This fresh tank siphoning is killing me

TonyCO · 06-16-2019, 09:46 AM

Long story short. We filled up at home for a big trip to Moab. I notice water leaking out of the over flow drains the entire trip. Get to the site and gauge says 1/3 tank. No doubt we had less than half the tank because we ran it dry and had all sorts of room in the gray and black tanks.

It’s a Rocky Mountain Edition. Sure I live on the Front Range of the Rocky Mountains and I like the color scheme better than the regular style, but the main reason I went with it is because of the 80 gallon fresh tank. I email Jayco and they tell me it’s something that happens. Take it back to the dealer so they can add more hose inside the tank to stop the siphoning. Ok, but I’m not giving it to those guys until the winter. Just home from work this morning and getting ready to head out to Black Canyon and Blue Mesa. I’m not in a rush so I figure let me screw around with this thing. It has two overflow tubes so I stick a valve on each. Then I dig out my old water meter I purchased years ago for my last trailer (never took it out of the package). I start filling and at 38 gallons it starts leaking out of both overflow valves. I keep going and at 58 gallons it’s coming out the fill tube. I shut everything down and let it settle. I keep the overflow valves closed and slowly begin to fill. Immediately starts coming out the fill tube again. So it looks like I have a little less than 58 gallons in my 80 gallon tank.

Anything else I can do? Any suggestions? Thanks for letting me VENT!

billjmck · 06-16-2019, 10:48 AM

Put little 1/4 turn valves on the end of hoses. Turn them off "after" fill up and don't forget to open them when you get to campsite. Fix them later the way you want.

JimD · 06-16-2019, 10:51 AM

Jayco's wonderful way of filling your tank. On my 2017 Greyhawk I would lose 1/3 of my 40 gals before I reached my boondocking site. Finally discovered the siphoning problem with these units.

This is a known problem with Jayco and has been discussed on this forum many times. I ended up putting valves on my 2 overflow hoses plus my vent hose. Many other people have done similar things with good success. I fill the tank and then close all 3 valves. When I arrive and am set up I will open only the vent valve. Works like a champ.

This method works as long as you remember to open the vent valve. I once forgot to open it and the tank built quite a vacuum and for some reason the level never came off full. When I finally opened the vent, you could hear the air being sucked in and the gauge then showed a lower value. Funny that the pump never slowed the water flow to the sinks.

As far as capacity, what is stated includes what is held in your water heater. I noticed this on the Jayco specs because my unit has a tankless water heater (groan) and my spec shows 6 gallons less than identical units with standard water heaters.

Wish I had a 80 gallon tank!

**JFlightRisk** · 06-16-2019, 12:25 PM

https://www.jaycoowners.com/forums/m...cture6497.html
I added valves to the overflow hoses, also. Same as above, open them to fill the tanks, then close. Once on site, open them to use the pump. Don't be surprised to see some water come out once they're opened. I've noticed the tanks bulge slightly when full, and relieve themselves a little until they stabilize some.

TonyCO · 06-16-2019, 05:53 PM

Ok, thanks. I totally agree with the valves and in fact that is what I did this morning. I secured a valve on each overflow tube. So with the six gallon water heater I have about 64 gallons out of 80. We just cruised in to Curecanti. I opened both new overflow valves and they are running hard. So the siphon is still holding true. Can I use the water pump with those valves closed? Or will it suck the plastic tank inside out? Ugh. What a pain.

RAurand · 06-16-2019, 07:04 PM

Don't these tanks have a air vent along side the water fill port?
When I am filling my tank, I can feel the air coming out this vent.
If the over flow valves are kept closed after filling, and the water pump is turned on, wouldn't the air vent prevent the pump from sucking (compressing) the tank

Robbbyr · 06-16-2019, 07:36 PM

Quote:

Originally Posted by RAurand

Don't these tanks have a air vent along side the water fill port?
When I am filling my tank, I can feel the air coming out this vent.
If the over flow valves are kept closed after filling, and the water pump is turned on, wouldn't the air vent prevent the pump from sucking (compressing) the tank

What you are describing sounds like a gravity fill arrangement which does have a vent near the fill port (example picture below). Unfortunately those of us that have (had) the siphoning issue do not have a gravity fill port, we only can fill our tanks by using the City water connection and aligning our panel valves to send the water to the tank. Since our setups can cause full city water pressure to be directed to the tank Jayco installed several overflow lines on the tank to keep us from over-pressurizing and rupturing our tanks. Those same overflow lines serve as vent lines to admit air back into the tank when you are drawing water out of the tank since we don't have the high-mounted vent like a unit with a traditional gravity fill connection does.

