Hi,
Had a similar problem with the pump in my TT.... to include a very slow leak on the output side of the pump.
Figuring it was the o-ring, I replaced it,... but it still leaked.
I removed the pump and mocked it up on the bench with the pickup side drawing from a bucket of water and the output side I installed a valve.
My problem ended up being fixed by replacing the fitting that has the o-ring on it.
https://www.amazon.com/Surgeflo-Fitt...omotive&sr=1-1
When I compared the fitment of the original to the replacement fitting, there was a great deal of movement with the original.
Anyway, I reinstalled the pump but it kept bugging me how did the original fitting wear out??? Since it doesn't get pulled out regularly. Then I think I figured it out. When the pump is operating, since it's mounted on rubber shocks, the pump assembly vibrates at a high frequency. The input and discharge pipes attached to the pump are hard pex tubing secured to the floor and don't move. So... with the pump viberating and the pex tubing not viberating, the fitting takes the wear.
Also to consider,... I exclusively dry camp. So compared to others that camp with full hookups my TT's water pump gets used to a much higher degree.... hence the fitting wore out.