We’re sure there have been plenty of unhappy campers who’ve forgotten to fill their fresh water tank, then run short before the trip was over. But to overfill your fresh tank—that’s a whole different story. This family learned the hard way that there’s more to “hooking up the fresh water hose” than simply turning on the tap.
In this case, one partner offered to “help out” by hooking up the utilities when they got to their campground. Unfortunately, they didn’t recognize that the water control panel was set to “fill” the fresh water tank. It didn’t take long, and when the tank hit the full mark, it kept going. The pressure of the water in the fresh tank expanded the top of the tank high enough that it lifted the RV floor, forcing a cabinet wall up.
Fortunately, the family was still with their rig when the unwanted expansion took place. Instead of “having to fix the water tank and a few other things,” the damage could have been a lot worse. One wonders, how could the RV industry build a solution to a problem like this into their units? How about an effective overflow valve, so that if someone does goof like this, the excess water will simply blast out on the ground under the RV?
If you’ve seen, witnessed, or had your own “RV boo-boo” moment and have a photo to share with others, let us know. Fill out the form below, and put “boo-boo” on the subject line. Be sure to link your photo with the attachment tool on the form.
Other stories by Russ and Tiña De Maris
##RVT1069
Seriously? There’s no vent on the water tank fill? This would be impossible with my rig.
With the newer Nautilus systems, filling the water tank via gravity feed is no longer possible. You must either pump it in, or have pressure to fill the tank. These do have overflow devices, but on many setups once you are on the road the siphon effect can literally drain half of your fresh water. If boondocking this is not good…… so some people have taken to putting a valve on the overflow to shut it off when moving, and then opening it back up once you arrive. Of course you now have human error here……..if you forget to open it and start to fill with pressure the tank can become overfill and pressurized and expand……….not good. I’ve not seen a good answer to this problem other than to pack more water in external containers to deal with the water loss. Then you have to pump/siphon fill the main fresh water tank. Siphon filling is painful and make switching back to normal use via pressure pump wasteful as it must reverse the flow…..
Hi, great discussion and would anybody want to comment on my faux pas of over filling my gray tank in my 5th wheel that I fortunately noticed just as the water was filling the bottom of my shower (I hadn’t opened the valve between tank and sewer line). Fortunately I don’t think I did any damage!
“One wonders, how could the RV industry build a solution to a problem like this into their units? How about an effective overflow valve, so that if someone does goof like this, the excess water will simply blast out on the ground under the RV?”
Russ and Tina: You are not aware that many RVs already have this feature and have for many decades??? I can’t remember the last RV I had that didn’t have this overflow
feature. Sometime back in the 80’s, I think.
I don’t really understand this conversation, probably because I just flip open the cap at the back of my Casita and stuck the hose in turned on low. When it is full, the water runs out the top again. Simple. Works for me.
yeah, I had a casita, currently have an Escape, and before both of those, had a Starcraft tent trailer, all three, you filled the tank from a separate inlet that wasn’t a pressure fitting, and when it was full, water would bloosh out the air vent tube next to it.
Don’t know what brand RV that is but everyone I’ve owned has an over fill vent that also vents air in when the pump is running, otherwise the tank would collapse from the vacuum created when the water leaves. Suspicious of the facts on that story.
While my Arctic Fox has gravity fill – the manual warns not to “hook” the hose to it as it could cause damage to the floor. What is not clear to me is how I would “hook” the hose to it, but apparently it’s a potential real problem.
Our Country Coach HAS an overflow valve that functions just as you noted. I learned this the “hard way”, but of course there was zero damage…
Fresh tank should have an overflow/vent?
Can’t work properly w/o that. More to this story.
Often the overflow/vent is only a 3/8 line, it can’t keep up to the 1/2 or 5/8 supply filling the tank. A 3/8 tube will provide a flow of approximately 150 gph, 1/2 hose has a rate of approximately 500 gph. These numbers are approximate as a number of other factors come into play, such as pressure and length.
I think there is a difference between a simple vent tube to allow pressure equalization and a true overflow tube. The overflows I’m referring to are one inch or larger flex tubes that come out of the top of the fresh tank then bend 180 degrees down and out the bottom with a duck bill on the end. They can handle any volume a normal water hose can put in.
I agree with Tim.
Vance a 1/2″ is Pex line is only about 3/8″ inside diameter. you can’t fill faster than 3-5 gallons per minute. The vent line is usually vinal tubing and that should be 1/2″
It seems their water tank was not properly vented. I overfill mine every time I fill it. That’s how I know it’s full.
👍
I don’t understand why anyone needs to fill their freshwater tank full. Nine times out of ten you only need 1/4 to 1/2 tank as everyone hooks to local water supply when setting up camp. 1 reason would be if you are boondocking without fresh water available.
Actually, we almost never hook up to campground water except to fill our tank. We use the onboard pump for everything. The reason is if you have a leak in a wall or cabinet, you’ll hear the pump short cycle which will give an early indication of a leak somewhere.
A campground water hookup won’t give you any indication of a slow leak. It doesn’t take much water to destroy an RV.
I have owned 3 RVs and I do the same. I also turn the pump off when I leave my RV and never had an issue
Billinios’ system is the method I use. I also often don’t plug in the electricity unless the weather is cold. It makes making and breaking camp faster and simpler. For travel days I like to have everything ready to leave the night before so all I have to do is get up, eat breakfast and go. It’s kind of like boondocking in the RV park.
We always fill up before taking a trip. We never know where we’ll be at the end of the day (most of the time anyway). Plus, our water pump usually has better water pressure than most RV parks.
I actually TRAVEL with my RV and very rarely hook up to water supply. I fill my fresh tank weekly and use it exclusively. When I have gone thru 2 fresh tanks, time to dump the waste tanks, no guesswork.
Can’t imagine wasting time hooking up at every camp. Different strokes for different folks.
We only boondock and every drop of water is precious to us.
I hardly ever camp with hookups. We can camp a week on our water+holding tanks, and the DC electrics will go forever on our solar+batteries (or 6 days on zero solar)
Watching someone’s 5th wheel fall onto the bed of the truck is a painful sight. I’ve seen it happen twice.
When our fresh water tank gets full is does run out on the ground in back. Ours is a National motorhome.