I like to use a short piece of silicone (flexible) tubing for the connection to the pump, then convert to PVC pipe. Also add a piece of neoprene or a computer mouse pad under the pump. The flex will help quiet down the pump noise. A gate valve works a lot better than a ball valve for the fine tuning of the water flow, it may be worth the trouble to replace it now. Be sure to drill a small hole in the return pipe inside the display tank just below the waterline to act as a siphon break or you will have quite a lot of water that will drain back down into the sump when the motor is turned off.