I installed a stand-up shower turning a half-bath into a full bath. I installed all the water feed and drain and have no leaks and all works well. My problem is that when I first turn on the hot water I get a foul smell for a the first minute of water running. The smell is coming from the water, not up from the drain. I don't have this problem in the shower/bath in the other bath room.
The new shower is tapped into the water line only 6 inches from where the other shower in the house is attached. I have 1/2 inch copper lines soldered with 1/2 inch iron pipe from the water controls up to the shower head.
Any ideas on this will be greatly appreciated.

How did you trap and vent the new shower? It may seem that the smell comes from the water but if you try my test I think you can prove yourself wrong. Hold a bucket under the sower head and turn on both hot and cold to half fill the bucket. Take the bucket outside the bathroom and smell it. Bet there is not bad odor. Test 2, dump the bucket and fill it from some other faucet then dump it into the shower stall. Bet the smell returns. I think you have a bad vent and or trap arrangement.

Sometimes the thread compound gets inside the fitting. If they used yellow rectorseal then you got to wait it out.