Fresh water tank size?

Chaplee · 09-14-2021, 04:50 PM

Our “new” 2013 Sunstar supposedly has an 80+gal fresh tank. However, I can get no more than @55 gallons in it til the overflow drains. Plus, it the coach tilts even slightly to the driver’s side, the overflow drains quite a bit of water. Very frustrating to “lose” 30 gallons of water. Do I have a mislabeled tank size? Why does the overflow drain with a slight tilt of the coach?

powercat_ras · 09-14-2021, 05:41 PM

The overflow drain is on a far end of the tank, likely in a corner. The inside of the fitting that the overflow is on is slightly below the top wall of the tank. So a slight tilt towards the drain corner will allow water to begin flowing out due to siphon effect and this will continue until the level drops to an air break forms.

When I want to get the water tank really full, I fill with the coach level or tilting slightly away from the corner with the overflow.

To keep the water from being lost - Buy a bag of party balloons. Put one over the end of the overflow drain tube. It will prevent the water from running out the overflow drain tube, yet the balloon is weak enough that it will pop off or rupture before the water tank can become pressurized and break.

Morich · 09-14-2021, 05:41 PM

One of the big mistakes on asking questions is in not giving enough info to actually look at what might be happening.
With your question, we have no idea which 2013 Sunstar you have, so there is no way to look at how the tanks are arranged to actually spot any potential problems, so we have to go with just some general ideas.

One is that the tanks for Winnebago are custom designed and formed to fit in and around a lot of the other parts of the RV, so that pretty well does away with any chance the wrong tank was installed as any but the correct tank will likely not fit the space!

So if the tank is right, the next question might be how you are measuring the amount of water you put in. Is it reliable or using some meter which may not be accurate enough?

Also part of the question has to be how much water is left in the tank from the last time as the drains are placed into the tank sides and that means they rarely drain totally clear, leaving an unknown amount of water in the tank when you start adding more.

Another point which may help clear the question is where you got the info that it is a "80+" gallon tank as none listed have tank of that size unless you jump clear to the 93 gallon size. Perhaps you are not getting the correct info for your specific RV model???

Just some random guesses without knowing which specific RV you have!

Chaplee · 09-14-2021, 06:11 PM

Great tips! Any idea why I can’t get the full 80 gal??

Chaplee · 09-14-2021, 06:22 PM

Thanks for some helpful info. I have the ‘13 Winnebago Itasca Sunstar 27N. The coach manual and online specs say 81 gallons (Holding Tanks:
Number Of Fresh Water Holding Tanks: 1
Total Fresh Water Tank Capacity: 81.0 gal.
Number Of Gray Water Holding Tanks:1
Total Gray Water Tank Capacity:53.0 gal.
Number Of Black Water Holding Tanks: 1
Total Black Water Tank Capacity: 43.0 gal)

I was using an inexpensive Flow meter to gauge the amount of gallons going in (it could easily be incorrect). I also notice that the interior fluid level panel will go to full/green after a supposed fill, but very quickly goes down to 1/3 full. I suspect this is all a combination of things, as you suggested. Appreciate the response!

Morich · 09-14-2021, 07:58 PM

Okay we can get down to some differing ideas as Winnebago does a great job of posting online drawings and after the year 2010 year, there is an interactive setup where we can go to drawing and almost get a "superman" look at things as we can "look through walls" and turn things over and around as well as zoom. It takes a bit of download of a program and then some practice learning to "drive" the thing but it does lots of neat things to let us see what's in the RV!
Parts catalog here:
https://catalog3d.winnebagoind.com/menu/Parts.htm

After some clicking on the correct RV and correct part we want to look at, we can get this picture, which I took a snip of and marked some things of interest.
First thing I checked is the list that comes with the drawing and it has a conflict with the info you have as it lists the tank size as 64 gallons! That is a big start on where the extra thirty gallons went?

Somewhere there is a glitch in info you have and what the parts info says. I'm guessing from what you say, that the parts is correct for tank size but then there are several other things that you might want to look over as well to explain some smaller points.

Click these snips to get a bigger/better view if you can. But one big thing is the shape of the tank as being a long flat shape more like a mattress, perhaps? That makes any lean in the RV toward the driver's side, push the water toward the end where the in and out happens!
Looking at all sides of the tank, I found ALL the openings are on this end, starting with the gravity fill port and then there is a small vent line that comes out under the gravity fill cover. Much easier to get water in if you have a vent to let air out!

