Losing Fresh Water Through Vent While Driving

[bclemens]

Originally Posted by Larry-NC

A loop in the overflow line doesn't help. Visualize this situation.


The real problem is that the overflow tube penetrates the tank too deeply. If it comes into the tank from the top, it should be at or just below the top surface. If the assembler sticks it in 2", then the first 2" of water can be siphoned from the tank.

Unfortunately this is not exactly accurate. There is no tube that goes into the tank. The tube does not penetrate the tank at all...some come off the top and some come off the side (at the top), but none go inside, they attached to a fitting on the surface.

The issue is when someone overfills the tank, water will FILL the overflow tube which is also supposed to act as the vent, the suction of the siphon can actually collapse the tank.

So, to "user proof" this, Forest River requires an overflow that is at least 2 times the inlet OR two overflows the same size as the inlet. We have done this for a while and 99 times out of 100, no issues...however, if someone is just not paying attention and the incoming water pressure is high, then the tank overfills again, swells, and then caps both vents with water...it starts to siphon and again can collapse the tank as it can't get air. If you can raise the overflow UP, then that solves a lot of issues, but most people don't want the overflow draining water on their nice paint job.

I am testing a low profile vacuum breaker that can mount at the corner of the tank. We'll see if we can make that one siphon under any circumstance

[Larry-NC]

Originally Posted by bclemens

Unfortunately this is not exactly accurate. There is no tube that goes into the tank. The tube does not penetrate the tank at all...some come off the top and some come off the side (at the top), but none go inside, they attached to a fitting on the surface.

The issue is when someone overfills the tank, water will FILL the overflow tube which is also supposed to act as the vent, the suction of the siphon can actually collapse the tank.

So, to "user proof" this, Forest River requires an overflow that is at least 2 times the inlet OR two overflows the same size as the inlet. We have done this for a while and 99 times out of 100, no issues...however, if someone is just not paying attention and the incoming water pressure is high, then the tank overfills again, swells, and then caps the vent with water...it starts to siphon and again can collapse the tank as it can't get air. If you can raise the overflow UP, then that solves a lot of issues, but most people don't want the overflow draining water on their nice paint job.

I am testing a low profile vacuum breaker that can mount at the corner of the tank. We'll see if we can make that one siphon under any circumstance

Hmm... Hadn't thought of the suction issue.

[Boondockin]

This crazy theory that the overflow tube siphon action is intentional. It reduces the amount of water in the tank so the straps in structure can hold the tank safely while driving down the road.

[bclemens]

Originally Posted by Boondockin

This crazy theory that the overflow tube siphon action is intentional. It reduces the amount of water in the tank so the straps in structure can hold the tank safely while driving down the road.

Lol. Not sure where people come up with this stuff.

[GarandRox]

I experienced the same issue on a past RV. I concluded that on a turn when the water hit the overflow it created a siphon. Then the water that layed in the overflow drain would restart the siphon on each turn. I was going to put an open T in the top of the overflow drain to create a vent but sold the RV. Had full intention of installing the T first thing on the new one but the drain ran straight down therefore did not retain water and also I was able to haul and maintain a full tank.

[Master gunner]

I put a T fitting on my tank with one end short pointing up with a cloth cover on it then the other goes down to the factory vent with a ball valve that I installed. Open ball valve to fill tank then close it. The shot vent will vent the tank for use.
I have had to do this on a XLR I had and on the FR I have now

[Stevemal]

Originally Posted by L98383

Our first trip out with the XL was five nights dry camping in the high desert. I had filled the fresh water tank prior to leaving, at the first fuel stop I noticed water dripping from the fresh water tank vent/overflow line.
7-hours later when we arrived the tank was at 2/3 full. It appears that driving, braking, etc. causes the water the go up and out the vent/overflow line. That was surprise I was not ready for as we lost 1/3 of the water while driving.
Suggestions?
I'm thinking maybe a shutoff valve in the line when driving? My concern is running the water pump while on the road with the valve closed may try to collapse the tank?

Have the same issue with my new Greywolf TT. I lose about 2/3rds while driving and there is 10 gals. left after the pump runs dry. Gave us one night of toilet use. I installed a pex valve on the overflow. It worked but they must not clamp the overflow/vent as water still leaks from above. It's at the dealer now, we'll see. It also sags to about an inch above the axle.

[Stevemal]

What ever happened to attaching the overflow/vent to the vent fitting by the fill port?? If that was done it wouldn't drain or siphon as that is higher than the tank. On mine just letting it hang down might have saved 2-3 feet of tubing. I'd have gladly paid for the extra tubing. They filled the vent with silicone. Strange to see other cars running wipers and flipping you the finger when it's not raining on your rig!! My dealer said it's impossible to siphon, I asked then why doesn't it stop running after you fill to overflow. He shrugged and said it was normal. Only for a FR I think! If I wouldn't have taken an $8K loss on a unit I couldn't even use last year due to all the defects, it would have been sold. No more FR's for me!

[stepdad]

I figured out how to keep the tank full without using valves or devices. I was getting 37 gallons out of a 64 gallon tank,( maybe even less if traveling). now I get an honest 57 gallons. (maybe seven gallons are left at the bottom of the tank?) This was after I made a support for the tank that wasn't supplied by Forest River. ( I had a severe sag in my fresh water tank.)
What the factory advertise is only the capacity of the tank. Not what is actually available. And no, you don't get more water from the water heater.
Don't ignore your sagging tank.

[Stevemal]

Originally Posted by stepdad

I figured out how to keep the tank full without using valves or devices. I was getting 37 gallons out of a 64 gallon tank,( maybe even less if traveling). now I get an honest 57 gallons. (maybe seven gallons are left at the bottom of the tank?) This was after I made a support for the tank that wasn't supplied by Forest River. ( I had a severe sag in my fresh water tank.)
What the factory advertise is only the capacity of the tank. Not what is actually available. And no, you don't get more water from the water heater.
Don't ignore your sagging tank.

I'm still playing the game. I used a borescope and found my leak that they couldn't find, there is no clamp on the overflow and it leaks since they added a stop valve. The dealer told me FR said not to fill the tank when traveling! After 24 hours full, my tank is hitting the axle literally. FR told me not to support it as it will take away all FR recourse!!! I called FR and they are now going to replace my tank. I've no doubt the new one will also sag down to the axle. Gotta be careful with the supports ass my camera shows the brake wires pinched under the tank!! Maybe why my brakes don't always work?!? Hopefully I'll get to use my brand new camper after owning it for a year now.

[Bill Davis]

Originally Posted by Stevemal

I'm still playing the game. I used a borescope and found my leak that they couldn't find, there is no clamp on the overflow and it leaks since they added a stop valve. The dealer told me FR said not to fill the tank when traveling! After 24 hours full, my tank is hitting the axle literally. FR told me not to support it as it will take away all FR recourse!!! I called FR and they are now going to replace my tank. I've no doubt the new one will also sag down to the axle. Gotta be careful with the supports ass my camera shows the brake wires pinched under the tank!! Maybe why my brakes don't always work?!? Hopefully I'll get to use my brand new camper after owning it for a year now.

It sounds like you folks should be posting on the Forrest River trailer forum instead of the Dynamax motor home sub forum.

[mr. peabody]

what he said n .....stuff

[Delco Bobby]

Originally Posted by Bill Davis

It sounds like you folks should be posting on the Forrest River trailer forum instead of the Dynamax motor home sub forum.

Yup ^^^

[kijak]

I just put a piece of Ductape over the vent/overfill. Barely loose any water while driving. I still see dripping and spray but in doing a physical inspection the tank is full. Even though only the level is at a third of a tank