jimh406 wrote:

Start at the closest faucet and go from there. If you have low point drains, start there.

You also can prime the pump with some water assuming you have access to it.

mkirsch wrote:

1. Brand new camper = warranty. Call the dealer. The pump may be bad and they OWE you a replacement. You paid for it.

2. Here's a thought on the full water tank: TRY IT. It's WATER. If you find yourself unable to maintain control of the truck, or having scary moments getting the rig stopped because of the weight, or feel that its adversely affecting your fuel economy, you can just pull over and dump the water out.

However, if you are so close to catastrophe that an empty/full water tank makes the difference, you've got bigger problems to solve.