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Topic: Fresh Water Tank Leaks through vent pipe on turns

Posted By: bgarner540 on 01/02/13 11:52am

When I fill my fresh water tank on my motohome and drive straight or making turns or going up hill or down the water tank leaks water out the flow tube. Usually it empties out 2/3's of the tank. Is there away to stop this from happening? Any help or suggestions would greatly be appreciated. Thanks


Posted By: paulcardoza on 01/02/13 11:53am

I find it hard to believe that you lose 2/3 of your tank this way? It does not seem like that would even be possible!!!


Paul & Sandra
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Posted By: midnightsadie on 01/02/13 12:10pm

so he missed his figures a bit ,why make a big deal ,he realy would like ways to fix it. #1 see if you can get to the top of the tank from inside the rv? #2 if your not handy it,ll need the shop to remove seal the pipe to tank fiting. might even call the factory for help.


Posted By: wolfe10 on 01/02/13 12:14pm

Is the water coming out the VENT or the FILL?

And, yes, an improperly installed line can allow the tank to be siphoned down.


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Posted By: Archie Kravitz on 01/02/13 12:16pm

I've got the same problem on mine. The vent tube is stuck down into the top of the fresh tank and when it slops out when you turn it acts like a siphon( Like when you drained your kids inflatable swimming pool). I go from having 105 gallons down to 85 after siphoning. What I do is I bought a small spring hand clamp from Lowes and clamp it on before I travel. The only thing the over flow is used for is if your shut off don't shut of when filling.


Posted By: old guy on 01/02/13 12:27pm

don't think for a minute guys that it can't happen. I know for fact it does. it has happened to me. many times when I go hunting and go around the corners in the mountains I would look out the rear mirrors and see water shooting out the fill pipe. when I get to camp I notice the fresh water tank is at least one third empty. that is why I carry 5 gallon jugs with me just to fill the tank up again and if I use a lot of water for showers etc I will get more water to bring into camp.


Posted By: Bumpyroad on 01/02/13 01:05pm

mine would pour out a bit if that corner was low but to empty it that much you must be siphoning it out.
bumpy






Posted By: jetboater454 on 01/02/13 02:07pm

Lowes or home depot,get a rubber plug for the vent. My trailer came with a rubber cap for the vent. Never used it,it just lays behind the fill door.


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Posted By: dkreuzen on 01/02/13 03:22pm

See my post in iRV2 forum.
Click here


Dennis
2012 Monaco Knight 36PFT
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Posted By: Raymon on 01/02/13 03:28pm

I installed a 1/4-turn PVC ball valve on my vent tube to prevent siphoning. When filling the tank, I open the valve. When water starts flowing out of the overflow tube, I turn off the water, then turn off the ball valve. After using some of the water from the tank, I open the ball valve to prevent a vacuum from forming in the tank. Then if sitting still, I leave the ball valve open; if traveling, I may close the ball valve depending upon how much water is remaining in the tank. I have done this modification on 3 RV's. Works for me.

Ray


Posted By: BobR on 01/02/13 03:45pm

Simple solution is to loop the vent hose/pipe higher than the tank to resolve the problem.


Posted By: Dolph on 01/02/13 08:11pm

Had a 2000 Dolphin that lost about 1/2 the fresh water while traveling. Water was coming out the overflow pipes on both sides. The cure was easy. Traded it in on an 08 Pace Arrow.


Posted By: Lantley on 01/02/13 08:19pm

Raymon wrote:

I installed a 1/4-turn PVC ball valve on my vent tube to prevent siphoning. When filling the tank, I open the valve. When water starts flowing out of the overflow tube, I turn off the water, then turn off the ball valve. After using some of the water from the tank, I open the ball valve to prevent a vacuum from forming in the tank. Then if sitting still, I leave the ball valve open; if traveling, I may close the ball valve depending upon how much water is remaining in the tank. I have done this modification on 3 RV's. Works for me.

