Fresh water tank refill

Sebastian

My 2016 CS-C T@B fresh water tank doesn't seem to fill. The fill at the tow end on the driver's side accepts 1 gal then overflows. No water advances into the system w/the water pump. No leaks, only a slow drip in front of the axle on left side. I drained the freshwater tank (I think) to measure the amount of water I poured in & used a container instead of a hose to control & confirm the amount poured in.  Using the city water connection w/pressure control the water flows as it should to the faucets, shower & toilet, but I can't get the fresh water tank to fill. I've turned on the pump after adding 1 1/2 gal. & it continues to run but nothing from the faucets, shower or toilet. Advice please.  I want to travel & shower when I get to camp using the fresh water tank. Thanks much, this group has helped me before so here I am again for good advice. 
Sabastian 2016 CS-S T@B 
TV Subaru Forester

Sharon_is_SAM

It sounds like your pump is not primed.  That can happen if there is a down stream leak or inadequate water in the fresh water tank.  You need more than 1 1/2 gallons of water in the tank to prime the pump.  

Where is the overflow coming from - the fresh tank inlet or the overflow vent?  The fresh water tank air vent allows you to fill the tank, but even then, air can escape via the water inlet as you fill.  Sometimes if you try to pour the water in too fast, it will burp back.  Try filling it slowly and see what happens.

Sebastian

takes forever but also realized I should raise the front to gravity assist!

Sharon_is_SAM

Raising the tongue will allow you to fill it more.

ScottG

If possible, find and trace the vent line that runs from the FW tank to the little hole just above the filler port. It's typically a soft clear plastic hose which--if not routed very carefully, may be kinked or otherwise squeezed shut. It's also possible it could be blocked, perhaps by plastic shaving from the tank.

A blocked vent would almost certainly cause the symptoms you describe.

Denny16

You could try blowing compressed air into the vent opening to see if it is clogged.
cheers

Sharon_is_SAM

@Sebastian - were you able to fill and use the pump?

Sebastian

Not yet able to fill and use the pump.  The clear plastic hose has water in it about 5" from bottom, no kinks; I added water this am and had a burp and can hear sloshing, but I can't tell how much water is in the tank.  It flows in very slowly. 

ScottG

+1 what @Denny16 said. I actually carry a short piece of tubing in my tool kit in case I have to blow out that vent when I'm filling up at a campground.

Sharon_is_SAM

Besides the issue with filling the tank, have you tested the pump by removing the intake line and placing in a container of water to see if it will prime?

Sebastian

Tested the pump as suggested; can feel a minor amount of suction and hear water try to flow from kitchen faucet, but nothing from bathroom sink; next try will be to check diaphragm for dislocation inside the water pump?

Sharon_is_SAM

@Sebastian, disconnect both sides of the pump.  Try to draw water from a bucket into another bucket.  See if the pump works.

Pintoplumber

We have a 2016 CS S. Our water pump was sucking in air at the little water filter before the pump. Go over your connections at that point.