See >my Reply< in the same Topic in the AutoCAD Forum. [I would have done it here, as really the better place for it, but I encountered that one first.]
@dm0144 ,
I haven't inspected the other responses, but I think you need 3 parallel polylines to accomplish that; the middle one having a dashed or hidden linetype with slightly less width than the distance between the outer ones. I use that method all the time to create a Belgian Block curb line with the middle using a dot linetype. That way you can also adjust the spacing via LTScale in the Properties palette.
John F. Uhden
Hi John yes gave same answer and a line type to use in other post. For us dash is 2.4m so can count pipes.