Fresh Water Tank lost capacity!

My 2014 Sundance XL fifth wheel is supposed to have a 53 gallon water tank according to the literature and the tire and loading information decal. I had not done much dry camping until this last summer. I seemed to run out of water sooner than expected.

I recently filled the fresh water tank at home and then measured how much I could draw at the kitchen sink. Thirty-eight gallons. I then went to the under trailer drain and got two more gallons.

Heartland assures me that it has a 53 gallon tank.

Anybody had this problem? Any ideas what the problem could be?

I you have a gravity fill tank, there is probably water in the vent. If this is the case, get a small piece of tubing or hose and blow the water out of the vent.

Tank 40 gal + 13 gal water heater = 53 gal. The water heater is added for total capacity.

You might also consider purchasing this water meter. It allows you to monitor the amount of water going into the RV.

Link to Amazon

SMinter said:

My 2014 Sundance XL fifth wheel is supposed to have a 53 gallon water tank according to the literature and the tire and loading information decal. I had not done much dry camping until this last summer. I seemed to run out of water sooner than expected.

I recently filled the fresh water tank at home and then measured how much I could draw at the kitchen sink. Thirty-eight gallons. I then went to the under trailer drain and got two more gallons.

Heartland assures me that it has a 53 gallon tank.

Anybody had this problem? Any ideas what the problem could be?

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Are you filling until the tank overfill starts to spill water.

Sent from my XT1254 using Tapatalk

The freshwater tank and the water heater are listed sepatetly on the tire and loading decal. 440 lbs for the fresh water tank and 50 for the 6 gal water heater so that is not it. It may be the vent blocked by water. The fill line and vent line are both come some distance from the tank to the utility compartment. I am also concerned that the tank has sagged and some water is remaining in the low part of the tank. I need to remove the underbelly to look at that but that first takes removing the gas line (or cutting the underbelly). Has anybody used tape to put the covering back up after cutting it. Does it hold OK. Of course if it has sagged, I will need to add some support to prevent that in the future.

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And yes, I am filling until water is standing in the fill fitting. If I try to put any more in it just runs out. But I guess a water blockage in the vent line could cause it to appear full while there is still a lot of air in the tank that cannot get out.

It's quite common for gravity fill systems to overflow through the fill hose if there's water in the vent line, or if there's a sag in the fill hose.

It's also not unusual for holding tanks to develop some sag.

And the feed line to the pump and to the drain, typically comes out the front of the fresh tank, not the bottom. So depending on the placement and how level the trailer is, some water in the tank may be inaccessible.

You can cut the coroplast and tape it back together. If you cut a rectangle, leave the front edge intact and fold the cut section down. Putting it back together, many people have used Gorilla Tape. A few of us have used Scrim Tape like this. I've used Gorilla Tape but the Scrim Tape works better for me.

Oregon_Camper said:

You might also consider purchasing this water meter. It allows you to monitor the amount of water going into the RV.

Link to Amazon

View attachment 55576

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Well Oregan_Camper, I also have one and it works well. I do not use full pressure and flow when using it though. It is quite accurate.

mlpeloquin said:

Well Oregan_Camper, I also have one and it works well. I do not use full pressure and flow when using it though. It is quite accurate.

Click to expand...

The best part is, I typically fill our Bighorn the day we are leaving. Which means I'm doing other last minute stuff too. I can simply look at this device and see how much water has been put in the tank vs having to go in/out of the RV and look at the "guess-timate" gauge.

danemayer said:

It's quite common for gravity fill systems to overflow through the fill hose if there's water in the vent line, or if there's a sag in the fill hose.

It's also not unusual for holding tanks to develop some sag.

And the feed line to the pump and to the drain, typically comes out the front of the fresh tank, not the bottom. So depending on the placement and how level the trailer is, some water in the tank may be inaccessible.

You can cut the coroplast and tape it back together. If you cut a rectangle, leave the front edge intact and fold the cut section down. Putting it back together, many people have used Gorilla Tape. A few of us have used Scrim Tape like this. I've used Gorilla Tape but the Scrim Tape works better for me.

Click to expand...

When using Gorilla tape I found that cleaning with soap, then at least 90% isopropyl alcohol will allow the adhesive to adhere better. Also found that putting Gorilla tape on the top side as well works better. Now your going to make me spend more money on Scrim Tape!

Our dealership hacked holes in our coroplast to unclog the furnace ducts of sawdust from the factory and put a few wood screws to help hold it up.




It didn't work (about 150 miles since 'repair hack job' at a rest stop near Pueblo, CO on our way to Tucson, AZ):



When they came to my house to 'fix' it they taped it up, but it doesn't hold very well.

I am constantly retaping both of these openings, plus I replaced all of the screws with better screws.

JohnD said:

Our dealership hacked holes in our coroplast to unclog the furnace ducts of sawdust from the factory and put a few wood screws to help hold it up.

View attachment 55582 View attachment 55583


It didn't work (about 150 miles since 'repair hack job' at a rest stop near Pueblo, CO on our way to Tucson, AZ):

View attachment 55581

When they came to my house to 'fix' it they taped it up, but it doesn't hold very well.

I am constantly retaping both of these openings, plus I replaced all of the screws with better screws.

Click to expand...

A better way to hold up your coroplast is with plastic cable/zip ties,you will need to be carful not to damage anything in the process.take a drill with the proper size bit for the ties and drill a hole on opposite sides of the coroplast,feed the zip ties thru the holes and pull tight,it will look like a zipper when finished.Cut the ends of the zip ties and then cover with gorilla tape.Had to do this to my friends unit as dealers don’t give a crap on how much mess they make or how it is fixed.This works very welll and will not fall down on the road.

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We replaced our whole run of coroplast with 4x8 sheets of coroplast (we cut it to fit) ordered from Home Depot. We used angle brackets, sheet metal screws, and lattice channels (like you use to join two lattice fences together) to hold it up. Works great and you just take down the section for where that particular tank is. We used 1/2” foil backed foam for insulation which wasn’t enough to keep water from freezing so we are going to replace or supplement that with better insulation.