2020 Momentum 25G Fresh water tank emptys

[pigag1]

I have the same problem with my 2019 295RL

[Onebadhawk]

I have this same problem on my 2017 29 RSTS.
When we bought the rig we were told the fresh capacity was 92 gals..
The brochure said 92 gals.
We boondock a lot.
The tank capacities were very important to us.
It took quite a while to figure out the tank capacity because of the siphoning issue.
When I did I said there's no way this tank is more than 60 gals.
I called GD.
They looked up the vin #.
They said the rig has a 60 gal tank in it.

Specifications subject to change without notice you know.

We've had problem after problem after problem.
We now have an electrical problem on the 12V side that I just can't find.

I have no idea what to do.
I guess I'm going to have to fine the time to drop the underbelly enclosure.

Teddy

[undermills]

Do you know how to attach a photo to this thread? I would like to show you wa
Hat my plumbing looks like. I just don’t see that the water could siphon out the top when the water level goes down below the the top vent. I would think it would lose the suction once water level goes down. We have a 2018 375 RES SOLITUDE

[offtohavasu]

Do you know how to attach a photo to this thread? I would like to show you wa
Hat my plumbing looks like. I just don’t see that the water could siphon out the top when the water level goes down below the the top vent. I would think it would lose the suction once water level goes down. We have a 2018 375 RES SOLITUDE

May not be siphoning, but water sloshing around. That water is moving around a lot in the tank with stop and go, faster and slower, left and right.

[bass mechanic]

Do you know how to attach a photo to this thread? I would like to show you wa
Hat my plumbing looks like. I just don’t see that the water could siphon out the top when the water level goes down below the the top vent. I would think it would lose the suction once water level goes down. We have a 2018 375 RES SOLITUDE

I am sure your tank looks exactly like mine, and your right it won't siphon once below the level of the top of the vent hole, from there it will simply drain until the level reaches the lowest point of the vent hole. (probably gurgle a lot)
but the point is whether your filling it on level ground and it runs out, or sloshes back and forth emptying in spurts, its all a function of gravity and a poorly designed vent location. ideally the vent should be at the very top of and center in the tank, thus water cannot exit until it reaches the very top of the tank and spills over even if not 100% level (obviously)

[rcarrell]

Update on my 2020 Momentum 25 G, has 2 fresh water tanks which emptied out the overflows every time we went camping before we got to where we were going to camp so tied both overflows together and put a SharkBite valve on the end of the tube at a easy location to get to. So went camping this week for 4 days, got to the camping area and checked the water level on the sensor panel and it was still full. I was shocked...lol Opened the valve and water ran out the overflow like there was a pump on it. I know internal pressure, yada,yada,yada. Used the fresh water for toilet, shower, cooking and when the wife washed dishes I would go out and open the valve on the overflow and filled a big roaster pan with water and she heated it on the stove. After 4 days still had fresh water, full on the sensor actually, and if I opened the overflow the water was still running out full bore. I'll pull the bottom off the trailer in the spring and replumb everything but it appears to me Grand Design has a serious design issue which they refuse to address but at least now that the season is over I can go camping.

[sgrol60]

Update on my 2020 Momentum 25 G, has 2 fresh water tanks which emptied out the overflows every time we went camping before we got to where we were going to camp so tied both overflows together and put a SharkBite valve on the end of the tube at a easy location to get to. So went camping this week for 4 days, got to the camping area and checked the water level on the sensor panel and it was still full. I was shocked...lol Opened the valve and water ran out the overflow like there was a pump on it. I know internal pressure, yada,yada,yada. Used the fresh water for toilet, shower, cooking and when the wife washed dishes I would go out and open the valve on the overflow and filled a big roaster pan with water and she heated it on the stove. After 4 days still had fresh water, full on the sensor actually, and if I opened the overflow the water was still running out full bore. I'll pull the bottom off the trailer in the spring and replumb everything but it appears to me Grand Design has a serious design issue which they refuse to address but at least now that the season is over I can go camping.

Thanks for the update. Amazing how much water will continue to flow out the "vent" line. I routed my vent lines from the middle of the RV to near the outside via a PEX line and valve that I can operate without crawling under the trailer. Then I put a removable PVC pipe on the valve that extends up above the top of the tank along the outer trailer wall. This allows the tank to vent but doesn't allow water to run out. When finished camping I remove and stow the pipe for the next time. So far it has worked well.

[powerscol]

Folks if you use the search feature there are several solutions to the problem. This is mine and I know it works so far. No water loss going over Red Mountain. Cole bank or Molas pass.
https://www.mygrandrv.com/forum/show...263#post196263

Hope it helps

[29roadster]

Why should the owners have to fix a known problem? Why doesn't GD re-engineer the vent set up?

[powerscol]

As they no longer participate here or visit I suggest calling their customer service number 574-825-9679. They have been very helpful to me. Thee is additional contact information on their web site too.
Hope this helps