Measure Your Fresh Water - there is still water in your tank!

[lmlayfield]

Have you ever thought your fresh water tank ran dry kinda fast? I did so I measured my water in and out. Turns out there is water in my fresh tank that is below the tank outlet. In my case, my 100 gallon tank has 25 gallons that cannot be pumped out - hot water heater was bypassed during my measurements.

Let me explain further. I have a 2021 Momentum 21g. This unit is listed as having a freshwater capacity of 100 gallons. This capacity is actually from two tanks hooked together to one line to the pump inlet. The problem arises because these tanks are supported by the shoulders only. There is no rigid support underneath the tanks. There are three flimsy metal straps that do not even touch the bottom the tanks when they are empty. These straps are screwed to the cross frame members and under stress they can stretch and the screw holes elongate. The tanks are 60” wide (left to right in the frame) 42” long (front to back) and the depth varies from about 4” on the passenger side to about 7” on the driver side. The tank bottom slopes towards the tank outlets on the deeper driver side. Can you imagine a plastic bottom with these dimensions supporting the weight of nearly 50 gallons of water? Even if the metal straps were once tight, they have long since stretched, along with the tank bottom. Both my tanks now have a “belly” that sags below the water outlet. Thus 25 gallons are not reachable by the pump. Even worse, most of this unreachable belly water is not able to be dumped by the dump valves. In short, everything works fine with the water system as long as there is more than 25 gallons on board.

This problem was not noticeable when my unit was new. It developed over time as I traveled with water in my tank. The 21g being a toy hauler with a generator, it is reasonable for Grand Design to expect owners of these units to travel with full tanks to use their toys in boondock type camp locations. Hauling with water weight caused this problem to occur. I did notify GD before my 1 year warranty was over, but I am still facing challenges. This is not a case of something breaking on my rig. If you replace my water tanks with brand new ones of the same design, these new ones will fail too. I have been to three dealers and a mobile tech so far. The first one replaced the water pump. The second one ordered one new water tank. It was backordered so after sitting for three months I pulled my unit and told GD I was going to get a mobile tech since I did not believe it was a water tank issue. The mobile tech and I pulled the coroplast and discovered this issue. When I informed GD they did not believe me and told me a dealer had to repair this issue. The third dealer agreed with my diagnosis of the problem and used plywood and 2x4s to support the tank bottoms using the same flimsy metal straps. I have rejected this repair as insufficient. I agree it will work for a short time, but the straps will stretch again and the untreated wood will get soft and rot and the problem returns. Now GD wants me to take it to a dealer they recommend in Indiana (I’m in Alabama).

I cannot believe I am the only GD owner with this problem. There must be thousands of units that have these shoulder supported tanks, especially in the Momentum TT line. Many of the owners are likely not even aware of this issue. Their problem may not have progressed as far as mine, maybe they use water hookups for much of their camping, or maybe they just don’t keep track of their water usage and assume the tank is empty. Not only do these unsuspecting owners have potentially a couple hundred pounds they are unaware of, they may not know there are gallons of fetid water or bleach water sitting in the fresh water tank that cannot be dumped. Whether you just cleaned your fresh water system or you thought you dumped the water out after your trip 2 weeks ago, you are adding fresh water to drink to a tank that maybe you shouldn’t be drinking from.

I really would like to hear from other GD owners on this subject. While Momentum TT owners are likely impacted by these tanks, I have heard some Imagine owners are having similar issues. I personally believe GD is aware of this issue and relying on the one year warranty to foreclose claims on the problem. If I am correct, this is not a warranty claim. It is a design issue, with potential a health hazard, that is outside the warranty - yes, I am an attorney. My goal is to see how prevalent this issue is, get GD to engineer a solution instead of passing it off to the dealers, notify all impacted owners, and fix this problem.

Please share this with others so we can find out if I got the only two defective shoulder tanks made, or if this is really a widespread issue impacting many unsuspecting owners that GD needs to address.

[DougW9876]

I found out long ago there is a lot of unusable water in most RV fresh water tanks. The biggest reason is the pickup line for the water pump is on the side of the fresh tank when it should be on the bottom, and, ideally, it would be in a sump of a couple of gallons so you should get a good flow of water right down to the last few ounces. Wishful thinking I guess because none of the RV manufacturers seem to do this.

[lmlayfield]

I don’t disagree with you. Even a few gallons is not unexpected. But 25 gallons of unusable water is ridiculous!

[Riverbug]

This isn't a new issue whatsoever. Any tank that hangs below by straps has this "defect". You black and gray tanks are the same but of course that doesn't matter so much since you drain those from the low point vs sucking from a side outlet connection. The older 80's and early 90's tanks were more rigid but still had issues with chaffing from straps and such for the same reasons. The solution is to brace the bottom as has been done with yours but rather than just using the straps, it would be better to brace from the rails side to side or similar. I have done this to an older model where 3/4" marine plywood rested on the iron which was welded to the rails on each side and had two flat bars spaced between the angle iron to help hold the middle sections. This isn't a fun job and made more complicated now with the need to remove the coraplast belly which the older units usually didn't have.

Long story to say, nothing new. Not necessarily acceptable, but that's the way all the manufacturers do it to my knowledge. And very few people take the time or expense to remedy it if they are even aware of it.

[Walaby]

Interesting.

On my Reflection, the tank drain, I believe, dumps out the bottom of the tank. I haven't dropped the coroplast to confirm this. Maybe I should. If it dumps out the bottom of the tank, wouldn't that drain all the water? Unless the sag you describe drops below the lowest point of the deepest end, where (again) presumably, the drain is.

I read through your post a couple times, trying to understand how you came to 25%. It sounds like you're measurements lead you to the conclusion that the tank sag equals approximately 25% of the volume of the tank being below the water outlet. That truly seems excessive and would be a real problem, especially if the drain is also above the sag point.

That's a crazy amount of stagnant water for sure.

Mike

[lmlayfield]

Interesting.

On my Reflection, the tank drain, I believe, dumps out the bottom of the tank. I haven't dropped the coroplast to confirm this. Maybe I should. If it dumps out the bottom of the tank, wouldn't that drain all the water? Unless the sag you describe drops below the lowest point of the deepest end, where (again) presumably, the drain is.

I read through your post a couple times, trying to understand how you came to 25%. It sounds like you're measurements lead you to the conclusion that the tank sag equals approximately 25% of the volume of the tank being below the water outlet. That truly seems excessive and would be a real problem, especially if the drain is also above the sag point.

That's a crazy amount of stagnant water for sure.

Mike

Hi Walaby -

My dump valves are out of the bottom. But the “belly” sag is so pronounced that water still remains in both tanks after the dump is opened.

My 25% number comes from actually measuring the water amounts. I used a meter for input and buckets for output. After the pump lost pressure due to air, I drove the TT on blocks under the passenger wheels. At first the pump regained pressure though it was eventually lost again. I then pulled the dumps and got additional water out of the tanks. In total, there were 25 gallons that could not be accessed by the pump when the unit was level.