Losing water out of overflow while travelling

At least you have a large drain. Ours is the same 1/2 inch pec takes forever to drain. I had the same issue ,went to a race track and by the time I got there 1/2 the water had disappeared . Put a valve on the over flow.once I see it coming out I shut it off

No.....it is not normal.
Mine is like yours and my water does not come out.

This is a problem with Heartland products also. There are two vent lines on my Bighorn that come out on each side of the frames rails. I got a couple caulking tube vinyl caps at Ace Hardware. I am going to get them a try on Wednesday when we tow. Chris

Mine too was siphoning. Most likely, your vent line is attached on the side of the tank...and with a line hanging underneath the trailer, uhhh....yeah, its gonna siphon. Genius design!

I'd put a small brass ball valve on it, but if you travel in the mountains, your tank should have a way to breathe and a closed valve won't allow that. On mine, the dealer, under warranty, moved the vent to a forward position on the side of the trailer. Doing so added another problem (the horizontal line collects water and won't vent).

After my tank cracked due to repeated ballooning, when I had it fixed (on my dime) I had a second vent added on the opposite side of the trailer that again hangs straight down. I close it when travelling, but having it faciliates great venting when filling and using trailer.

Both of my new vent connections are on TOP of my tank. Previously, the vent was on the side...yes, near the top, but their machine can't get the connections super close to the corner. I had the old vent plugged and new ones created...on the top. Mucho better now...but a big slosh can still push some water out an open vent.

Thanks all, for the feedback. I will be adding the ball valves. We don't travel often with a full tank, but when we do its because we are dry camping without easy access to water(even to haul). My tanks are all enclosed, heated, and insulated. Rather than having the dealer take it apart, and then telling me it is the way it is, I'll just do this myself. Won't be a problem remembering to open/close the valves. I'd prefer a through-the-wall vent, like I have seen on some other brands, but the tank is located almost at the very rear of the 5th, between the opposing slides. the only place for a through the wall would be on the rear cap, and not sure how that would go.

bucky wrote:
That gate valve on the bottom is a problem looking for a solution. The spare may be blocking it from road debris, can't tell for sure.

Just behind and inboard of the rear driver's side tire. Spare is a bit farther back.

I don't know how long Grand Design has been setting them up that way, time will tell.

The overflow lines on my fresh water tank have short rubber hoses attach that look like "duckbill" valves. The ends are formed to be pinched shut but they will allow water to pass through if there is any pressure. Always arrive with full tank.

djousma wrote:
Rather than having the dealer take it apart, and then telling me it is the way it is, I'll just do this myself. Won't be a problem remembering to open/close the valves. I'd prefer a through-the-wall vent, like I have seen on some other brands, but the tank is located almost at the very rear of the 5th, between the opposing slides. the only place for a through the wall would be on the rear cap, and not sure how that would go.

Sounds like the best plan...ie do it yourself. A valve will be needed no matter what.

My dealer 'fixed' ours under warranty via running a line forward along the underbelly to a through the wall vent further forward. However, since there is no way to run it all the way UPHILL from the tank to the vent location it had some downhill sections (eg from the tank to the underbelly) then some uphill over a frame piece, etc. Its routing made nice traps like a bathroom sink, but nowhere near as abrupt.

I took it all apart and reran it myself, and cut out most of the extra line so its tighter, but its not perfect...no way it can be unless an angling support were integrated into the trailer just for the line.

The guy who fixed mine told me something...one guy with a Class A was complaining about the same thing. He vented it straight up...Out the roof! Still would get a surge of water out of it occasionally!! It won't siphon tho!

I agree...don't vent it on the back...imagine what all will get sucked in. That seems to be one advantage of where our vent is now...forward of the wheels and up fairly high.