unexpected & unexplained water draining from my fresh water drain

[dsm]

We are in our 1st year of TT ownership. We have a 2018 2304DS Ultra Lite.This weekend was our 4th excursion in the trailer.

This past weekend I woke on the first morning and found a large puddle under the trailer, the puddle sourced from the fresh water drain. I have not dry camped in the trailer yet, and I have never filled the fresh water tank. I had never experienced this before. Again, since I never used the tank I wasn't aware that the drain was open. I figured out where the closed position on the drain valve was and closed the drain.

Preparing to leave camp I opened the fresh water drain and proceeded to empty 4.5 gallons (I carry a 3 gallon bucket) of water from a fresh water tank that I have never filled. So I figure I have a problem, but I don't know what it is. Can anyone offer some insight and possible solutions?

Thanks.

[Flybob]

This is very common and is caused by the back-flow valve in the water pump not seating correctly. Here is a simple fix.

Make sure water pump is off.
Turn off city water at campground source.
Run water in a sink until it stops.
You will need a little water in your FW tank
turn on water pump and allow water to flow from a faucet for about 30 sec.
Shut off water faucet and turn off pump
Turn on city water again and you should be OK.
Do not run the water pump when you are on city water.

[clr]

Well I am not knowledgeable of you each brand and model there are two common causes for your problem.
First is that the check valve associated with your water pump is leaking city water backwards into the fresh water tank. The easiest fix for this is to place some water in the tank and use the pump to move water in the other direction, this will many time flush what ever is causing the check valve to not fully seat.
Second many units have a method of using city water to fill the water tank. You may of turned the valve on for a time and that caused water to be in the tank.