Fresh Water Tank Vents

[OHAPP]

Recently purchased a 2020 Momentum 21G, filled fresh tank, after three hour drive tank was down to 2/3. Water was coming out the blue tank vents, almost like it was siphoning. Can I plug these while traveling, pull plugs when in use or filling? Any one else experience this? Thanks

[Jkwilson]

You can, but there is a risk of damage if you forget. There is a mod to add a second vent to avoid the siphon effect.

https://gdrvowners.com/forum/operati...problem-solved

[Cate&Rob]

I would be curious to learn whether your 2020 model has the twin blue vent tubes or just a single one.

Rob

[TedS]

The twin vents do not prevent loss of water due to sloshing.

[COReflection]

Recently purchased a 2020 Momentum 21G, filled fresh tank, after three hour drive tank was down to 2/3. Water was coming out the blue tank vents, almost like it was siphoning. Can I plug these while traveling, pull plugs when in use or filling? Any one else experience this? Thanks

I know I may be the odd-ball here but I've noticed that many brands of campers work similarly and will leak water out of the freshwater tank when driving. That happened to me with our first big trip with the Keystone Montana that we had. I quickly addressed the problem for the next trip and added shut off valves to the bleed and vent lines. It worked great and I never lost any water during traveling ever again.

On my new GD Reflection, I do have the two siphon/air/bleed blue lines hanging down by my FW tank and also added two SharkBite valves. I keep them open when filling, close them both during traveling, and then open the furthest one from the tank once I get to my destination. The warning about collapsing the tank I'm sure is valid if you were to extinguish a good number of gallons of water without allowing air in but in my case, I just make it part of my pre-departure and arrival list of tasks, and all is well. I would rather arrive at my boondocking campsite with all the water I loaded at home.

[Cate&Rob]

If you read back through the long story of developing the twin vent tube design . . . sloshing in a nearly full tank can start a siphon action that actually draws in the top and bottom of the thin walled tank, reducing the tank volume and keeping the water level above the vent connection and continuing the siphon. The twin tube design breaks this siphon action. This design will not stop water loss due to sloshing during driving.

There are designs posted on this forum for routing the vent line to a higher point where sloshing cannot start a siphon. This is more complex but is a fail-safe design. Shut off valves are a simple and positive fix . . . but, damage to the tank is quite possible from that one time when you got distracted while filling or drawing water from the tank and forgot to open the valve(s).

BTW, Grand Design advises against travelling with a full water tank. I am not agreeing or disagreeing with this . . . just noting their advice.

Rob

[TedS]

Have to disagree with 'more complex '. No more complex than gravity fill plumbing with tank vent.

[COReflection]

There are several posts on multiple forums about pulling the camper with a full tank of water. While I know there are some cons such as sloshing of the water if there aren't baffles in the tank, poor tank supports or supporting structure, more weight and possible towing characteristic changes....but I will speak for myself and how we use our camper. We boondock 100% of the time all through the summer. There is literally nowhere that I can fill up my tank once we get to our destination. We have to leave home with our water tank full and we also prefer our softened well water from our house rather than some of the other locations we visit. I'm not sure it's practical or reasonable to believe that most who boondock won't fill up before they leave the house. In the case of my new Reflection, I already dropped down the chloroplast to inspect the tank supports to ensure they are adequate for pulling with a full tank and they are in my opinion. I'm not trying to win anyone over either---just stating how we use ours.

[OHAPP]

Thanks for the reply’s, ours does have the dual blue vents, one on each side of axles. Thinking about capping with a small hole to allow water and air to escape if I did forget to uncap while filling. This would reduce the amount lost due to sloshing while traveling with out building pressure?

[Jkwilson]

Thanks for the reply’s, ours does have the dual blue vents, one on each side of axles. Thinking about capping with a small hole to allow water and air to escape if I did forget to uncap while filling. This would reduce the amount lost due to sloshing while traveling with out building pressure?

You’ll be filling or draining faster than the vent can work. Still have a risk.