Water Siphoning from Full Fresh Water Tank

[ThePowells]

Ray&KatinCR Welcome to the family and the forum!

[Ray&KatinCR]

Thank you for the welcome Jerry and or Kelly
Ray

[Ray&KatinCR]

Well we got er done. First valve I ordered used a solenoid operated flapper and I could barely blow thru it (more restricted than I was comfortable with) so I ordered a solenoid operated ball valve that closes with lights off and I hear it close. final test will have to wait till next June when we will be heading to SLC for a week but I feel pretty good about it. power applied and opens automatically when power is off, no restrictions. got it mounted under there and ran the wires back to the rear lower marker light. plugged it into my truck, lights on and I can hear it open,

[Country Campers]

Ray&KatinCR

This is a great idea. So if I understand this when the trailer marker lights are on the valve is closed, no water getting out, if the trailer lights are off then the valve is open and air can get in. This would definitely avoid the "did I open the valve or not" situation.

Brian

[OurNewEra]

[QUOTE=Ray&KatinCR;n66648]
Well we got er done. First valve I ordered used a solenoid operated flapper and I could barely blow thru it (more restricted than I was comfortable with) so I ordered a solenoid operated ball valve that closes with lights off and I hear it close. final test will have to wait till next June when we will be heading to SLC for a week but I feel pretty good about it. power applied and opens automatically when power is off, no restrictions. got it mounted under there and ran the wires back to the rear lower marker light. plugged it into my truck, lights on and I can hear it open,

[QUOTE]

Along those same lines, wouldn't a sprinkler/irrigation valve with a solenoid work? I think it would.

[Ray&KatinCR]

Ray&KatinCR

This is a great idea. So if I understand this when the trailer marker lights are on the valve is closed, no water getting out, if the trailer lights are off then the valve is open and air can get in. This would definitely avoid the "did I open the valve or not" situation.

Brian

I do suffer from "CRS" so uh yeah.... I used the marker light circuit because my back-up camera is also on that circuit. shut off when fueling up and back on when under way. I'm thinking the stop should relieve any pressure build up and hopefully prevent any damage to the tank.

[Ray&KatinCR]

[QUOTE=OurNewEra;n66657][QUOTE=Ray&KatinCR;n66648]
Well we got er done. First valve I ordered used a solenoid operated flapper and I could barely blow thru it (more restricted than I was comfortable with) so I ordered a solenoid operated ball valve that closes with lights off and I hear it close. final test will have to wait till next June when we will be heading to SLC for a week but I feel pretty good about it. power applied and opens automatically when power is off, no restrictions. got it mounted under there and ran the wires back to the rear lower marker light. plugged it into my truck, lights on and I can hear it open,

Along those same lines, wouldn't a sprinkler/irrigation valve with a solenoid work? I think it would.

It would have to be a normally open valve that will automatically open when power is off. to work the way I use it.
this is the valve I ended up using, no restrictions.
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

[Saxles]

If we combine the observations made by Neil, the calculations and the vented loop ideas suggested by others . . . the solution to this becomes very simple . . .
The problem comes down to a 10" water column siphon action that generates enough vacuum to draw water out of the tank, collapsing the tank bottom and top, reducing tank volume.

Addition of a T and a second vent line to the existing first vent line should solve this problem. The second line must be a different length than the first, so that (if these two lines both happen to fill with water) the pressure/vacuum differential between two different vertical heights of water column will cause the longer one to drain the shorter one and then the shorter one will break the vacuum in the first one. See attached diagrams.

Now we just need someone (who has experienced this tank collapse draining) to install this simple modification to see if it works.

Rob

Water Tank Vent.pdf

I want to thank Rob for this design. I modified my 2018 150RL Reflection and incorporated this design. I have used it for most of the summer. We mostly take on water at campsites (if needed) but last week we filled the FW tank completely for a short trip to Algonquin park. We always carry some water for coffee/bathroom breaks. I did put shutoff valves on both lines. I have no problem remembering to open/close them. This design works flawlessly.
in addition, I was able to obtain about 6 more gallons of capacity. Rob’s drawings show the vent line looping up above the top of the tank. On my trailer the vent line came out of the tank and dropped straight down. I was able to reroute the line to give me the full capacity of the tank gaining more than 6 gallons.
I am really happy with this “fix”.
Thank you Rob.

[Country Campers]

I want to thank Rob for this design. I modified my 2018 150RL Reflection and incorporated this design. I have used it for most of the summer. We mostly take on water at campsites (if needed) but last week we filled the FW tank completely for a short trip to Algonquin park. We always carry some water for coffee/bathroom breaks. I did put shutoff valves on both lines. I have no problem remembering to open/close them. This design works flawlessly.
in addition, I was able to obtain about 6 more gallons of capacity. Rob’s drawings show the vent line looping up above the top of the tank. On my trailer the vent line came out of the tank and dropped straight down. I was able to reroute the line to give me the full capacity of the tank gaining more than 6 gallons.
I am really happy with this “fix”.
Thank you Rob.

So you say that you have valves on both lines, Did you travel with the valves open or closed?

Brian

[Saxles]

Mostly closed, although a few times travelling between campgrounds ( maybe 3 times) with the tank a third to a half full I left them open. We were in a lot of provincial parks this summer, many that are hilly, so I usually close the valves when taking on water when going in. I also closed them for the one trip we took with a full tank.
If you are on an uneven slope with driver’s side low enough I don’t think there is anything to stop the water from running out other than the closed valves. However there is no ‘syphoning’. The two lines are effective in stopping that.

[Country Campers]

Mostly closed, although a few times travelling between campgrounds ( maybe 3 times) with the tank a third to a half full I left them open. We were in a lot of provincial parks this summer, many that are hilly, so I usually close the valves when taking on water when going in. I also closed them for the one trip we took with a full tank.
If you are on an uneven slope with driver’s side low enough I don’t think there is anything to stop the water from running out other than the closed valves. However there is no ‘syphoning’. The two lines are effective in stopping that.

The 2 lines are supposed to stop the syphoning without the need of valves, this is the whole idea behind the 2 lines.

Brian

[TedS]

The valves stop the water loss due to sloshing during travel.

[Cate&Rob]

Saxles

Thanks for the feedback . . . and welcome to our forum.
Grand Design has implemented the double vent in production, but you are the first to report a retrofit to an earlier production trailer.
This design will prevent a siphon action from starting with tank sloshing, but will not prevent a small water loss from the initial slosh.

Rob

[Guest]

The double vent invented by Rob is brilliant but will not solve the sloshing issue. To compliment the double vent lines, a baffled tank is needed. I priced out a custom baffled tank for my Imagine from Protank out of TX and it was very expensive at $637.50, but mass production could drastically reduce this price. So if GDRV wanted to add a baffled tank to solve the sloshing issue, it could be done.

Jim

[Cate&Rob]

An even better solution would be to run the tank vent to a higher location such as the vent port at the gravity fill (for trailers that have a gravity fill). This has been previously suggested on this forum . . . maybe even somewhere in this 8 page 120 post thread . Grand Design is now also considering this, for trailers with gravity fill provision.

Rob