There was a Seneca owner who purchased a used unit which, unbeknownst to the new owner, had shutoff valves installed in the overflow/vent lines. He unknowingly used the water pump for a while and collapsed his tank. I believe he was able to remove the tank and re-expand it back to shape and salvage his tank. Valves work, but one must be vigilant in their use.

**JFlightRisk** · 06-16-2019, 07:39 PM

We have the twin FW tanks, and only the front one is vented to the water fill fitting, like the one pictured above. The rear one is connected to the front by way of an equalizing hose. So yes, you need to open the valves to use the pump. You probably can get away with leaving them closed for a short while, using the pump until the overflows slow down. The pump will cause suction on the rear tank if the overflow valves are left closed.

RetiredOne · 06-16-2019, 08:48 PM

Quote:

Since our setups can cause full city water pressure to be directed to the tank Jayco installed several overflow lines on the tank to keep us from over-pressurizing and rupturing our tanks. Those same overflow lines serve as vent lines to admit air back into the tank when you are drawing water out of the tank since we don't have the high-mounted vent like a unit with a traditional gravity fill connection does.

OK, I understand the need for the multiple overflow/vent tubes (my unit has 3) so you don't over pressure the tank when using city fill.

What I don't get is why they continue to siphon. If they are vent or overflow tubes, aren't they mounted in the TOP of the tank. I can see some sloshing when moving, but how does the water continue to siphon when stopped, if these are in the top of the tank? Once the level drops an inch, it should stop. Right?

Do they have hoses internally in the tank that run down on the inside? This would be the only way it would continue to siphon, but if the ends of those hoses are in the water, they wouldn't vent???

Like the top ports in this tank:

**JFlightRisk** · 06-16-2019, 08:56 PM

Excellent question! I've wondered the same, but can't see/tell how far into the tank they are. Maybe someday I'll drop the rear tank, just to take a look. You're right, they should be just at the top, and siphoning should stop once the water's not touching the hose. Goes back to siphoning gas out of cars. It only took a second for the flow to stop once out of the gas.

DRE · 06-16-2019, 09:46 PM

Quote:

Originally Posted by Robbbyr

What you are describing sounds like a gravity fill arrangement which does have a vent near the fill port (example picture below). Unfortunately those of us that have (had) the siphoning issue do not have a gravity fill port, we only can fill our tanks by using the City water connection and aligning our panel valves to send the water to the tank. Since our setups can cause full city water pressure to be directed to the tank Jayco installed several overflow lines on the tank to keep us from over-pressurizing and rupturing our tanks. Those same overflow lines serve as vent lines to admit air back into the tank when you are drawing water out of the tank since we don't have the high-mounted vent like a unit with a traditional gravity fill connection does.

There was a Seneca owner who purchased a used unit which, unbeknownst to the new owner, had shutoff valves installed in the overflow/vent lines. He unknowingly used the water pump for a while and collapsed his tank. I believe he was able to remove the tank and re-expand it back to shape and salvage his tank. Valves work, but one must be vigilant in their use.

I use the city water connection and direct the valves to fill the FW tank. When full and it starts to overflow I shut off water to the city water connection, and redirect my valves for dry camping and the overflow stops immediately.

RetiredOne · 06-16-2019, 10:32 PM

Quote:

Originally Posted by JFlightRisk

Excellent question! I've wondered the same, but can't see/tell how far into the tank they are. Maybe someday I'll drop the rear tank, just to take a look. You're right, they should be just at the top, and siphoning should stop once the water's not touching the hose. Goes back to siphoning gas out of cars. It only took a second for the flow to stop once out of the gas.

Great... I see I'm not the only crazy one here...

I've seen these tanks, and they just have threaded ports on the top that you can screw a barb fitting into. I never saw any internal hose that went down into the tank. So, in my mind, once the water gets below that port, the siphon has to stop, but people here claim they can lose a half a tank of water... How??

The gas siphoning is exactly what I'm referencing (sucked in a bit of gas in my youth, LOL), the second the end of the hose comes out of the liquid, the siphon stops.

**JFlightRisk** · 06-16-2019, 10:41 PM

I GOT IT!!! All the water tanks have been installed upside down in the frame!!

Whew, am I glad that's finally figured out.

jd99336 · 06-17-2019, 04:13 AM

I asked the same question on another thread a while back. Siphoning doesn't make sense, as a siphon must remain submerged in the water and once water drops below the inlet, the siphon is broken. Granted each vent tube can maintain it's own siphon as long as it is lower than the other tubes, but ANY air getting into the tube on the tank end will break the siphon (just physics...right).

