2020 Momentum 25G Fresh water tank emptys

[rcarrell]

I have a Grand Design Momentum 25G toy hauler. We have owned it 5 months. Every time we go camping the fresh water tank empties out the overflow tubes under the trailer before we get to where we are going, around a 100 miles. Been to the dealer 3 times for this issue. picked it up yesterday after the latest trip for this issue and its sitting on the street with water running out the overflow. Any thoughts?

[offtohavasu]

It's the nature of the beast, unfortunately. The easiest is to put a shark bite shut off valve on the overflow, BUT, you have to be careful. You can't fill it with it closed and you can't use your pump with it closed. There are detailed instructions on here to make it more automatic, but it will take some time, parts, and a little engineering.

[boyscout]

I have a Grand Design Momentum 25G toy hauler. We have owned it 5 months. Every time we go camping the fresh water tank empties out the overflow tubes under the trailer before we get to where we are going, around a 100 miles. Been to the dealer 3 times for this issue. picked it up yesterday after the latest trip for this issue and its sitting on the street with water running out the overflow. Any thoughts?

Simplest solution, installs in literally seconds on the overflow outlet pipe:

https://www.homedepot.com/p/SharkBit...00LF/202270643

Big caveat already mentioned by @offtohavasu: this valve should be closed ONLY when you're rolling down the road with a tank of fresh water. Should be open at ALL other times else expensive repairs may be required.

[rcarrell]

I have a Grand Design Momentum 25G toy hauler. We have owned it 5 months. Every time we go camping the fresh water tank empties out the overflow tubes under the trailer before we get to where we are going, around a 100 miles. Been to the dealer 3 times for this issue. picked it up yesterday after the latest trip for this issue and its sitting on the street with water running out the overflow. Any thoughts?

Thanks for the responses, that's what I was thinking but have never run into this issue before and I've owned more RV's than I care to think about. There's no gravity fill on the Grand Design 25G so there's no overfill up high like most toy haulers so overfill runs out the bottom in 2 places because there's 2 fresh water tanks. I'll fix it. Thanks Again.

[JCZhome]

rcarrell even though you have a solution offered, you should call Grand Design Customer Service 1 (574) 825-9679 and let them know that is an issue. When you do a factory tour they ask that even though a dealership may take care of an issue that they'd like to know about it first hand from the owner so that they can get first hand information to make the necessary changes right away.

They let us know the same thing at the National Rally in Goshen, Indiana a couple of weeks ago. If everybody that has a 25G (or all of the G series, if it's across all four models) let's them know then that will get corrected at the factory right away.

[bass mechanic]

i just bought a 2020 reflection and had the same issue. i took it in for warranty service and offered a solution. pretty simple really, the drain line needs to be higher than the tank!
furthermore visualize this..
imagine this is your tank
the factory tank looks like this


____________________ <top of tank
|-[ ]
| [____________________]
|
| <vent

here's what you need..

|----------------------------- <vent line
| ____________________ <top of tank
[ ]
[____________________]

i explained that the vent line comes out of the top left of the tank, and drops straight to the ground it doesn't take an expert in fluid dynamics to see that the issue is the when the water sloshes back and forth in this very thin and wide tank, not only does it drain right out but as the weight of the water falls out the pipe it actually creates a siphon and sucks water in behind it especially if the trailer is tilted to the left.

if you look at my diagram it is almost impossible for water to exit the vent because 1 it is above the tank, and 2 it runs the length of the tank to the right and exits on the right side.
if you tilt the tank to the left, water will enter the vent but to exit to the right would have to go uphill since the tank is tilted to the left.

if you tilt the tank to the right there would be no water present at the vent to exit.

while it may be possible to shake the tank left and right you may get small amounts of water to exit the vent but only what remains in the vent pipe if any.

so i explained this simple concept to the dealer. they called GD for warranty repair and GD said they are familiar with this issue. their solution is to install a loop of tubing on the end of the vent and attach it to the underside of the floor.
while this may work to a degree i insisted my solution is a permanent fix!
they were told by GD they would not honor my idea under warranty. (i even spoke to the warranty department personally at GD and tried to force the issue)
in the end i told the dealer to go ahead with their repair.
so their genius service tech, decided to drill a 3/4 inch hole in the right side of my tank and siliconed a 18 inch piece of clear and curled vinyl tube into the tank, made a loop and hung it from the underside of the floor thinking this would be a solution!
knowing this will only allow water to drain from both sides of the tank, i brought the rig home and proceeded to remove the underbelly cover off my brand new camper to make the repair myself!
as it turns out the water had a foul taste to it because this jackass decided to fit this tube into the tank and silicone it with a huge blob of black rtv silicone which i am quite sure is toxic to my drinking water (it tasted toxic)
i plugged the hole with a galvanized pipe plug, made my modifications to the PEX tubing.
total waste of my time to be without the camper while they made a mess out of everything.
spent 3 hours un-doing everything they did!