Then at the front corner on the driver's side is the city water fill, big drain, and the overflow where it seems water if coming out too soon? So you see when you drain, the drain is higher than the actual bottom of the tank and if the RV happens to be tilted toward the passenger side to pointed front uphill, the drain will leave some water in the tank.

So what I see is the conflict in size, combined with potential for the RV to be tilted one way when draining and the other when filling, can make you only getting far less than 80 gallons put in before it runs out the overflow.
if this is one of the milky white tanks, you may be able to spot the water level in the tank by looking behind the water pump I see on the far end if there is access there?

So there is a real reason for what you are seeing!!
Bummer, perhaps but still better to know the what and why?

Chaplee · 09-15-2021, 05:54 AM

Wow! Had no idea such data was available. I’d had trouble finding the right sites with Winnebago and your email explanations are great. I’ll be looking at those diagrams soon!

Morich · 09-15-2021, 07:20 AM

It's a great way to spot how the potty drains, too!
If you do go to that site, there are a few hints that are not explained on using the interactive part.

Down in the lower left when you get to the plumbing, etc, there are three small symbols to effect how the display centers on things. Choose which direction you want to view from (front,back.left,right?) at the lower right, then if you want to look at some specific item like the converter, before zooming, etc, go to lower left and there is a cross looking thing to click. Click the symbol and then on the item and it then keeps the display centered on that item as you move to run, zoom, etc.

Danger here:
You may get the RV turned over and so dizzy you have to backout and start over! Fun things to drive!

Ksean · 09-19-2021, 05:49 PM

I got tired of the siphon effect draining 25% of my fresh water while driving before I even got to my destination so I added a shutoff valve on the overflow pipe. Now when I fill my tanks I open the overflow valve and fill until they overflow then I shut off the overflow valve and stop filling. When I get to my destination I open the valve and enjoy. The amount of water I have now makes my camping all that much more enjoyable. The only trick is to remember not to fill the tanks while the valve is closed or you could rupture a tank.

Morich · 09-19-2021, 05:57 PM

Quote:

Originally Posted by Ksean

I got tired of the siphon effect draining 25% of my fresh water while driving before I even got to my destination so I added a shutoff valve on the overflow pipe. Now when I fill my tanks I open the overflow valve and fill until they overflow then I shut off the overflow valve and stop filling. When I get to my destination I open the valve and enjoy. The amount of water I have now makes my camping all that much more enjoyable. The only trick is to remember not to fill the tanks while the valve is closed or you could rupture a tank.

Just as a small note to ease your concern, perhaps? If you look it over, there are actually a couple other places for air and water to vent out without the overflow. One is the vent line going up to the area of the gravity fill and then the gravity fill itself is just a big pipe going into the tank and the flap covering it is probably not going to be tight enough to allow the tank to blow?

Any excess water does go out the overflow because it is lower but there are the two other routes if that is blocked.

Chaplee · 09-19-2021, 05:59 PM

Did you install the overflow valve outside the coach or inside the plumbing system somewhere? A sensible solution!

Ksean · 09-19-2021, 06:14 PM

My two water tanks are accessible inside one of my storage compartments and that is also where my overflow drain pipe is so I just cut into the overflow pipe and installed an in-line ball valve it works awesome and it was a very simple mod.

Morich · 09-19-2021, 06:21 PM

It looks like there is a drain valve right next to that overflow, so maybe you can see and reach that area and a new valve in the pex would be an easy out?

But then I'm also here in my easy chair, not hanging upside down under an RV, trying to see!!

Chaplee · 09-19-2021, 06:24 PM

I think i"ll try a new valve just where you pointed it out. Easy access...should be easy.

fwpeters · 04-17-2022, 08:17 AM

Just saw this thread and I wanted to jump in and ask what material is the fresh water tank made of? HDPE or polypropylene ?

Chaplee · 04-17-2022, 08:42 AM

I installed the valve near the bottom of the overflow tube. It worked!! I’ve since sold the unit.

Morich · 04-17-2022, 09:34 AM

Not enough of a plastics guy to know the difference, so did a look of online and found some info.
But it comes with the idea that ALL online info needs to be checked to use this with care!
QUOTE:
Varying in size and location, RV water tanks are usually made of ABS or polyethylene plastic. There is one for fresh water, gray water (waste from sinks and showers) and black water (waste water from a toilet). Here's what you need to know about these three types of water tanks and how they work in an RV.Oct 18, 2021

Keep in mind that most online info is meant to sell, distort, or mislead, so don't believe it until you check!