a metre high and use stand offs to hold the pipe. Can always wrap the whole lot in a couple of cheap yoga / camping mats.  

[BotusBuild]

Another 2 questions

1. Where the MDPE pipe exits the insulated ducting, is there available some kind of "rubber seal" that minimizes excess water in the ground entering the ducting?

2. Is the ducting really only required as the pipe exits the ground? Buried at 750mm minimum should surely mean insulating from frost (in SW England) would be economically and ecologically unnecessary.