also worthy of note the quality built camper i thought i bought i found not a single wire or pipe under there secured in any kind of fashion. i guess they figure they only need to pay attention to detail on the parts "you actually see." if the customer cant see it, don't waste 2 dollars worth of clamps or screws to fasten anything to secure it, no zip ties, no clamps, nothing bundled together!
so now ill be removing the front half tomorrow and i have to stop at the hardware store to buy some ties and screws and clamps to i can go through the entire underside and secure everything to something so it is not just laying loose under there.
the moral of the story is this is exactly why i never pay for extended warranties!
the factory warranty is totally worthless, and there isn't anything some high school flunkie can do with a screwdriver that i can't do better with pride in my work!
PATHETIC!
FRUSTRATED!
and not worth my time to go argue with their service department.
if you ask me they owe me a new tank!
but i am not going to go back and argue with a bunch of worthless good for nothing people in the "service department" who are incapable of doing anything correctly and with any sense of pride besides putting air in my tires.
i am better off just doing it myself!
SCREW THE WARRANTY
i could replace just about any major component for less then the cost of the extended warranty anyway.

[rcarrell]

Wow, you mean Grand Design answered you, I've called them about this issue and they say they'll get right back to me because they have a number of calls on hold. I believe they probably do after the issues I've had with my trailer. The dealership I bought mine from first fix for this problem was to reposition the level sensor so I wouldn't overfill the tanks. How this was going to stop the tank draining I'm not sure. LOL Like bass mechanic it doesn't take a rocket scientist to know what the problem is and like others you suggest a fix to the dealer and no repair because Grand Design won't pay for their time to repair the issue if they are capable of fixing it. Just going to fix it myself and be done with it. Again thanks for the replies to my question. Oh by the way on the issue of hose clamps/hangers my propane hoses that run front to the rear of my unit because I have a kitchen slide were on the hoses but never attached to the under side of the unit and were just flapping in the breeze. Dealer attached 2 but left 4 unattached so did this repair myself also among others. it is pretty pathetic.

[Justonemore]

I have the same issue with my 29RS. It is in the shop being looked at I’ll post on how it was taken care of.

[bass mechanic]

ok so update to this thread, I completed my repair yesterday!
I decided to run my vent line over the top of the tank with the same size 3/4 pex tubing. once it reaches the right side, it goes forward about 3 feet, then back to the left side, then forward about 4 feet, then down and exits by the waste drain line in front of the front tire.
this way I can see through my side mirror if I am losing any water while driving!
also with a vent line this long it is virtually impossible for any water to leave the tank.

a few observations and points that I highly recommend you do this mod.

first off based on the original design, it would be impossible for the tank to fill within 1.5 inches of the top of the tank due to the location of the vent.
as soon as water reaches the lowest part of the vent, it will drain out.
for those of you who choose to install a ball valve, you'll have the same issue.

now that my line runs ABOVE the tank. I was able to fill the tank right to the top. in fact as it filled I noticed 2 things.
1. the bottom of the tank sags under the weight
2. the top of the tank rises as the water tries to climb the vent line making it possible to completely fill the tank with an air pocket towards the top.

since the tank is so wide and shallow I tilted the rig about a degree to the right as I filled it, this allowed the air to pass through the vent line and fill the tank even more.

its hard to say as I haven't calculated it yet, but if you leave 1.5-2 inches from completely full times about 6 feet wide and about 4 feet long by my estimation from the factory my 58 gallon tank was probably only able to hold 40 gallons
now it holds 58 and probably a little more.

all in all totally worth it! my problem is solved.

as for the lose wires, they must use the same wire harness in all their units. since my unit is only 29 feet I had about 12 feet of excess wire in a loom that I had to bundle up and secure under there.
I didn't take pictures, but just imagine how much wire that is at maybe a 1/2 inch thick loomed wire just laying about in the underbelly not a single wire tie!

here's the funny part, there were 2 wire straps I found bolted under the unit, and the wires run right past them like it was too much effort to remove the screw, insert the wires and reattach. if they were just a little concerned a ziptie looped through the clamp and around the bundle takes 2 seconds!

I tied up the heat duct that heats the underbelly and tanks to the vent line I ran because it was easier and sufficient to hold it in place.

if I were you, if your even just a little mechanically inclined I wouldn't waste my time at the dealer, unless they are willing to listen to some simple logic on how to properly fix this issue, I would just do it myself. otherwise pay them to do it the way I have described here.
good luck!

[offtohavasu]

bass,

Let us know how it works out!