no fresh water tank overflow 2018 Flagstaff 27BHWS

[babalu7420]

No problem filling our gravity feed fresh water tank full. The only indication that it is coming full is the gurgling sound heard from the fill port & when water starts to spew back out the fill port. There is a screened air vent beside the fill port that I can feel air being pushed out of the tank when filling, but no overflow tube under the unit as had on previous TT units.
Wondering if anybody else experiences this or if its normal operation ?

[Scrapper]

Sometimes if you try filling the fw tank too fast the displaced air cannot come out of the overflow tube fast enough. It can be caused by a kink or twist in the tube.

[babalu7420]

Originally Posted by Scrapper

Sometimes if you try filling the fw tank too fast the displaced air cannot come out of the overflow tube fast enough. It can be caused by a kink or twist in the tube.

Do you know for fact if this 2018 Flagstaff 27bhws has a fresh water tank overflow line ?

[Mr. Dan]

Originally Posted by babalu7420

Do you know for fact if this 2018 Flagstaff 27bhws has a fresh water tank overflow line ?

Good question. My Wildcat has no overflow line although some retired electricians might say all units do.

[doc73]

Our previous gray wolf had the screened part for the over flow but it was just a dud. The back side was filled with silicone and no hose. Had a short piece of oex that came right off the tank and onto the ground for the overflow.

[Scrapper]

Originally Posted by babalu7420

Do you know for fact if this 2018 Flagstaff 27bhws has a fresh water tank overflow line ?

All tanks must have a way for the displaced air to escape. If not then the tank will fill very slowly, not fill at all, or could possibly push the fill hose off the fitting or rupture the hose or tank.

[rockfordroo]

My Mini Lite only has the small vent next to the fill port.



No proof, but I suspect overflows are more prevalent on units that have pressurized (hose attaches) fill ports. They need to provide more relief capacity.

[Mr. Dan]

Originally Posted by Scrapper

All tanks must have a way for the displaced air to escape. If not then the tank will fill very slowly, not fill at all, or could possibly push the fill hose off the fitting or rupture the hose or tank.

A vent to displace air is not the same thing as an overflow line. Some units have both. Mine only has a vent (pictured above) - no overflow line.

[Adrian Gordon]

Originally Posted by Scrapper

All tanks must have a way for the displaced air to escape. If not then the tank will fill very slowly, not fill at all, or could possibly push the fill hose off the fitting or rupture the hose or tank.

They must also have a way for air to get in to displace the water that you pump out of the tank. Otherwise, you will collapse the tank.

[bigmurph]

This is a 2020 Flagstaff on the assembly line. One fill tube, one vent tube, and fresh tank to pump tube.

[Garrette]

There ate 2 FW fill systems that I am aware of. Pressurized fill and non-pressurized gravity fill.
The Pressurized design is found on the wet bay bulkhead that accepts a threaded hose connections. This requires an overflow.
The non-Pressurized design does not have a separate overflow. The overflow is at the fill. When FW tank is full, the water will simply back-out around the hose..The small screen vent is just an air vent to the FW tank.
The overflow pipe on Pressurized system is your vent.
A minor caution note.
On the non-Pressurized system it is possible to Pressurized your FE tank if you jam the hose on the fill port. Not likely, but possible.
On Pressurized systems some overflow piping is found to ne too short thus setting up a siphon action while driving. When you get to the CG with 2/3 water gone, you know. ,

[Cabinfever97]

Our old TT had just the vent on the side of fill. Our current TT has overflow under the camper. Both do the job of venting and overflow when full. I like the side vent better, does not loose as much water as the under hose does.

[5picker]

My Flagstaff 8529IKBS has only the vent line next to the fill port.
My brother's 528RKS Flagstaff was the same.

I have to fill it slowly as the port fill is much bigger than the vent size.
If you do not fill slowly, you will get an erroneous spew back, thinking the tank is full when it isn't.

Also once full, sometimes my vent line gets water in it and filling the next time is even slower. I have fashioned a short piece of clear tubing that I hold against the vent hole/screen and blow into forcing the water out of the vent line allowing a bit faster fill.

I'm not sure why some folks want to fill their tank in 10 seconds?
As mentioned, jamming the hose in the fill port and turning on full blast can cause ballooning of the tank, buckling of the brackets that hold the tank and heaving of the floor. I have seen all three.

I don't fill mine at a rate any faster than the size of the vent can allow air to escape. I also use a inline garden hose water meter. I know at a glance how much I've put in and how much more to go. (if the tank was empty)

[markb422]

Originally Posted by Adrian Gordon

They must also have a way for air to get in to displace the water that you pump out of the tank. Otherwise, you will collapse the tank.

Our MH has a pressurized fill port, with a check valve, and two overflow lines that come off the top of the FW tank and go down through the floor. The overflows are 1/2" pex and, when new, open at the bottom. It makes sense the overflows also serve as vents but I was concerned that they are open to bugs getting in the tank so I installed duck bill checks on both overflow lines to prevent this. It also would make sense that if the system is closed the pump could collapse the tank the tank like you wrote. But I have not had any indication that is happening with my tank. When the pump creates suction wouldn't the check valve at the fill port unseat to allow air in before the tank would collapse.

[rockfordroo]

Originally Posted by markb422

Our MH has a pressurized fill port, with a check valve, and two overflow lines that come off the top of the FW tank and go down through the floor. The overflows are 1/2" pex and, when new, open at the bottom. It makes sense the overflows also serve as vents but I was concerned that they are open to bugs getting in the tank so I installed duck bill checks on both overflow lines to prevent this. It also would make sense that if the system is closed the pump could collapse the tank the tank like you wrote. But I have not had any indication that is happening with my tank. When the pump creates suction wouldn't the check valve at the fill port unseat to allow air in before the tank would collapse.

You might think so, but if it takes just 0.5 psi to open the check valve, and let's say you have a 4' x 6' tank, that's 48" in x 72" in x 0.5 pounds/sq in = 1728 pounds of pressure, and on both the top and bottom of the tank. Certainly enough to collapse the tank.

[babalu7420]

Originally Posted by babalu7420

No problem filling our gravity feed fresh water tank full. The only indication that it is coming full is the gurgling sound heard from the fill port & when water starts to spew back out the fill port. There is a screened air vent beside the fill port that I can feel air being pushed out of the tank when filling, but no overflow tube under the unit as had on previous TT units.
Wondering if anybody else experiences this or if its normal operation ?

I would like to thank every ones response to my question !! I now understand the two differences of the fresh water fill & understand why there is not an overflow tube on my TT
THANKS