How to know if fresh water tank is full?

When I first got mine, I use to play the dance of fill and run in and check, fill...etc etc. Then I talked to some people, most of which said they fill it till it "burps" back at you, then you know its full.

So I say just fill it till some water comes back out at ya. Mine usually doesn't come out the vent hole so much as it does right out the gravity fill.

Edit to add that I fill mine up at the campground, not prior to leaving for the trip. I'm fine with driving short way to the site, but I don't know how much stress 90 gal of water would put on your rig bouncing down the road.

Mine is only 30 gal, but like yours, it is enclosed.

I turn on the water then stick the hose into the fill and wait for water to come out of the vent. Then I shut off the water and screw on the cap.

Mine doesn't vent well, so I turn the hose on low and stick it in. When it starts rubbing out,I turn the hose to very low, and get a good bit more in. I also have a filler nozzle for the hose, that has a clear tube that goe down in the filler neck 8-10 inches. This does help with my venting problem, and allows me to fill a bit quicker.

It takes me a long time to fill, so if I'm not going to have full hookup at the site, I fill at home.

K Charles wrote:
I turn on the water then stick the hose into the fill and wait for water to come out of the vent. Then I shut off the water and screw on the cap.

x2

Our new Montana has a power fill only water tank and I try to check the gauge and stop at full but twice now I missed it and it started coming out of the vent. Montana says not to do this or damage can happen. I guess if you put water in fasted than the vent can let it out you could over pressure the tank and burst it. I slow it down now when its about 3/4 full.

I,too, fill mine until it burps out of the vent. I can also fill mine from the hose connection to the camper by turning a valve. But I have to monitor that closely. I usually take the filler cap off so I can see when it is full.

I fill before a trip because we usually dry camp in route. We stop at WalMarts and truck stops. My tank holds 90 gallons, also.

I will put the hose in and fill it on the slow side - til it splashes back out the spout. While it's filling, I will check the lights on the panel and they seem to work pretty good. I once filled it with the water on high and it gurgled back at me prematurely.

Pretty much do the same as others noted. I do have a shutoff on the end of the fill tube so I can cut it off before walking the 50 feet or so back to the faucet.

Letting a little water come out the overflow vent gets out any dust, dirt or road debris that might be in the overflow tube/hose. Not always a bad thing.

A time or two I've forgotten to keep and eye on the water and used "cleaning the overflow" as my excuse. Yeah...I MEANT to do that. ;)

I will fill and use the gauge. The freshwater gauge is the only accurate one I have because the tank has no debris in it.
If I don't use the gauge and fill till it over flows than a siphon will start and my tank will drain itself onto the ground.
I always leave home with a 85 gallon FULL fresh tank. Even if going to a FHU site my tank is full.