Water Overflow Tube

[Colorado]

Originally Posted by Johnynorthland

Hey Colorado, where’d ya get those fancy shutoffs ?

I wanna say, Lowe’s. Amazon probably has them too

[dbahn]

Originally Posted by dbahn

Since the check valve's only purpose is to allow air IN if water is pumped out then one check valve should be sufficient, and the check valve might be the most expensive component of the system (around $15). If I put the check valve upstream of the rubber plug it would let air in during negative pressure in the tank (from the pump) but prevent water from exiting the tube during positive pressure in the tank. One of the valves I looked at had a release pressure of under 1 psi, which is quite low.

I think if you added one "in" and one "out" then one of them would defeat the purpose of not allowing water to exit the tank during MH movement, the so called "siphoning" effect created with movement.

A pin hole somewhere in the system would allow equlibration of air pressure from temperature or altitude changes (which occur slowly) even if it let water out a few drops at time. (Ironically, if you're nearly out of water and your plugs are put in when it's cold, with an increase in temperature or altitude the air expansion could blow one plug out, which doesn't happen when the tank is full.)

Follow-up to above:

1. I measured the pressure required to blow out one of the rubber plugs. It's somewhere between 5 and 10 psi, so it's well below the 40 to 50 psi pressure of a water fill or the pressure that could be created by air expansion in the tank from temperature or altitude.

2. This photo shows the very simple connection to any one of the three vent tubes from the fresh water tank. The plug would just "blow out" with over-pressurization of the tank, and the one way check valve will allow air to enter the system if a vacuum is created by running the pump with rubber stoppers blocking the tubes, serving as a safety valve if you forgot to remove the stopper during use of the water pump. I'll just use a little silicon adhesive to the T tube connections, since it should not be exposed to high pressures and leakage would not cause a problem "upstream" even if it occurred.

So in practice, all you really need to do is remove the single visible plug when filling, and replace before traveling, but if you turn on the pump and forget to remove the plug the tank will just suck air in from the check valve. I'm guessing that the materials added up to around $20 and I consider it simple to install and use and is also essentially foolproof.

I may put a little stainless steel mesh in the end of the tube where the stopper goes if we continue to remove the stopper for filling, which we don't really have to do anyway, so if end up leaving the stopper in except for filling bugs have no access to the tank in the first place.

[Johnynorthland]

Nice!

What it that elbow you used? What size is it?
You mind giving me a material list? Please?

[dbahn]

Originally Posted by Johnynorthland

Nice!

What it that elbow you used? What size is it?
You mind giving me a material list? Please?

It's the plastic version of a "1/2 inch Shark bite 90 degree connector", which is less expensive than the brass version.

That connects to the existing 1/2" vent tube on one end and a new piece of 1/2 PEX tube on the other.

Towards the end of the PEX tube, you insert a T connector which attaches to the check valve and a continuation of the PEX tubing, held in place by a standard pipe clamp with screws. I used a little clear PE tubing because I had it around, but you can put a short piece of PEX tube there instead.

Those parts are labelled here in yellow in the original diagram. I plan to simply glue the T connector in place with silicon adhesive rather than PEX clamps. It doesn't matter if it leaks a little bit and there should not be any significant pressure build up before the cork would be popped off, i.e the connections are not critical.

Here's the check valve I used, and make sure the flow arrows point down into the PEX tubing in order to let air IN:
https://www.amazon.com/dp/B07C16XM4R...roduct_details

[Johnynorthland]

Thanks, I didn’t think that 1/2 shark bite would fit on the drain tube. Mine is garden hose type material, it’s soft and playable. Is yours that way too?

[SmokerBill]

You all make things so complicated. I been shoving a Sharpie marker into my overflow tube to plug it up for the last 10 years and it's never fallen out in 40k miles of travel. I remove it when filling the tanks, and insert it when the tanks are filled.