Ray

X2
Install valve on the drain line/vent line or both to keep water from escaping.
Keep valves closed when traveling.


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Posted By: zman-az on 01/03/13 05:26pm

What is happening is when you fill the tank the sides of the tank expand due to the weight of the water. When you go around a corner and water is pushed into the overflow outlet (which is most likely side mounted rather than on the top) it will syphon out the water and pull the sides of the tank back into their original state. Once that point has been met there will be no more syphoning. You can actually watch this happen by just over filling the tank and not even move.

To correct this issue on my RV I routed the overflow line above the tank, added a tee at this level and routed a vent line up and the drain line down so the water would not be forced out my new vent line. Have not had a problem since I did the mod. Other option is a cap installed while driving.






Posted By: 2bzy2c on 01/03/13 09:53pm

Dolph wrote:

Had a 2000 Dolphin that lost about 1/2 the fresh water while traveling. Water was coming out the overflow pipes on both sides. The cure was easy. Traded it in on an 08 Pace Arrow.


Good one![emoticon]


My advice is worth exactly what you paid for it.


Posted By: bgarner540 on 01/03/13 05:35pm

Thanks, for the many good suggestions.


Posted By: Bumpyroad on 01/04/13 05:12am

zman-az wrote:

What is happening is when you fill the tank the sides of the tank expand due to the weight of the water. When you go around a corner and water is pushed into the overflow outlet (which is most likely side mounted rather than on the top) it will syphon out the water and pull the sides of the tank back into their original state. Once that point has been met there will be no more syphoning. You can actually watch this happen by just over filling the tank and not even move.

To correct this issue on my RV I routed the overflow line above the tank, added a tee at this level and routed a vent line up and the drain line down so the water would not be forced out my new vent line. Have not had a problem since I did the mod. Other option is a cap installed while driving.


I was thinking of this remedy myself but then wondered about having an open vent to potentially filthy/dusty/dirty air being drawn in when the tank volume lessened.
bumpy


Posted By: zman-az on 01/04/13 09:05am

Bumpyroad wrote:


I was thinking of this remedy myself but then wondered about having an open vent to potentially filthy/dusty/dirty air being drawn in when the tank volume lessened.
bumpy


You can get a cheap fuel filter to use. The overflow line does not have a filter so you are still exposed. Put a cap or valve on will also do the trick.


Posted By: wolfe10 on 01/04/13 02:26pm

zman-az wrote:



To correct this issue on my RV I routed the overflow line above the tank, added a tee at this level and routed a vent line up and the drain line down so the water would not be forced out my new vent line. Have not had a problem since I did the mod. Other option is a cap installed while driving.


What you made was a homemade anti-siphon valve. VERY common in boats where the engine and much of the plumbing is below waterline.


Posted By: stuplich on 01/04/13 08:37pm

jetboater454 wrote:

Lowes or home depot,get a rubber plug for the vent. My trailer came with a rubber cap for the vent. Never used it,it just lays behind the fill door.


I would think if you completely PLUG the vent you will prevent makeup air from entering as you pump water out with the fresh water pump.

A completely plugged vent could result in the water not flowing, (or could collapse the water tank).


Posted By: teddyu on 01/05/13 06:37am

A simple filter I made for my tank after raising the vent/overflow line was a 1" foam brush with the wooden handle removed, slipped over the line end and tie-wrapped in place. No bugs and still acts as the vent/overflow. JM2ยข...


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Posted By: dkreuzen on 01/05/13 07:57am

stuplich wrote:

jetboater454 wrote:

Lowes or home depot,get a rubber plug for the vent. My trailer came with a rubber cap for the vent. Never used it,it just lays behind the fill door.


I would think if you completely PLUG the vent you will prevent makeup air from entering as you pump water out with the fresh water pump.

A completely plugged vent could result in the water not flowing, (or could collapse the water tank).


That is absolutely correct. With the vent plugged and water being pumped out there is a very good possibility of damaging the tank. Just modify the vent so it has enough rise.


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