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Exboston · 09-13-2014, 04:47 PM

I have a Winnebago vista 30T which loses fresh water out fresh water tank via the overflow tube. It seems like there might be a vacuum pulling the water out of the tank. Does anyone else have this problem?

Thank you for the help

DieselTech39 · 09-13-2014, 04:56 PM

Glad you're aboard. Sorry I can't help with your water overflow problem. I'm sure others will be along to help. Best of luck on a solution. Enjoy your adventures and be safe.

BFlinn181 · 09-13-2014, 05:22 PM

It's not a vacuum, but a syphon. Water sloshes out the overflow hose, and if the down segment of the hose is longer than the length of the hose dipping into the tank, it will continue to pull water out of the tank until the hose in the tank sucks air. You can try to pull the hose dipping into the tank out a bit so it doesn't pull so much water, or, at the high point of the loop poke a small hole in the hose to break the syphon effect.

jergeod · 09-13-2014, 06:44 PM

On my Georgetown they used a hose you would use for a pool filter 1 1/2". What I did was reduced the size down to 3/8 hose and mounted it to the under floor of the coach and now I don't loose my water.

gatorb8 · 09-14-2014, 06:22 AM

Quote:

Originally Posted by BFlinn181

It's not a vacuum, but a syphon. Water sloshes out the overflow hose, and if the down segment of the hose is longer than the length of the hose dipping into the tank, it will continue to pull water out of the tank until the hose in the tank sucks air. You can try to pull the hose dipping into the tank out a bit so it doesn't pull so much water, or, at the high point of the loop poke a small hole in the hose to break the syphon effect.

X2!
I've had to install syphon break in 3 rv's
Sometimes a small hole on the high point of the overflow tube will work fine

hogdriver · 09-14-2014, 06:34 AM

My RV has an anti siphon valve. I think they are cheap.

Finally Time · 09-14-2014, 03:25 PM

Had the same problem with my 27N. The dealer rerouted the overflow up then down forming an "upside-down p trap." No more siphoning.

Old Scout · 09-14-2014, 03:42 PM

Usually, the siphon effect only occurs when the the tank is totally full. Only time I worry about a totally full tank is dry camping so I installed a manual shutoff valve on the end of the overflow tube--only close it while on the way to dry camping. If your tank doesnt have a secondary overflow line--you have to make sure you open the valve once you arrive at camp--......

alilly · 09-14-2014, 06:56 PM

Quote:

Originally Posted by jergeod

On my Georgetown they used a hose you would use for a pool filter 1 1/2". What I did was reduced the size down to 3/8 hose and mounted it to the under floor of the coach and now I don't loose my water.

Our previous MH had a small overflow hose on the FW tank and if you didn't watch it the input water volume (even gravity fill) could exceed the overflow volume. The tank, mounted under the bed, would swell up and break one of the wooden cross braces under the bed. Second time this happened I figured it out.

I felt very lucky it just broke a brace, a ruptured tank would have been an expensive disaster.

VanDiemen23 · 09-14-2014, 08:17 PM

I actually had a siphon problem that sucked the tank to collapse. all that's needed to break the siphon is to take an air hose and blow back into the overflow.

jcullipher · 09-14-2014, 08:58 PM

I have a 2013 Thor Challenger 37DT that is doing the same thing. I have two vent hoses, both on passenger side of coach that will pull a full tank of water to one third in 50 miles driving time. It is currently in the shop for this and some other minor warranty issues, both solutions above have been discussed with my shop. A poor design for sure that needs to be corrected. If they cannot fix it, I will begin work on it myself.

BFlinn181 · 09-14-2014, 09:31 PM

Quote:

Originally Posted by jcullipher

I have a 2013 Thor Challenger 37DT that is doing the same thing. I have two vent hoses, both on passenger side of coach that will pull a full tank of water to one third in 50 miles driving time. It is currently in the shop for this and some other minor warranty issues, both solutions above have been discussed with my shop. A poor design for sure that needs to be corrected. If they cannot fix it, I will begin work on it myself.

I don't think it's a poor design, but poor execution. The shop workers and/or inspectors should know better to install a vent like that, it's been known for thousands of years!

Your vent probably looks like the one on the left, it should be like the one on the right:

jcullipher · 09-14-2014, 09:39 PM

Basically, yes, mine has an elbow in the top for the drop hose and I, like you think it needs to extend upwards several inches, with a loop. I talked to one guy with the sMe problem and setup, he used a hacksaw to cut a very shallow slice into the elbow , he said it broke the siphon. I wanted to try the loop first, IF I have enough vertical space and I am not sure about that. And thanks.

Gordon Dewald · 09-14-2014, 09:41 PM

Quote:

Originally Posted by Exboston

I have a Winnebago vista 30T which loses fresh water out fresh water tank via the overflow tube. It seems like there might be a vacuum pulling the water out of the tank. Does anyone else have this problem?

Thank you for the help

I dont know if this will apply. You did not say whether the tank runs until it is empty so I am assuming that after filling it runs for a bit.

I was speaking to Troy at Winnebago regarding installing an RO system to run the coach on. His concern was the "outlet" which he referred to as a vent was only 1/2 inch. His caution was that if one did not turn off the water when filling the tank there was the probability of ballooning the tank. Upon occasion they have experienced tanks that have ruptured due to the "overfilling".

If you are filling the tank to the top you may be causing the tank to expand. When you stop filling the tank will return to its original shape and continue to expell the extra water until it has returned to the original shape.