Works for me. LOL

[dbahn]

Originally Posted by Johnynorthland

Thanks, I didn’t think that 1/2 shark bite would fit on the drain tube. Mine is garden hose type material, it’s soft and playable. Is yours that way too?

Yes, it's the flexible tubing but it does fit into the shark bite with a little effort and seems to hold together for the purpose involved. If it were a critical connection I would consider joining it to PEX then joining the PEX to the vent drain, but realistically if the present connection fails you are just back where you started and can revise the connection.

If you really don't trust the check valve you can always use an additional one to make it nearly fail-safe, but I just don't see a need for that. There's also no reason you couldn't fit this to all three vent tubes, but I just think that's a waste of time and money.

[SmokerBill]

No check valve is necessary on my rig. There's a separate air intake tube at the fill port to allow air in as the tank empties. And the fill port cap doesn't make an airtight fit, so that's another path for air to replace the outgoing water.

[dbahn]

Originally Posted by SmokerBill

You all make things so complicated. I been shoving a Sharpie marker into my overflow tube to plug it up for the last 10 years and it's never fallen out in 40k miles of travel. I remove it when filling the tanks, and insert it when the tanks are filled.

Works for me. LOL

Don't you need three Sharpies? We have three overflow tubes.

Don't you have to crawl under the RV to do that?

What if you forget to remove the Sharpie and start drawing water from the FW tank by using the pump?

The only reason this is more "complicated" is to make it more "foolproof". We've been using just the PEX tube extension attached to the underside of the wall and a rubber stopper to prevent overflow, and that also works fine on its own (as long as you remember to remove it).

I like the convenience of having the end of the tube easily visible to you while you're filling, then sticking the stopper in when you're done.

[dbahn]

Originally Posted by SmokerBill

No check valve is necessary on my rig. There's a separate air intake tube at the fill port to allow air in as the tank empties. And the fill port cap doesn't make an airtight fit, so that's another path for air to replace the outgoing water.

It must be that not every version has that air intake tube. Otherwise you wouldn't hear stories of people collapsing their FW tank by installing shut-off valves on the vent tubes.

[SmokerBill]

Nah, I just have to get down on my knees to remove the Sharpie and then re-insert it when the tanks are filled. I have two fresh water tanks, and they originally were vented separately. I connected the overflow tubes with a TEE fitting so there's only a single overflow now.

I always keep the overflow plugged when using the fresh water from the tanks. As I said in my previous post, there's an air intake tube at my fill port that allows air into the tanks as the water is depleted. I guess mine was designed differently than yours.

[SmokerBill]

Originally Posted by dbahn

It must be that not every version has that air intake tube. Otherwise you wouldn't hear stories of people collapsing their FW tank by installing shut-off valves on the vent tubes.

Thanks for the clarification dbahn. I've only had the one trailer, and I assumed they would all have an air intake tube at the fill port. I guess using the fill ports without an air intake saved Jayco a dollar or two per RV in manufacturing costs. LOL

[dbahn]

Originally Posted by SmokerBill

Thanks for the clarification dbahn. I've only had the one trailer, and I assumed they would all have an air intake tube at the fill port. I guess using the fill ports without an air intake saved Jayco a dollar or two per RV in manufacturing costs. LOL

Not only that, my understanding is that they started fitting the tanks with three vent tubes instead of one because people would fill their tanks without a pressure regulator, and a single vent tube was simply not adequate to prevent rapid pressure build up in the system.

As I've mentioned previously, the simple engineering solution it to vent the tanks well above the top of the FW tank, even if it has to go inside the wall, but they've probably saved more that a dollar or two by not doing that simple fix.

We've definitely run into fill stations that have pressures well above the 40 to 50 psi level, in which case the pressure regulator is usually essential.

[SmokerBill]

Yeah, I guess mine is different. I use a hose with the fitting cut off its end to fill the tanks, so in addition to the open overflow tube, there's also plenty of space for air to escape back up through the fill port, past the hose when it's filling. It's a pretty simple design. And I fill my tanks slowly, so I guess that makes a difference in my situation.