First of all, I'm not the guy who opened this can of worms;-) The pump in our Bigfoot
TT is an annoying "knocker" but it doesn't drive me crazy. I am going to try to improve the situation though. No perfection, just trying to minimize the noise. My 2 cents:
The old Shurflo 2088 in our Casita
was replaced with a Whisper King, which brought the noise level down to acceptable. We also installed a Shurflo accumulator tank (reduces the number of cycles as well as noise). Be sure to look at the specs if you plan to switch pumps. The WK is 2.0 gpm and 30 psi, compared to 2.8 gpm and 45 psi for the 2088. Less flow and less pressure with the WK! I have no experience with other brands or types of water pumps.
The pump in our Bigfoot
TT is not installed correctly IMHO. The pump is connected directly to rigid plumbing and noise is transmitted into the bathroom very efficiently. Sounds like a jackhammer. According to the instructions I have, the pump should be installed with at least a foot of flexible high-pressure braided tubing connected to both the inlet and outflow ports (like Per said). One guy writing into the "10 minute tech" series in Trailer Life swears by a 5 foot coil of tubing connected to the outlet port.
These "knocker" pumps must be mounted to something solid, like the floor of the trailer (thick plywood). The mounting screws should be neither too tight nor too loose. I tried the mousepad and it didn't help my situation. If the rubber mounts are in decent shape, I don't see how the mousepad would help.
Sometimes a noisy pump just needs to be replaced due to worn parts. If this is not acceptable to you, try tightening the screws that connect the pump to the pump motor and any other screws that might have worked loose. These pumps can also be re-built or repaired.
If all else fails, try insulating the space where the pump is mounted with some kind of soundproofing material.
I'm thinking of trying one of the Shurflo Smart Sensor pumps in our TT. Anybody have any experience with them?