Originally Posted by fninja
Thank you to all that replied. Over the weekend I made some calls and checked it out myself. Since I do not have enough room on top of the water tank to make the tube into a loop which by the way was what the RV dealer said and someone posted (good idea and would probably stop it from draining) I have opted to put a shut-off valve at the end of the tube. So when it starts to overflow, after shutting off the supply water, I can then close it and open a faucet inside which will break the suction action. Problem solved I think. Have not tried it yet as I don't fill it until right before we get where we are going. I'll post back after this weekend and let you know if it worked or not. Have a great Memorial Day weekend. Even though I am a veteran myself I would like to give out a really heart felt thank you to all those that are serving or have served. THANK YOU and May God Bless You. Michael
I'm not sure why anyone thinks opening a faucet is going to help you. If you fill the tank until water comes out the vent and then close the vent valve, you have now trapped whatever air is in the tank. (Most vent lines actually come off the side of the tank, not the top, hence the problem.)
Adding any more water will only compress that air in the tank as the water level rises. Since the water pump suction is from the bottom of the tank, opening a faucet will not remove any of the trapped air.
If you are putting water into the tank via a gravity fill, you will be unable to, until the open faucet drops level in the tank until the air bubble reaches atmospheric pressure. But this drops level in the tank, which is not what you're trying to do.
If you are putting water into the tank via a hard-piped city water connection, you will add water until the pressure in the tank equals city water pressure. Assuming the city water is being added faster than the faucet flow, the open faucet will just reduce the rate at which the pressure in the tank will rise; but it will still rise. You might get a little bit more water in the tank, but you'll now have a pressurized tank.
If the city water is being added at a rate less than the faucet, then the level in the tank will drop, which defeats your purpose. You need to be able to remove the air above the water in the tank.
Now that the vent is isolated, you could implode your tank, unless you're getting some venting action via the gravity fill line.