I can't siphen gas out of my 1999 dodge 1500 van?

Dodge vehicles have been equipped with a ball and seat in the gas tank filler neck since way back in the '70s. It is not an anti-siphon device, but a device to keep fuel from spilling in case of a rollover. It does serve the purpose of an anti-siphon device as only a very small hose(¼ inch)will pass it. Add a bottle of HEET to your gas tank to get rid of water. Even if you hose went to the bottom, it would not pick up the water that is in the very bottom of the tank. There are two ways I know of to check for water is drop the tank and empty it into a suitable container, or hook up a hose on the fuel rail and check what comes out..

Modern fuel tanks are built with "anti - siphon" devices in them that will not let any hose go to the bottom of the tank. You will have to remove the tank and remove the fuel pump assembly to get at the bottom of the tank. Have you tried a water remover product such as "heet"? You can remove the quick disconnect at the engine and run the fuel pump to quickly take a sample from the bottom of the tank. If you put the fuel in a clear glass container and let it set a while, the gas and water will separate giving you a good indication that you need to remove the tank and drain all the contaminated gas out and refill with good gas.

Ted is right about the tank but incorrect on getting rid of water in gas. If you are running anything but the highest octane, your fuel contains as high as 15% alcohol. Enough alcohol to allow water in gas to be assimilated into the fuel mixture. Heet and things like Christie Dry Gas are nothing but alcohol products. The highest percentage that ethanol can get is about 85%. The rest is water. If you have a really large volume of water in your gas, no amount of alcohol will assimilate it. To see if there is a lot of water in your gas, follow the instructions compliments of Auto Zone to drain some fuel through one of the injectors. Put it in a clear container. Add some fresh gas to it. If it mixes, it is gas. If it forms beads of fuel on top of the what was pumped out, you have water in your tank. If there is a small amount of water in your tank, you will not see it. While you are at it, check the fuel pressure. If it is low, change your filter first. If it continues to be low, then change the fuel pump.