Losing water out of overflow while travelling

[djousma]

All,

On the unit in my sig, we occasionally camp without full hookups. When that's the case, I prefill the water tank at home. Everytime we get to the campsite, I've lost 1/3 -1/2 of the water out the overflow. Very frustrating. My old tt had a gravity fill tank and the overflow was at the fill, so I always arrived with a full tank. New trailer, the overflow is under the trailer near the tank.

Any ideas? Self mod? Or dealer fix for this?

Thanks, dave

[Carl_n_Susan]

This is a common problem for some rigs with overflow tubes down under the frame. The sloshing of the tank as you move down the road causes water to exit via the overflow tube. Once it does, it starts a siphon effect draining the rest of the water down to the level of the pickup in the tank.

Some have relocated the overflow line so it terminates above the height of the fresh water tank. Others go for the shutoff valve which you have to remember to open when you start using the tank else you create a vacuum situation.

[ng2951]

TomHaycraft wrote:
...I've got the blue and red pex tubes for low point drains. There is then a 3rd tube, no valve, I think close to the dump valve...

I have a Grand Design Imagine 2800BH. That blue tube is the overflow for the fresh water tank. If your unit has a utility station where you can fill the fresh water tank from city water when the tank is full the water overflows through that blue tube.

The red and blue plugged lines are meant for winterizing. At the end of the year you open those plugs to drain all the water from pumps and such. The single blue valve on the passenger side of the rv is meant just to drain the fresh water tank.

At least on GD owner has reported the fresh water tank draining on its own while underway. I have not comfirmed that either, but i had an empty tank I could not explain (but the unit was serviced so maybe it got drained). It is a little difficult to believe that the tank would siphon dry in a 4 hour trip.

I filled the tank and have monitored levels. Over the last week while stationary everything shows normal.

[dedmiston]

Our old TT would do that sometimes if I filled too full or too fast. Once it formed a siphon, it would drain at least a third of the tank. I solved it by shutting off the hose every few minutes while I was filling it. Somehow yours is forming a siphon on the road. Weird.

[jalichty]

When I used to tow with a full fresh water tank, I would plug the overflow hose with a wire nut of the appropriate size and then take it out when we got where we were going. Don't tow with a full tank anymore so don't do that. Easy to do and just remember to take out the wire nut before using your fresh water. Simple and easy to do.

[Michelle_S]

A common problem with many different makes. Just go to Home Depot/Lowes/Tractor Supply, etc and get your self a shutoff and several small hose clamps. When you need a full tank of fresh water, close that valve to prevent water loss.
Seems they're making the tanks different now with an overflow hole, problem is it entends down into the tank and once the siphon action starts it continues until the water level is below that line.

[DanNJanice]

I have the same issue on a 2015 Jayco TT. Many other do as well. The easiest fix is to put shutoff valve(s) on the lines. If you put on valves make sure you label the fresh water fill and water pump switch so you remember to open/close the valves.

[djousma]

enblethen wrote:
Are you sure it is the over flow and not fresh water tank drain?

Yes. There is a third line that is capped that is to drain the tank.

[RoyB]

Interesting problem...

I don't own anything large like this but have heard that a up-suction from the roof vents may exist when moving down the roads that may pull water out of the tanks..

This is especially true with pulling fumes etc from the back and gray tanks. Might do something similar to the fresh water tanks?? I really can't imagine this is due to the fresh water sloshing around in the tanks from the trailer movement... Not up to an half a tank...

Maybe some of the 'better' fresh water tanks has baffles in them to keep the water from moving around...

I know I was surprised to see how low in height my 30 GALLON fresh water tank is. On my OFF-ROAD POPUP trailer the water tank is just 5-6 inches in height and is nestled inside my trailer frames for road hazard protection. I don't recall it ever siphons out fluids on its own...

Just thinking out loud here...

Roy Ken

[enblethen]

Are you sure it is the over flow and not fresh water tank drain?

[TomHaycraft]

djousma wrote:
Jim, I agree, just trying to get consensus if this is really a problem or if the dealer will try to brush it off as normal. Still working through the rest of new trailer bugs, so will just add this to the list to be looked at under warranty.

Yes, I've got the blue and red pex tubes for low point drains. There is then a 3rd tube, no valve, I think close to the dump valve for the freshwater tank over the axles that perplexed me initially. With no "vent" for overflow near the fill point, I've assumed this is a more direct overflow line from the tank. As I don't travel with much more than 1/3 tank fresh water (haven't dry camped ... yet!), hasn't been an issue.

[djousma]

JIMNLIN wrote:
Brand new trailer....let the dealer/mfg fix it right.

Jim, I agree, just trying to get consensus if this is really a problem or if the dealer will try to brush it off as normal. Still working through the rest of new trailer bugs, so will just add this to the list to be looked at under warranty.

[djousma]

TomHaycraft wrote:
Does the overflow have a tube or hose, that you could ... for lack of a better term, put a cork in it (or add a valve) to block or close the flow while traveling?

My Grand Design has a piece of, what looks to be pex tubing, very similar to what is used as low-point drains on many trailers.

Yes, there are a pair of pex overflow tubes hanging down. Thought of your idea. I just don't know if it's "normal" for water to apparently siphon out with this type of tank, since it doesn't have a gravity fill.

[JIMNLIN]

Brand new trailer....let the dealer/mfg fix it right.

[TomHaycraft]

Does the overflow have a tube or hose, that you could ... for lack of a better term, put a cork in it (or add a valve) to block or close the flow while traveling?

My Grand Design has a piece of, what looks to be pex tubing, very similar to what is used as low-point drains on many trailers.