How to empty fresh water tank without pump?

Sorry I can't help but there should be a drain somewhere near the tank.

As far as the pump running but no water, Try unscrewing the aerator off the end of the faucet. It might be plugged up with old construction debris.

Also see if the winterizing valve is set to pull antifreeze out of a jug. That will keep the pump from pulling out of the tank.

Yes certainly there's a drain.
If you have a winterizing kit installed beside the water pump, make sure the valve is shut off before proceeding with pump maintenance.
Left open will suck air and pump runs leaving false impression that pump is shot.

And lastly, if your hot water heater was empty for this particular trip, it takes the pump several minutes to fill.

There’s a greater chance that the pump isn’t shot on a 2 year old RV and that it’s something else.
I realize you didn’t ask for advice about the issue but rather just how to drain the tank, but I’d be more inclined to find the issue than worry about draining the tank.
If you do want advice about the issue, you need to be more complete with your description of the issue, beyond “pump runs, no water come out”.

Was the Valve for pumping antifreeze into the lines turned and not turned back?

“But seeing if I can empty it before for better gas mileage”

Four hundred twenty odd pounds (50 gallons) isn’t going to make a difference in gas mileage. Dumping, driving, refilling will very boring very quickly. And forget that beautiful dry campground you just discovered...you don’t have any water.

Before you go paying a shop stick a vacuum on the faucet and use your hands to make a decent seal.

Turn both the water pump and vacuum on to prime the system. Happens to my friends trailer all the time.

pianotuna wrote:

someuser001 wrote:
But seeing if I can empty it before for better gas mileage

let's assume a 40 us gallon tank. About 300 lbs of water

The weight (measured) of my RV is 13750 lbs. But let's round that down to 13000 lbs.

300/13000 = 2.3%

I think you may be hard pressed to measure the difference in mileage.

Totally agree:) I run with about 50 gallons of H20 with a 70 gallon tank. my Milage doesn't vary with tank 1/4 full or 1//2 full about 1 mile per gallon. I always want water to use bathroom when traveling and on occasion Have pulled over in a rest area in the summer and taken a shower when the weather is hot:) All trailers have a drain peacock or valve on the bottom of the tank. Some valves extend a little below the tank.

someuser001 wrote:
The tank is completely full. So I want to avoid driving down the highway with a full tank. I guess it should be ok. But seeing if I can empty it before for better gas mileage

For the pump. It keeps running. But no water comes out the tap. Any ideas how to debug? I was going to take it to a shop

This not a trailer but a class c. Where would I find this valve. I have looked below but cannot find it. Any ideas what it might look like?

Emptying the FW tank is not going to make any measurable improvement on fuel mileage. It's frontal air resistance that affects fuel mileage way more.

There are several ways depending on your RV and it may not be necesary

Some ways: First my rig. If I follow the pipe from the tank outlet there is a quarter turn valve. I turn this and no water leaves the tank so now I can change pump safely (YIPPIE)

next is a T-fitting and the T-line runs to the pump. the Through line to another quarter turn valve to an outlet under the RV to drain (Come back tomorrow)

There is a 2nd outlet on the tank (I installed a petcock)

Some rigs if you crawl under there is either a capped pipe or a valve or both

Court of last resort.
Somewhere ABOVE the tank is a gravity fill.. Siphon hose.

But there should be a drain and a cut off valve to the pump.

I am with the person who asked if the winterizing valve was turned to the proper position. look on youtube for the procedure to dewinterize and check that valve too.