The 225/226 requires 50" of head room with the old 225H Hot Tap Tool, 

           http://www.badgermeter.com/Industrial/Impeller-Products/Technical-Briefs/DTB-086.aspx
 

and about 30” for the HTT Tool

           http://www.badgermeter.com/Industrial/Impeller-Products/Installation-and-Operation-Manuals/872822-Model-HTT-Hot-Tap-Tool-IOM.aspx

 

The Model SDI required clearance varies, but can be computed as follows:

 

“H” Series: 

Min Clearance = Overall Sensor Length + Existing Hardware + 6”

 

“D” Series: 

Min Clearance = Overall Sensor Length + Existing Hardware + 2.5”

 

For example an “H1” installed into a 1 ½” tall welded fitting would compute as follows:

Minimum Clearance = 15.5” + 1.5” + 6” = 23”