water tank siphoning?

wwleowner · 03-31-2009, 09:40 PM

Hey guys, I had an issue last year that I wonder if anyone has had similar issues. On one of my trips I had to fill my water tank before I left; I filled it until the vent tube started to drain; Upon my arrival at the camp about 250 miles away my monitoring system indicated approx. a half tank of water; the monitor showed full when I left; I have been wondering if maybe the water was siphoned by the vent tube; I checked for leaks at the tank and all over the camper but there was no sign of a leak; By the way, we have a 26tbss and truly enjoy it; Any words of wisdom will certainly be appreciated;
Thanks,
wwleowner

turbopuppy · 04-01-2009, 02:36 AM

250 miles is about a 4 hour drive+/-. If it was real hot maybe it evaporated out the vent after it stopped sloshing out the vent tube on those left hand turns!

NWJeeper · 04-01-2009, 11:10 AM

Quote:

Originally Posted by wwleowner

Hey guys, I had an issue last year that I wonder if anyone has had similar issues. On one of my trips I had to fill my water tank before I left; I filled it until the vent tube started to drain; Upon my arrival at the camp about 250 miles away my monitoring system indicated approx. a half tank of water; the monitor showed full when I left; I have been wondering if maybe the water was siphoned by the vent tube; I checked for leaks at the tank and all over the camper but there was no sign of a leak; By the way, we have a 26tbss and truly enjoy it; Any words of wisdom will certainly be appreciated;
Thanks,
wwleowner

You aren't loosing that much water due to evaporation, it is in fact siphoning. We ran into the same issue on our new Georgetown on our maiden voyage. We had topped off the tank at one stop knowing that we would be without hookups for a couple of nights. Imagine my shock to get to our destination on that first night and find that we only had about 1/3 tank of water! It's seems that FR has done an abysmal job of venting the water tanks and they don't seem to understand that they should be vented to an location higher than the tank.

When we got back into a town I measured the vent tube and found it to be 3/4". I went to the hardware store and bought a female hose end, one of the washer screens that fits into the end of a female hose connection and a plastic hose shut off valve. I installed the female hose end on the drain tube, inserted the screen washer into it (to keep the bugs out) and then screwed on the valve. Now I open the valve to fill the tank and then close it when the tank is full so that I don't loose water on the trip. When we get where we are going I can open the valve again so that the tank vents again.

out4stlhed · 04-01-2009, 12:05 PM

I have had a similar experience. I have found that if you fill the tank too quickly air becomes traped in the tank and the vent tube will let water escape making you think that the tank is full, however, it is not always filled to capacity. The sensors will read full at that time but if you turn the fill water off for a while let the stand the air will eventually vent. Begin filling again at a slower rate and there should be no problem.

I have been using a slow fill rate and have had no problems in quite a while.

dharri770 · 04-01-2009, 09:50 PM

I too have filled up and when I arrive at my destination 3hrs later, I only had half a tank of water. I had planned on adding a valve to my drain line like was mentioned, but maybe I will give the slow fill a try first.

NWJeeper · 04-02-2009, 10:20 AM

Quote:

Originally Posted by dharri770

I too have filled up and when I arrive at my destination 3hrs later, I only had half a tank of water. I had planned on adding a valve to my drain line like was mentioned, but maybe I will give the slow fill a try first.

Think about it logically, how can filling the tank slower prevent your water from running off? I don't get this theory. While in AZ on our trip I filled the tank full and then pulled the motorhome out of it's spot and up the street to hook up our Toad. As the rig was sitting leaning towards the passenger side the water started pouring out the vent hose. In my rig the tank is located above the propane tank and there is a plastic blank off plate there with two inspection covers there. I have removed both so that I can visually inspect the level of the tank because I don't trust the sensors. I have filled with full force and watched to make sure that it is full so the speed at which you fill has nothing to do with it. It's simple physics. FR has a really dumb design for venting their tanks.

out4stlhed · 04-02-2009, 11:49 AM

If you choose to park on a hill with the vent downhill I imagine that you will loose water. Here is an idea, don't park with the vent downhill.

Filling the tank slowly allows air in the tank to escape as you are filling I don't see why that is so hard to understand.

cfsoistman · 04-02-2009, 12:27 PM

Quote:

Originally Posted by NWJeeper

Think about it logically, how can filling the tank slower prevent your water from running off? I don't get this theory. While in AZ on our trip I filled the tank full and then pulled the motorhome out of it's spot and up the street to hook up our Toad. As the rig was sitting leaning towards the passenger side the water started pouring out the vent hose. In my rig the tank is located above the propane tank and there is a plastic blank off plate there with two inspection covers there. I have removed both so that I can visually inspect the level of the tank because I don't trust the sensors. I have filled with full force and watched to make sure that it is full so the speed at which you fill has nothing to do with it. It's simple physics. FR has a really dumb design for venting their tanks.

I think what's trying to be conveyed is that water is being seen coming out the vent pipe when filling up so the RV owner stops filling the tank. The tank is not full but water is being pushed out the vent pipe from the water entering through the hose and the air in the tank. I've had this happen on every Pop-Up, trailer and the motorhome I've owned. Once I see it I turn the hose down so the flow into the tank is lessened. The air escapes and the water stays in the tank. I'm not saying that anyone is turning off the water before the tank is full, this is just my observation of what has been posted.

I never fill my fresh water tank completely, when the light says it's full I stop. I haven't had any problems losing water, maybe I've been lucky?

NWJeeper · 04-02-2009, 08:19 PM

Quote:

Originally Posted by out4stlhed

If you choose to park on a hill with the vent downhill I imagine that you will loose water. Here is an idea, don't park with the vent downhill.

Filling the tank slowly allows air in the tank to escape as you are filling I don't see why that is so hard to understand.

out4stlhed: Read the post again, I didn't say I parked on a hill with the vent down hill. I was parked on flat and level when I filled the tank. When I pulled out on the street where the PASSENGER side of the rig was a little low the water started running out of the vent! This is a faulty design to the water vent systems on FR rigs. Mine was hanging about 3' below the tank. In what universe I ask will that not be condusive to siphoning?

This is not a new subject and I have seen it come up time and again on other forum groups concerning the FR rigs, and it is not just one type, it is most all of them, the trailers, 5rs and motorhomes.

Filling the tank slower will not stop the guy from loosing 1/2 tank of water over a 250 mile drive. Nor will air in that tank keep him from being able to get it more than 1/2 full....

Now is that so hard to understand????

out4stlhed · 04-05-2009, 08:23 PM

You know what you are absolutely correct. Any fool can see the that there is no way that there could be another explanation, especially since a senior member makes a statement, it must be ture.

You know, i have tried to contribute to this site based upon my experience.

I did ask one question with one miss statement in it and two senior members made me feel like a a total idiot. I think that i have had enough of this site. Thanks for the good infirmation that i got, bit i am done.

wwleowner · 04-05-2009, 08:42 PM

Well fellows, I didnt mean to stir up any controversy. I just wondered if anyone had seen anything like this before. Personally I really appreciate all of your input. It never hurts to ask your fellow campers for advice. I think my path is clear according to all of your posts. I think I will install a valve on the overflow/vent tube and fill the tank slowly. As a matter of fact I intend to make sure that there is no water flow to my house when I fill the tank and observe my water meter to ensure that I get close to 50 gallons of water. I want to thank you all for your input!
WWLEOWNER

The_Stuff · 08-10-2010, 06:25 PM

you think the vent thing is bad? mine the elbow off the side of the tank at the top drains right on the ground! I want to put a hose on it and bring it up to the vent but i will get the trailer situated in a perm spot first.

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