by McDave » Mon Dec 19, 2016 12:37 pm
Hey Tommy,
If you remove volume from a container, something will want to fill it. "Nature abhors a vacuum" is the old saying. Normally air would rush in because the pressure would be greater outside tank. There is normally 1 atmosphere or 14.7 psi at your altitude surrounding everything. If either tank is vented air will replace the water at 14.7 psi. If tank is not vented the atmospheric pressure in the tank becomes lower than the atmosphere surrounding it, the outside pressure will actually hold the water in. That is known as the "thumb over the end of the straw effect". You can lift water out of a glass by holding your thumb over the end of a straw. Because your not letting air in, the pressure is lower than 1 atmosphere in the straw, so the air surrounding it will hold it in. If the two tanks are connected and only have a vent on aux, when water is removed from main, water from aux will be pushed in at 14.7 psi. . If there are no vents, eventually the pump wont be strong enough to pull the water and the tanks or hoses would start to collapse because the air outside will be pushing on it at 14.7 and the inside would effectively be at a higher altitude or less psi. Denver is at 11.5 psi at about 60f. You are a diver so you know the pressure associated with depth. It works in reverse with altitude. As a pilot we have to pressurize above 10,000ft to force O2 into the lungs and bloodstream of people who live at lower alts. or they become winded and tired and CO2 saturated. However when folks from Telluride go to Disneyworld they are a little goofy and high from all the O2 being forced in at 14.7 vs 11.0 psi... The effect is more pronounced on your engine, more psi O2= more horsepower
But I digress, and ramble. Anyways, just for shits and giggles, take the vent line from main and connect to supply or drain at bottom of aux and then vent aux. Pump or drain main and watch aux level go down. It will help if main fill cap is air tight but the water is dense and heavy and should displace or compress the air. If (when) it works, you could just mount vent line to go outside front wall and just use a barbed fitting when you want to connect aux. On a different note, that is the first time I have seen the filler inside the trailer. Is that a security deal so the non-desirables won't pee in your tank? Also, I don't see a bib for city water hook-up. Outside?
McDave
Hey, I just saw post on ac pump and inverter.That would easily do it if inverter has enough amps to power pump and pump actually works. It's worth a try. Sometimes even a blind hog will find a truffle. It might be your turn to get lucky.
