I have a 2013 F189FDS with a water tank way up front.
The challenge I have is getting the tank to fully drain. Neither the pump or the drain cock does an a very good job. The tank is semi transparent and it appears to be 20-25% full when the pump stops drawing and 15-20% when just draining with the drain valve.
The problem is that the bottom of the tank stretches. I had my dealer move the outlet to the lowest point of the "belly," and now it empties all the way.
Not emptying the tank completely via the pump is by design so that you don't pick up and sediment from the bottom of the tank. 20 - 25% is excessive though.
This has been a issue for me as well. I fixed the problem more or less. Do a search on my user name for more information.
If it’s stretching to a point it effects functionality, then whoever manufactured the tank engineered it poorly. Anouther example of this industry’s failure.
Moving the drain might be an option, but it would be very exposed to being caught by road debris. But I’ll ill look at it.
I had the same problem, so I unscrewed the fitting out of the tank that feeds the pump, and pressed into the tank side of the fitting a clear poly tubing that I also put a small brass fitting on the loose end to weight it that makes the end lay on the bottom of the tank at the tank's low point. The tubing needs to be cut to just the right length to reach that low point in the middle of the tank. Now my tank drains almost empty with the pump.
Rocky, that is a very clever solution -- a lot easier and cheaper than what I did (having the dealer move the fitting to the low point). I have never heard of a pickup tube intruding into the tank itself, but it makes perfect sense, after you have explained it. Well done!
I ended up doing something very similar for the line to the pump. I used a ridged tube and curved it with my heatgun to be positioned in the low point of the belly. I also installed a particulate filter to protect the pump.
The other thing I did to improve the drain is, I tilted the tank. It sits between two angle irons, one is welded in place and the back one is just screwed in place. So I lowered the one with the screes to give it some more pitch to the drain cock
Water tank draining issue
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