Solution to water Loss While Traveling

[Yoda]

I had this on the other site, but will rebuild the process here. The water tanks on our units are long and flat and not very tall. They are susceptible to surging. This causes water to push out the vent pipe and sometimes creating a siphoning situation. In some test drives up hills and around corners I was able to loose over 1/3 of my fresh water tank. A simple solution is to just to install a 3/4" SharkBite valve. https://www.homedepot.com/p/SharkBit...00LF/202270643 However if used improperly it can cause tank failure. It must be open during filling and use of water from tank. So you need to remember to open it. I tried this st first but found my memory lacking so I wanted a system that automatically vented.

SharkBite fittings com in many sizes and typed and most places like Home Depot, Lowes, Ace ,etc carry them. They are a push on fitting and work well. Just remember to pick up the removal tool when you get the fittings. https://www.homedepot.com/p/SharkBit...712A/100638161 they also have this in 1/2 inch.

So in the attached photos what I did was run 3/4 pex from the original vent line forward and installed a 3/4 air/vac above the tank elevation at my docking station. I do have a low point drain and keep it open when filling. So once I have filled my water tank I can use at will without having to remember to open the valve and risk damage to the tank. It also vents the tank during normal travel.


Using 2 - 90 degree bends I connected to the vent line and ran outboard to the frame. Zip ties work well to secure the line.
Edit: A tee could be used here instead of the 90 on the tank vent. This would allow one to add a drain valve below the T at this location to remove any water from the vent line after traveling depending where your low point is on you piping runs. In my case is was forward of this point as I had these 90's so high.



I then ran forward through the suspension.



At a convenient point I installed a 3/4 T and a 3/4 ball valve https://www.homedepot.com/p/SharkBit...-202721929-_-N This ball valve allowed me to install the 90 PVC fitting (white plastic part) The line running forward goes to the plastic tub below the docking station. (edit) This drain valve must be at a low point in the system so water can be drained after traveling allowing the vent line to work..



I drilled a hole in the corner of the tub and used a 90 fitting to go upwards inside.



Inside the docking station area I routed the pipe upwards to the highest point I could to be sure I was above the top of the fresh water tank. For the air/vac to work it must be above the tank.



The 3/4" air/vac (green top) allows air to enter or leave the system, but closes if water gets to it. I picked mine up at an irrigation supply store for about $15. It has an insect screen in it too. These are commonly used on garden drip systems. This is an expensive example of what I used https://www.dripdepot.com/item/netaf...yABEgJj9vD_BwE Home depot may carry them too

Well I hope this helps others.

Edit:
When you fill your tank, let it equalize - stop draining before closing the low point/vent valve. If you overfill (easy to do) and close the valve early water can get to the air/vac closing it and not allowing the system to work as intended. In addition when you arrive at your camp and have leveled your trailer, open the vent drain valve and let any water that has entered during travel to drain out so the tank can again equalize. Catch this water for use if needed. You can leave the valve open until you get ready to travel. If you get something called a vacuum breaker, be sure it works both ways as some only work one way. Air needs to move freely in and out. In fact if you wish you can just run the pipe to the ceiling of the pass through (should be well above the top of the tank) and leave the air/vac off, but you may see water in the area after traveling which is why I used the air/vac to prevent my leak detectors from going off. I would put a bug screen over it if you leave it open.

Questions?......there will be a quiz later

On edit I found a cheaper 3/4" air/vac https://www.dripdepot.com/item/kinet...yABEgJ5bfD_BwE
and
https://www.amazon.com/Drip-Depot-Ki.../dp/B00THEJLB4
There are probably others out there.

[howson]

Well I hope this helps others. Questions?......there will be a quiz later

This will definitely help those that carry water with them. (Can't do it in my 315RLTS for any significant distance--not enough payload!)

Would the system below (assuming there's space to actually install it) work as an alternative? (I've already got the space utilized near the Nautilus panel for drain lines for the DW's washing machine.)

[Yoda]

This will definitely help those that carry water with them. (Can't do it in my 315RLTS for any significant distance--not enough payload!)

Would the system below (assuming there's space to actually install it) work as an alternative? (I've already got the space utilized near the Nautilus panel for drain lines for the DW's washing machine.)

It might - I know there is a little room above the tank, so if you can get the vent ball high enough. It needs to be above the static water tank level when full. The other solution is go to the other side opposite the Nautilus panel or to the front cargo area like above a propane tank.

[RickLight]

I found your post earlier and proceeded to do this in steps, but it's not quite working right.

When I first discovered I was losing water I jammed a wine cork into the overflow for travel. Simple, effective but awkward.

Then I added a valve but I extended the tube to be up by the sewer drain. (273MK) This seemed to work for a while, but then one longer stay I noticed the tank still showed as full after several showers. But when I opened the valve water came out, for quite a bit. I had tried opening it when we first parked, but water came out and I figured we were slightly tipped or over full or something. Finally there was a giant sucking sound and the tank read under 1/3rd. Obviously the tank was under negative pressure. That needed to stop!

So I added your extension into the pass through with a vacuum breaker. After a few days on the next trip I checked and I still had water coming out when I opened the overflow. I removed the vacuum breaker (did I do that right?) and nothing happened. Then I BLEW into the tube pushing some water back up the pipe, and was rewarded with that big sucking sound.

