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

[Neal]

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.

 

[RandyB]

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.

 

[Richpatty]

Neal, what manual fill are you referring to?

 

[Neal]

Neal, what manual fill are you referring to?

At the wet bay. Turning the lever to fill fresh instead of autofill.

 

[Richpatty]

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.

 

[Crockdar]

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.

 

[Buly]

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