How can this possibly work?

[pstandiford]

Started doing some exploring in the new unit. The water pump is under the bed with no way to get to it other than to pull some of the paneling loose. So that’s what I did. The photo shows a line that runs from the fresh water tank to the water pump. The line coming from the bottom of the photo is the line that is coming from the tank. The shut off valve (used when sucking antifreeze into the pump) is just visible. The line that tees to the right is going to the inlet of the pump. The filter is just visible on the right. At the top is the fitting that will be used to connect a hose to run to a gallon of antifreeze to suck into the inlet of the pump. OK? Now, here is the question. There is no plug in the fitting at the top of the tee. How is it possible that the water pump can possibly pull any water out of the tank? I’m going to put a plug in the fitting (like my previous unit had) but I’m really surprised that our pump does pump water. Am I missing something here? Seems like all the pump would suck would be air due to the missing plug. (Just noticed that the photo rotated 90 degrees counter clockwise)

[Beau388]

Yes there should be a white plastic plastic pipe plug in the hole. It is to be removed and an air chuck replaced in the hole to blow out the water lines for weatherization. At least that is the way my coach is plumbed.

[Elite Washington]

Mine has a white plug in it as well

[pstandiford]

Yep. I'm going to put a plug in it. But, the real reason for my post is that I am looking for one of the scholars on this forum to explain how the pump can even work. (Yes, it does work) The open line is very close to the inlet and it seems like the only thing the pump would suck is air. I guess if the water level in the tank is above the suction line of the tank the pump would have a flooded suction and would work. But if the water level in the tank is below the suction I just don't see how it would work.

[Long & Winding road]

I think my winterizer port has a valve on it just like the water tank and the water tank drain. And I dont remember a cap on it off hand. As long as that valve is off Im not worried about it. I guess your afraid it will suck air out of it? If it hasnt so far im sure your fine.