What could be causing the pumps to be noticeably loud?

In our experience, there are three factors that cause excessive noise: 1. The pump may be placed on a console (wooden board, metal console) that acts like a sound box. Measure: Place the pump on a foam mat or on the floor. 2. The pump may be next to a smooth wall, which reflects the noise and multiplies it as a result. Action to be taken: lean a foam mat against the wall (ensure there is no contact with the pump!) and this will absorb the noise. 3. The inlet pipe and/or outlet pipe of the pump may be made from hard or even metal tubing that carries the noise from the pump. Measure to be taken: the pipes upstream and downstream of the pump should be made of at least 50 cm of flexible hose. You can find further information about connecting pipes in the operating instructions for your pump.