2011 Durango air pressure in tank

KZ built thousands of RVs with the tank vents being simply a pair of pipes going thru the underbelly. You filled the tank till water poured out of those vents. The problem is that when traveling, water spilled out of those vents and most of it was lost. Many put valves on those vents causing problems like you are having. One would need to open the vents whenever filling or using and if you ever forget just once, serious damage will result. You may have already damaged the floor, frame or other things.

The proper fix is to route those vents in a way that they exit the coach well above water level.

Check for vent hoses or pipes coming out the bottom and report back.

You need to identify how the fresh water tank is vented. Is there a gravity fill where a cap can be removed and water poured in, or is the tank pressure fill only?

The tank should not be vented into the underbelly. The fresh water tank should have no pressure and should not swell, but the bottom may sag from water weight. Describe the drains that you are finding.

Valves need to be turned a certain way to pressure fill and another way for the pump to supply water.

Since I don't know exactly what the valves look like on the trailer in question, I just made a general statement about valves being turned a certain way. My concern is not with the valves, it is the lack of a tank vent, and that quite possibly was caused by the previous owner doing something stupid like putting valves on the vent pipes.

The valve system is not like the one represented above but as Lynmor said I am not concerned about the valves as I am confident they are not the issue as there are just 3 shut offs and is quite simple. I do get reasonable pressure in the winterization line when I test it so I don't think it is a pump issue but I may swap that out anyway. The issue has to be in the vents or lack there of. There is one gravity hose attached to the bottom of the fresh water tank, One gravity hose attached to the HWT and one set of gravity hoses in the front of the trailer that I assume are for the bathroom. There is no other hoses that are visible anywhere under the trailer. I was hoping that someone with the same vintage of trailer can tell me where there vent lines typical are before I have to remove all of the underbelly to try and find them( if they are even still there).

I did remove one small piece of the underbelly that had been previously been cut out and repaired so I can see a portion of the tank and can see the gravity drain on the underside of the tank and and I can see the inlet and outlet lines on the tank but no sign of any vent lines so I may have to just remove the whole panel to see what I am dealing with as well to make sure there is no damage to the tank or trailer from tank swelling up

I bought the trailer for a really good price but was at an auction so I may be discovering why it was consigned from the dealer to the auction as they would not have to disclose this issue. Everything else on the trailer is amazing shape and everything else works 100% so I just need to get this figured out.

there is not a gravity fill that I can see

I have found the vent that I mistook for a gravity drain on the HWT. It does have a valve on it that appears was completed by previous owner. I will have to be careful when I fill to make sure it is open and that I don't put water in faster than the relief can take pressure out

Pump is still not working optimally so Think I will replace to see what I have with the new pump. Worse case I guess is that it does not fix the water pressure issue but at least I have a spare pump should I require it

A vent or drain on the water heater will do nothing for venting the fresh water tank.

Personally, I would just leave that vent open all the time, maybe even remove the valve from the tubing. I'd rather run out of water rather than expand or collapse my tank by filling or drawing from an unvented one.

Ok so I replace the pump and it is slight better but is still struggling with getting water. I am going to remove the valve on the vent tonight but there still seems to be pressure building in the tank for some reason. When I push the back up valve on the city water fill it still pushes out air and even water back out the fresh water fill. It almost seems like the pump is creating negative pressure in the tank when it is trying to suck water and creating some type of airlock possibly.

I am wondering if I drained the tank and open the gravity drain on the bottom of the tank and then pushed compressed air through the vent into the empty tank to make sure there is not a block. I currently have the tank half full and don't want to add any more water for fear of blowing up the tank without the air space currently in there.

Ultimately this is not that complicated of a system so this should not be that hard to figure out but I really don't want to remove all of the corplast underbelly if I don't have to

Just a note that the system works fine on city water but where we do most of our camping there is power but no water so I need to get this figured out

Is the fresh water overflow plugged as well (aside from the valve)? You can take a clean drain snake or fish tape and push it up into the tank to make sure. If you have an air compressor with a blow gun tip, you could also blow air up into the tube to try to clear any obstruction. That's where the air is supposed to escape or to draw into the tank to keep everything regulated.