Tip How to stop your fresh tank from siphoning after an overfill

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Joined
Jul 27, 2019
Messages
3,903
Location
Midlothian, VA
RV Year
2017
RV Make
Newmar
RV Model
Ventana 4037
RV Length
40' 10"
TOW/TOAD
2017 Chevy Colorado
Fulltimer
No
Tonight I wanted to top off fresh just in case the water lines are frozen in the morning and I can't top off prior to heading to Quartzsite. This happened to me at Lake Powell when I waited for refill day and couldn't due to frozen lines which they said never happens! My SeeLevel showed 100% but I wondered how much further I could go. I shined my iPhone flashlight on the fresh tank to watch the level and I was about to stop when that sound occurred, yep, overflow. The interesting thing is it wouldn't stop! I watched the SeeLevel go down to 96% which is really coming off of full at the top of the sensor strip is not really the top of the tank, it's centered vertically.

I shut off the water, closed the manual fill, still draining. I decided to turn off the city water and open the manual fill valve and then open an unused connected on my y-valve on the city water. Bingo! This air source allowed the flow to stop immediately.

So if you experience this you want to create a VENT at the fill side by opening the manual fill and disconnecting the city water hose or opening a y-valve to form a vent.
 
Joined
Nov 15, 2019
Messages
254
Location
Portage, MI
RV Year
2017
RV Make
Newmar
RV Model
Ventana LE 4037
RV Length
40' 11"
TOW/TOAD
2021 Chevy Trailblazer
Many Newmar owners (and other brands too I suppose) have repiped the vent. This involves running a loop up several inches higher than current. The least that some have done is drill a small vent hole in the tubing at the top of the loop. Others have included a tee at the top of the loop with the side branch facing up. Attached to that up pointing branch is another tube to provide the anti-siphon vent. Remember that any hole is an entry point for contamination into your fresh water tank.
 
Joined
Nov 2, 2019
Messages
48
Location
Wesley Chapel, NC
RV Year
2017
RV Make
Newmar
RV Model
Ventana 4310
RV Length
44
TOW/TOAD
2007 CR-V
Neal, what manual fill are you referring to?
 
Joined
Jul 27, 2019
Messages
3,903
Location
Midlothian, VA
RV Year
2017
RV Make
Newmar
RV Model
Ventana 4037
RV Length
40' 10"
TOW/TOAD
2017 Chevy Colorado
Fulltimer
No
Joined
Nov 2, 2019
Messages
48
Location
Wesley Chapel, NC
RV Year
2017
RV Make
Newmar
RV Model
Ventana 4310
RV Length
44
TOW/TOAD
2007 CR-V
Ah! ok. My mind had a picture of a pour-in spout into the tank (which I have heard some folks adding)

As far as breaking that siphon action, before I changed the overflow to stop this problem (below pic) I used to carry a short length plastic tube that I would slide into the overflow (as it was pouring out) and then blow in the other end. This would force air into the overflow and break the siphon... Not pretty, but effective.
ED5949C2-0D06-43FA-8F66-E98FB03D49D3.jpeg
 
Joined
Jan 17, 2020
Messages
5
RV Year
2019
RV Make
Newmar
RV Model
Dutch Star 4369
RV Length
44
TOW/TOAD
2019 F-150 w/M&G braking
Tonight I wanted to top off fresh just in case the water lines are frozen in the morning and I can't top off prior to heading to Quartzsite. This happened to me at Lake Powell when I waited for refill day and couldn't due to frozen lines which they said never happens! My SeeLevel showed 100% but I wondered how much further I could go. I shined my iPhone flashlight on the fresh tank to watch the level and I was about to stop when that sound occurred, yep, overflow. The interesting thing is it wouldn't stop! I watched the SeeLevel go down to 96% which is really coming off of full at the top of the sensor strip is not really the top of the tank, it's centered vertically.

I shut off the water, closed the manual fill, still draining. I decided to turn off the city water and open the manual fill valve and then open an unused connected on my y-valve on the city water. Bingo! This air source allowed the flow to stop immediately.

So if you experience this you want to create a VENT at the fill side by opening the manual fill and disconnecting the city water hose or opening a y-valve to form a vent.
Can’t wait to ty this, thanks.
 
Joined
Nov 3, 2019
Messages
460
Location
TGO Titusville FL
RV Year
2015
RV Make
Newmar
RV Model
Dutchstar 4369
RV Length
43
TOW/TOAD
2014 Honda CRV
I did something like you RichPatty, but few of us had a different problem at the balloon fiesta this year. Everybody arrived with fresh water tanks full. We were diverted to a side area to disconnect the toads. It was very slanted and the coaches were leaning way too much to the right. Fresh water started pouring and it run until we moved out of there. Some of us lost 1/3 of the water we had.
So, I have to redo my system to be also spill proof
 

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