Your tubing looks much longer than mine. Have you seen any signs of this issue?

Any thoughts?

[Country Campers]

It is imperative that the valve be opened when filling. When water is seen exiting stop filling and let the tank equalize , no more water exiting the over flow pipe. Then you can close the valve that you installed. Upon arrival you should open the valve so the tank again will stabilize and you will not have any negative pressure or the pump will not have to "suck" water from the tank. Another note is if you gain or lose altitude while traveling , this will have an effect on the tank pressure as well.

Brian

[Yoda]

No I have not had any issues like you mention. Spent a long weekend dry camping and went through 2/3 of a tank. The tank will need to pull the water back out of the vent when in use, but this is a small amount. Having the vent or even a second vent as howson shows could help. However I don't think the bit of suction on the tank is going to hurt. When you open the drain valve there is a huge sucking sound after a few minutes then a lot of gurgling - correct?.

To solve the issue, when you get set up, open the drain valve and drain the water that is in the vent line. This should be only a few cups worth or a few seconds of draining, unless you overfilled then there could be more. If water is critical, use a clean bucket to catch what you drain and use that water for something else. When I fill and water starts flowing out the overflow - I shut of and let the water flow stop before closing the valve. Now you say you have a vacuum breaker at the end - does it work both ways? Can you blow and suck air through it easily. If not you have the wrong unit (some are one way) . You need an air/vac unit, one that allows air to move in both directions (you can blow and suck air through it) , but closes if water gets to it wants out as might occur due to sloshing. That water will stay in the vent line until it is either sucked back into the tank or drained. Its also important the Air /Vac be well above the tank. If water gets to it it can hold the ball closed. This could occur if the tank is overfilled.

Now it is important that the drain valve be at the low point in the line too, otherwise you will have water still in the line preventing venting like you appear to have.

Can you post some pictures of your set up. and location of your drain valve and vacuum breaker. It would help greatly.

[RickLight]

More info:
I went so far as to physically remove my anti-syphon fitting when I was first noticing trouble. I may leave if off if not much water comes out.
It's about 6 feet from my overflow to the pass through up section. It's not a lot of water, but the tank couldn't pull it back in until I helped.

Photos attached

[Yoda]

More info:
I went so far as to physically remove my anti-syphon fitting when I was first noticing trouble. I may leave if off if not much water comes out.
It's about 6 feet from my overflow to the pass through up section. It's not a lot of water, but the tank couldn't pull it back in until I helped.

Photos attached

Rick

Looks like a good install. If you took your anti-syphon device off, cover the end of the pipe with some screen to prevent bugs from getting in (that's why I chose the air/vac I used as it has a built in bug screen). I think when you get set up at the new camp site that draining what water is in the line will solve your issue. You may need to slightly adjust the drain valve to make sure it is the low point. In the one photo looking to the rear you have a high point ahead of the low point drain. Could leave water in the line where you attached to the vent. With the slack you can adjust while draining. Please post back on how it is working. Its good to get feedback as that adds information others can use.

Nice job
Thanks
Keith

[Guest]

This will definitely help those that carry water with them. (Can't do it in my 315RLTS for any significant distance--not enough payload!)

Would the system below (assuming there's space to actually install it) work as an alternative? (I've already got the space utilized near the Nautilus panel for drain lines for the DW's washing machine.)

Howard,

I'm thinking about drilling a hole in the floor where you placed the anti syphon valve and connect a line to the unused vent next to the gravity fill. This vent is accessible under my cabinet on the Imagine. So no anti syphon would be used in this design where it would drain down once the overflow valve is opened. One thing that I do not like is the open vent to the side of the rig. I've seen some gravity fills with a small door on them that would prevent rain from entering the vent when traveling. Another way of solving the vent/rain issue while traveling, would be to run the line above the gravity fill vent where any expansion would exit the vent and no rain could enter the system from travel.


Jim

[RickLight]

Keith, Thanks for the positive comments, I'm no plumber!

The T is the low point in the horizontal run, and of course the valve is well below that. But I'll double check.

I think my issue is that I still haven't broken the siphon. As I now believe the siphon effect is strong enough to nearly drain the tank, seemingly without any air getting inside. The big mystery has always been how so much water gets out from an overflow. My theory of the moment is that the tank is so flat and so flexible that it just doesn't take much to nearly collapse it. Certainly the pump has enough power and maybe the siphon does too. If the tank walls are so weak they can't pull up a cup of water in the overflow then that would explain all the problems. All the concern over the path and closure of the overflow may be irrelevant next to this simple process.

I may have to drop the chloroplast and deal with the original design defect. Sounds like Jim is on the same path.

[Yoda]

I thought I would update the thread. I have taken the ball out of my air/vac so in case I have a senior moment and not open the lower drain valve when filling, water will gush out giving me warning to turn off the water before damage occurs. The ball is in the bottom section that unscrews. It wold prevent water from coming out if I overfilled and left valve closed.



The green top is a bug screen

[TedS]

As for pulling a vacuum, pumps claim 6 to 8 foot lift. That's about 3 to 4 psi. The vent tube is around 1.5 feet long, that's about .8 psi. A water column of 2.3 feet