Water tank question

[Wandering5thwheelers]

Glad you figured it out. Both my 22MLE and 23LDE have two of those overflow tubes next to one another along side the dump valve. I assumed all of them have the same. Some people put a valve on the end so it can be closed once full. I thought about doing the same as I do lose water going down the road when it is full, which is only when we're boondocking. The risk there is that you forget to open it when filling and expand the tank with air trapped in it - and that can lead to bad things.

I have the 200MK TT and when I fill, I have the same issue as @IanHodson. Unfortunately for me, I also discovered that when tank was complete filled at a service centre about 1/2 hour drive from where I wanted to boondock, that every time I went uphill, water came out the blue hose, so in a pinch I placed a black felt tip marker in it, which sealed it. It worked! Now it’s part of my fill/drain/winterize checklist to remove it when filling. 2 years, no issues…fingers crossed. A $1.95 fix for me!��

[Riverbug]

I have the 200MK TT and when I fill, I have the same issue as @IanHodson. Unfortunately for me, I also discovered that when tank was complete filled at a service centre about 1/2 hour drive from where I wanted to boondock, that every time I went uphill, water came out the blue hose, so in a pinch I placed a black felt tip marker in it, which sealed it. It worked! Now it’s part of my fill/drain/winterize checklist to remove it when filling. 2 years, no issues…fingers crossed. A $1.95 fix for me!��

Funny you should say that. I noticed this weekend that after I filled the tank it ran out one of the blue tubes for a couple minutes then stopped. The gauge showed the tank was full. We drove 90 minutes to driveway surf at our niece's house. The tank was under 2/3 when we got there and if I had to guess, it wasn't more than 1/2 full based on how quickly we ran out of water. I guess it's time to do something about it before we do some real boondocking this summer.

[powerscol]

There are numerous threads and over at the GD teck place on how to solve this.
Here is my thread https://www.mygrandrv.com/forum/show...er+tank+siphon

[Mark_270BN]

Since the manual says "DO NOT OVERFILL" your water tank...likes it's death and destruction if you do...how do you get it just to full without overfilling it? Is there some room to work with when the gauge says full before it's actually full and I can turn off the water supply?

Also, today, when I went to fill it, it filled to 2/3 full and then water started coming out of one of the blue open-ended drain vales...so I stopped filling it.

Thanks.

[redfernclan]

Going for a shot in the dark here. We have a 23lde. Two tubes out of the fresh tank. The difference is we can fill the fresh water tank from the water hook up OR the gravity feed. We were also losing water en route to or camp. Put valves on the overflows. Since I fill up through the gravity feed, I should be able to keep the valves closed and get it completely full. Go where I need to and open the valves to ensure I don't damage stuff. The cap for the gravity fill is not air tight so I'm not sure if I even have to open the valves. More testing to come and I'll let you all know.

[COGrandDes]

I had this same issue on my other campers so I address it the same way including on my new Reflection 303RLS. It seems to be common on many of the brands based on the same tanks and venting assemblies that are used. I just install two sharkbite 90* valves on both of the lines and fix the problem for $20 and in about 30 sec. I keep the valves open when filling and then close both for transport. Once I get to my campsite and turn on the water pump, I open one of the two. Easy peasy! No water loss at all and I get the max gallons in the tank when I arrive at my destination.

[Dakota]

I filled my tank yesterday and watched water drain from the overfill tube. I don’t think it siphoned, but I’ve really never paid attention to it. I don’t think I’ve lost water while driving. Key word: think.

We are taking a longer trip next week. I need all the water the tank will hold. I’m going to stop and top off the tank when we get near our destination. I bought a meter to see how many gallons will go in. Hopefully not many, but it will be interesting to see if the siphoning issue is with all GD units or just some.

[COGrandDes]

I filled my tank yesterday and watched water drain from the overfill tube. I don’t think it siphoned, but I’ve really never paid attention to it. I don’t think I’ve lost water while driving. Key word: think.

We are taking a longer trip next week. I need all the water the tank will hold. I’m going to stop and top off the tank when we get near our destination. I bought a meter to see how many gallons will go in. Hopefully not many, but it will be interesting to see if the siphoning issue is with all GD units or just some.

Yeah we camp places where there is no place to refill once we arrive. We like the taste and feel of our softened water from the house. I leave with the tank max filled for each trip. I've done it that way for the last 18 years. Adding the shutoff valves ensures you arrive with what was loaded.

[redfernclan]

Just got back from our last "dry" trip. Filled the tank and left the valves that I had installed on the two vent tubes closed. I was able to do this because the 23lde has a gravity feed for the fresh water along with being able to fill it in the forward compartment. Filled it to overflowing but not pressurizing it. Drove the two hours to the coast over the pass and down the curvy mountain roads. Was very pleased to see a full tank when we got there. Opened one of the vavles on the vent tube and water started coming out so I knew I was clear full. Left it closed because again, the 23lde has a gravity feed so with the cap not sealing tight, I left the vent valves closed. I did also loosen the cap on the fill to ensure no issues. Took two showers, with did the dishes and used the toilet a lot. Came home after three nights with about five gallons left. MUCH happier with the new RV now that it would appear we have the fresh water issued solved. Sorry so wordy, just trying to help others out with what we have found.

[Wyowind]

I had this same issue on my other campers so I address it the same way including on my new Reflection 303RLS. It seems to be common on many of the brands based on the same tanks and venting assemblies that are used. I just install two sharkbite 90* valves on both of the lines and fix the problem for $20 and in about 30 sec. I keep the valves open when filling and then close both for transport. Once I get to my campsite and turn on the water pump, I open one of the two. Easy peasy! No water loss at all and I get the max gallons in the tank when I arrive at my destination.

I have the same issue of water loss on my 5th wheel. I read a few threads and was considering the simple fix of shutoff valves on my 2 overflow tubes. However, someone brought up the issue of pressure changes in the tanks when changing elevations. I see you live in Colorado and assume you have elevation changes from your home to campsites. I live in Wyoming and often travel from 6,000 ft to 10,000nft to camp or enroute to camp. Have you noticed any problems with sealing off the tanks and changing elevations, while camping?