How could tapping into hot water line to run an outdoor line affect the rest of the hot water in the house?

Husband tapped in at hot water heater located in closet on back side of house, to run abt 15 yard line to new outdoor shower. Now water into house is not as hot. Checked the line and the meter for leaks, found none. Checked pilot light, on and working fine. Could it have anything to do with the distance of the new line?
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