Welcome Tate!
On your 96 camper, is the fresh tank fill spout behind a small key lock door? Just want to make sure we know which vintage you have.
Does it look like this on the outside? See the little door with the sticker on it above the center of the 2 tires.
Does it look inside like this B & B molders Gravity water hatch, just the white and not the black.
GRAVITY WATER HATCH – B&B Molders
Regardless of vintage, from a 70's Sunline to a year 2000 Sunline the fresh tank fill system uses the same principals but the hardware has changed over the years.
There are 3 more normal reasons for spit back on filling the fresh tank.
1. The fill hose is too tight to the fill spout. How are you putting the fresh water hose into the fill spout? Do you have a hose piece on the end of the garden hose fitting to shove in the camper spout? Are you holding the hose end tight into the camper fill spout? I know this sounds like a strange question but if you are sealing almost all of the opening off with your fill hose, it will make the water spit back and harder to let water go in.
Some folks use something like this on the end of the hose.
Water Tank Filler
I myself just use a short piece of fresh water hose with the brass fitting cut off on one end, screwed onto the normal male end of the hose. Then push the approx 5/8" OD hose into the camper fill hose about 8 top 12 inches in. Buy doing this I do not have to hold the hose through the whole tank fill, my fill hose does not kink, and air can vent out around the fill hose.
2. The air vent to the fresh tank is plugged or kinked and will not allow the tank to vent. I'll take a guess that your 96 camper fill spot looks like what I showed above. If it has the little hinged door cover, with the door open there is the big fill spout with the screw cap on it. Next to it is a small round brass screen. That brass screen is the tank air vent. If the screen is clogged with dirt it is hard for the tank to vent. There is a silicone ring holding the screen in. Pick the ring out and the screen will come out for cleaning.
OR if you look under the camper for the fresh tank if yours is an outside tank, or next to the fresh tank if yours is under a bed etc. inside the camper, there should be a clear 1/2" vent hose that goes up to the fill spout door. If that clear hose looks all black and green inside by the tank, it may be plugged in the vent hose or the vent hose knicked. If so you have to clean that hose out.
3. The 3rd way that spit back happens is the large fill hose in the camper, about 1 1/2" OD, has a routing problem from the fill spout to the tank. If the hose goes down and then back up in a bend before going into the tank it will create a water trap in the fill hose. When the tank gets partly filled, water will spit back waiting for incoming water to work its way through the filled water trap. The only way to fix this, is to reroute the fill hose so gravity will dump all incoming water into the tank with no up and down creating a water trap. I have fixed 2 Sunline campers so far with this issue.
If this does not sound at all what you are seeing, we need some pics of the fill hose method you are using, the fill spout, the vent tube by the fresh tank.
Let us know how you make out and keep asking questions until we can help you get this sorted out. When it works right, the garden hose can be on fill open and the tank should fill venting air by itself until the tank is full to the top.
Hope this helps
John
