New valve/faucet/handle/showerhead problem

Picked up this unit from Lowes today to replace my in wall valve, faucet, handles, and shower head today as I am not a fan of the old handles and the valve wasnt mixing very well anymore and there is a leak from a poor connection between the valve and the shower head thanks to shoddy work of the previous owner. When I got home I became aware that the set I picked up used a brass valve and had IPS connections (nothing anywhere says what size that I can find - not even the manual) being that I am using copper plumbing I figured I could just run back to the local hardware store and grab a handful of 1/2" threaded copper to 1/2" sweat connector as they looked to be about 1/2 inch - brought the connectors home only to find I can only screw them in about halfway - seems odd that none of the 4 adapters would screw into any of the 4 threaded connections on the new valve more than 1/2 way. What could I be missing here?? If they aren't half inch they shouldn't screw in at all correct? Threading all looks the same size seems just right but right at the halfway mark they refuse to screw any tighter.... any help would be appreciated I would really like to get this leak taken care of.

Take that unit back to Lowe's and get a pressure balanced valve. What you bought will not meet any code anywhere.

As far as the adapters not threading in all of the way, how many complete rotations were you getting before they stopped turning? Did you tighten them with a wrench or finger tight?

You will need to solder several inches of copper to the adapters, then assemble the joint using thread sealant. Than you can solder the valve in place, now that the heat source will not be very close to the threaded joints.

Any thoughts on a pressure balanced valve you'd reccomend?

Finger tight I got about 3 solid rotations. I could get one more turn with a wrench.

if you screw that adapter into that valve, THEN solder it, it will leak

also, the inerds will melt.

ips thread are tapered on purpose, it is not supposed to screw in all the way by hand

Moen or Delta for price, quality, and parts availability.

3 turns by hand with tapered threads is what you are looking for. Solder pieces of pipe into the adapters and when cool screw them in with pipe dope on the threads. You don't want to solder the pipe into the adapters after you screw them in.

Thanks for the feedback guys - I appreciate the help.