The best explanation is the very shallow depth of the tanks allowing for a siphon of the top part of the tank, but it should not be extending below those unless Jayco plumbed excess tubing into the vents that drops further into the tank.

As such, I cannot explain how it is dropping to 1/3 of a tank (which essentially is anything below 2/3 right?), unless just the sloshing from driving is doing it. For instance if your vents are in the front of the tank, the water would likely rush forward, draining out during the full braking manuever.

The other odd thing is that a siphon will not work long without a vent in the tank allowing air to replace the water being siphoned out (think holding the tip of a straw in your soda and blocking the top and the soda stays in the straw).

While we describe this thing as a siphon, I don't really think that is what is at play. Rather I think shallow tanks, and poor vent placement is simply allow water to slosh out.

I am going to try extending my vents some distance away from the tanks to get them above the top of the tank, but there is no convenient way to do that.

Riich · 06-17-2019, 06:02 AM

I bought two little rubber stoppers at the hardware store and stick them in once the water starts to overflow. I can do this by simply reaching between the two tires on the left side. This has made a huge difference, once I get to the camp site and use a little water I remove the stoppers and nothing is lost anymore. I am on my 5th and final day of camping as I write this and I have all kinds of water left, it is showing 2/3 full yet. I'm tickled.

Robbbyr · 06-17-2019, 08:22 AM

I am a Seneca owner who lived with the issue for a few years until I fabricated and installed an air break (air gap) manifold that solved my issue. Before I installed it I could lose 1/3 - 1/2 of my 80 gallon tank while driving. On several occasions I even had people pull up beside me at traffic lights to tell me I was "leaking something". I don't know if it would stop and then restart when I would accelerate, causing the water to shift towards the rear where my 3 overflows come off the top. The tank has no baffles so that might be part of it.

My tank is in a compartment and can be easily seen by removing a cover, and I am fairly certain there are no dip tubes from the vent/overflow connections down into the tank. Whether the tank was partially collapsing when siphoning was my suspicion but I never did remove the cover in the compartment while it was doing it to verify. But I can say when my tank is full the middle bulges up several inches and when empty it sags inward the same amount. So there is flex in the poly tank to begin with.

Jayco did publish a repair document advising owners or dealers (if it was a warranty complaint) to route one of the vent/overflow hoses up and then back down creating an air gap or break. I would have had to bring it up through the floor into my bedroom which I didn't wish to do. So as part of my hot water recirculation project I built and installed my air break manifold. That was the end of my siphoning woes.

RetiredOne · 06-17-2019, 08:45 AM

Quote:

Originally Posted by JFlightRisk

I GOT IT!!! All the water tanks have been installed upside down in the frame!!

Whew, am I glad that's finally figured out.

Ahhh ha.... You solved it!!!!

Neo1130 · 06-17-2019, 03:05 PM

Anyone know what size hose this is so I can purchase the 1/4 turn valves? I have the issue too of course and with a bad back, broken ribs, and bad hips, etc... It's hard to climb under there and I just want to be prepared for one trip down below.

TonyCO · 06-17-2019, 04:10 PM

Peterson Molding 18958CW Drain Valve https://www.amazon.com/dp/B007HRQHNI..._o9acDb0X7K95P

Just put these on before this trip. Perfect fit on my trailer.

us71na · 06-17-2019, 07:08 PM

Quote:

Originally Posted by TonyCO

I email Jayco and they tell me it’s something that happens. Take it back to the dealer so they can add more hose inside the tank to stop the siphoning.

Anything else I can do? Any suggestions? Thanks for letting me VENT!

Who ever the person was at Jayco that told you to take it back to the dealer to add more tubing inside the tank was sleeping in High School physics when siphons were discussed. This is absolutely the wrong approach. Adding more tubing inside the tank will do nothing.

I am not familiar with your trailer, but there is a very simple and inexpensive solution you could try. The way to stop siphoning is to introduce air at the high point of the siphoning tube. You may be able to do this yourself. Find the highest point of the overflow tube and insert a plastic tee so the straight through part follows the current path for the water. On the side outlet of the tee, add a piece of tubing and run it to any point at least a foot or more above the highest portion of the tank(s). Make sure that if water comes out from a pressurized city water fill that it will spill on the ground and not into your trailer. Leave the end of this tube open to the air. The tank will overflow when necessary, but as soon as you stop filling or shortly thereafter the siphon should stop. The water in the hanging down portion of the overflow tube will suck air into the tube thereby breaking the siphon. Note that if the tube coming from the tank is some distance from the top of the tank, you are not siphoning, but simply draining the tank down to the level of that outlet. You may need to raise the overflow tube so it goes right up against the floor of the trailer (or higher if possible) to be higher than the top of the tank(s).

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