Originally Posted by JRD
Much has been written on this forum about fresh water puking from the vent/overflow hose(s) during fill up and the various fixes used. I've read most of them - thank you all - but haven't been able to answer the fundamental question:
What is the cause of the siphoning problem from the fresh water tank?
1. Why does water siphon from the tank when the vent/overflow hose is arched (curled) above the level of the tank and down through the underside? Assuming the hose doesn't extend down into the tank, this seems to defy the laws of physics.
2. Why is the screened vent hole next to the filler tube opening plugged at the factory and not being used as the vent? This is the case on my WH 24RKS but may not be true of all. Our former TT used this system instead of an arched hose with no problems.
Some have argued that the siphoning does not exist, that it has to be something else. Usually, these are the people who do not have the issue or who always use full hookups.
1) How do you know that the hose is arched above the tank and does not extend down into the tank? A lot of the trailers that have this issue are ordered with the "elite" package (like mine) so the underbelly is closed and I have no idea what the plumbing looks like.
2) I think it has to do with the larger water capacity option, which is actually two tanks and so the second tank would not be vented unless they came out the bottom.
I admit, both of these hypothesis are weak at best.
Someday, when I have nothing better to do, I will take off the underbelly cover on my trailer and all the mysteries will be solved.