NO COLD WATER after installing pump. Have to run hot water to get cold water
If the pump you installed was one that is located at the "point of use", when the pump runs it pulls water up the hot supply and pushes it back down the cold supply. I do not like this type of system since the result is something similar to what you are experiencing. Your only recourse is to make sure that the pump shuts off before the hot or warm water is pushed into the cold supply pipe. You may need to change the setting of the temperature sensing control to prevent this. You may need to play with the adjustments to get the best results. As I said earlier, these type pumps are a pain in the a## and sometimes are more trouble than they are worth.