in general we are afraid of plastics. plastifobes. as such, i have gone to great lengths to get our drinking water served from copper pipes, rather than pex or pvc.
the well head is at least 130′ from the pipe entrance to the house. accounting for friction losses (water slowing as it travels over the surface), possibly several hoses running at the same time, and wanting to oversize everything i put in a 1 1/4″ line from the pressure tank to the house. you typically put in a thicker copper when you bury it, so this is type K. the walls are quite thick, but since it comes in a large roll in 60′ sections (you want as few buried connections as possible) it is also extremely soft. this means when you cut the pipe, you deform it.
copper fittings have a pretty tight tolerances. too much of a gap and all your solder will run out. i chased several connections for a few days before i finally lighted upon the best approach. i document here because the only other thing i found on the internet was twisting a crescent wrench around the top. the crescent wrench method does work fine on harder copper, but it merely chases a wave of deformation when working with the soft pipe. there are some specialty tools, but they are hundreds of dollars, and i couldn’t actually find one for 1 1/4″ – only 1″ and 1 1/2″. i think the are also only for L or M, not K.
my biggest punch was no where near big enough to get the insides to bulge, so i went to the hardware store. i believe this is a fitting for a plastic water main. the regular taper was the important part here. i just hammered it into the top lightly to get myself nearly back to square one. as mentioned above, there were puckers, or waves in the top i couldn’t remove with any combination of wrenches. this was about $3 and took them right out.
next, find a (guaranteed to be) harder copper coupling. the straight coupling is better than an elbow or something because you can see down inside it. looking straight down it is easy to see the gaps, and thus where it is out of round.
wiggle that fitting into place on top. it likely won’t slide all the way down since the pipe is still not round. now with your channel locks start to compress the pipe when you think it is sticking. it is important that you keep the fitting on the pipe while you’re doing this, preventing it from deforming. slowly work the pipe with the channel locks as you push the fitting all the way on.
once you have it fully seated, remove the fitting, and get it prepped to solder. your channel locks might have given you a bit more sanding to do, but you’ll probably be okay.