Overfilled fresh tank, then POP!

steelheadbluesman · 12-07-2010, 07:06 PM

Today, I needed to refill my fresh tank, so I switched my hose from "City" to "Fill", then got involved on my laptop, forgot all about the tank filling, and after awhile I heard a loud "POP!" just once, but it was really loud like a limb falling on my roof, only it was underneath

. So I raced back outside, shut off the water and opened the fresh water tank drain to relieve any pressure. The tank was absolutely full, and water was running out through a line that appears to be a 1/2 inch overflow that splits from the fill line on top of the tank, and then goes through the compartment floor. Question is: What might have made the load popping sound? I was afraid I had blown a line apart, or popped a fitting, and had those nightmare visions of a broken line in some mysterious dark corner under the floor, you know that feeling, right? So, I pressurized the system, first with the waterpump, then turned off the pump and opened the incoming city connection, looking and listening for leaks. It's been hours ago, and still no sign of any damage. I'm not even certain that the line I was looking at IS an overflow, I'll examine it more closely tomorrow. If it is, does anyone know if the overflow line might have had a cap on it that is designed to blow off under too-much pressure? Vent caps anywhere? Could the tank have made a loud noise from pressure? Is there a safety feature to handle this situation? I checked online schematics for my rig's plumbing, but couldn't find anything. Don't ya just hate strange sounds in your rig?? I'm stumped, and I'm still wondering if something got damaged....

Any thoughts will be appreciated.

**RickO** · 12-07-2010, 07:26 PM

Oh man.... I'll bet it took a toll on you when you heard that pop and made you immediately remember the tank filling.

Mine happened with the rinse hose left on in the black tank but we won't go into that.

Let's hope the loud pop was caused by the fresh water tank expanding and shifting around on it's holding straps.

Good luck...

Rick

**"007"** · 12-07-2010, 08:55 PM

I'll agree with Rick some tanks will be like sucked inward on top and bottom.
When you put in to much water and fast the tank will square off but if pressure really built up you could have split a seam.
A 1/2" over fill is kind of small, Newmar tanks have a 1 1/4" line out the top of them, they will fill fast and never will pop because of the size.

Luckiest Dre · 12-08-2010, 07:06 AM

I can't imagine there would be enough pressure from a hose that is filling the tank to burst much of anything. Even if there was, an open vent line would relieve that. I suspect the expanding tank theory is the best choice as an explanation.

Clay L · 12-08-2010, 09:23 AM

Quote:

Originally Posted by Luckiest Dre

I can't imagine there would be enough pressure from a hose that is filling the tank to burst much of anything. Even if there was, an open vent line would relieve that. I suspect the expanding tank theory is the best choice as an explanation.

Last spring in Palisade CO, a friend with a Georgetown motor home overfilled his water tank. The fill pressure was at least 65 psi - could have been more than 100 psi. The overflow vent hose appeared to be less than 1/2 inch as I recall.

The tank expanded enough to lift the floor, lift an interior wall, and break a metal brace over the top of the tank. There was quite a bit of damage to trim pieces, the wall, and the flooring. Total repair cost was over two thousand dollars.

Homes in Palisade have to have whole house water pressure regulators to prevent damage to plumbing. They are usually set at 65 psi.

wa8yxm · 12-08-2010, 09:36 AM

There may have been something.. Perhaps an insect nest, clogging the overflow.. It popped out.

jeanmike · 12-08-2010, 09:55 AM

I did the same thing. My Workhorse raised frame rail chassis has the fresh water tank between the rails and supported by a heavy steel bar that is attached to the frame rails by sliding into a slot attached to the frame rails. What happened is the overpressure caused the bar to be bent to the point that it slipped out of the slot on the frame rail. The whole coach shook and the noise was very loud. Mine is in the one main cross coach pass through storage bay just aft of the side entrance door. I reduced the amount of water in the tank and was able to push the bar back into the slot and tighten the hold down bolt. So far no leaks.

ArmyEOD · 12-08-2010, 11:22 AM

Lets hope it was just exspanding. Even at 1 lb PSI water pressure can add up in a hurry. Remember you can not compress water. I am guessing the flow rate in, was higher than your overflow out so the tank expanded and made that popping sound. When the tank is empty and the weather gets cold it may pop again when it goes back to the way it was. Just my 2 cents.

steelheadbluesman · 12-08-2010, 11:57 AM

I appreciate all your comments, it is always a great help to hear the thoughts of other experienced RVers.

I just got off the phone with an advisor at Winnebago, and here's what he said: The overflow is 1/2", so if your incoming line is a 5/8ths hose, with any pressure at all, the overflow won't handle it (go figure

), so it was an over-pressure issue. It may have expanded to the point where it "popped" the metal support pan under the tank (his first thought, and one he's heard before), or it may have split the tank, which he says happens ocasionally (but so far, no water anywhere), or it may have broken the baffle inside the tank, in which case there might be a leak from the top where the baffle piece is welded to the top panel of the tank. If the baffle is broken loose and cracked the tank top, a leak would only show up while driving with a full tank of water sloshing around, or if I recreate the situation by overfilling and over-pressurizing and then check for leaks at the top, which I will probably do. In the end, he figured it's most likely the baffle (says he's heard that one also.) If it broke loose from the top, but didn't crack the top panel, then I will have a compromised baffle, but no real damage, no leaking. Well, that's it for now. Today I plan to get a better look at the whole thing. I'll post any findings. Thanks again for your thoughts

Chuck 1935 · 12-13-2010, 06:17 AM

steelheadbluesman; If it broke loose from the top, but didn't crack the top panel, then I will have a compromised baffle, but no real damage, no leaking. Well, that's it for now. Today I plan to get a better look at the whole thing. I'll post any findings. Thanks again for your thoughts

[/QUOTE]

Did you ever get to the bottom of what happened ?

steelheadbluesman · 12-13-2010, 12:08 PM

So far no visible leaks, Chuck, although my water pump runs every once in a while for a short burst, which can be (though not necessarily) an indication of a small leak somewhere. But it's been raining hard non-stop and water keeps pooling under the rig, so I've been reluctant to completely root around under the frame to investigate any line leaks. (Might have to wait for a sunny Arizona day, you know?

) I'm pretty sure that IF the top was cracked, it would have sprayed or leaked water somewhere around the tank when it popped, but such was apparently not the case, as I was able to get my hands on three sides and the top of the tank, all over the mounting plate and bracket surfaces, and it was, and still is, bone dry all around the tank including the top surface (except for the back side, which is hidden up in the frame behind the slide.) That's it for now, thanks for asking

PS: When I asked the WB rep why the baffle might break under pressure, assuming equalized pressure everywhere in the tank, he said he didn't know, but he had known of it happening. Doesn't make sense to me.

Ray,IN · 12-13-2010, 01:18 PM

Keeping in mind you did not have a sealed connection between the fill hose and fresh water tank; the pressure applied to the tank from the hose could have been very high. PSI = pounds per square inch,that would be 65 PSI on a tank not designed for any pressure, 65 PSI can theoretically lift 104,000 lbs in a 40"X40" fire service rescue air bag Thus Clay L's experience.

Chuck 1935 · 12-13-2010, 01:36 PM

When I have switched from city to fill, I always wait until the water starts running out the overflow before shutting it off and have never had a problem with expanding the tank. That fill line from the city to fill valve is small and I would doubt that the volume of water would be enough to expand the tank. Maybe you had a touch of the vapors and thats what went POP?
I thought you were in Oregon ?

steelheadbluesman · 12-13-2010, 02:30 PM

You are right, Ray, water pressure can do unbelievable damage. I've been lifted ten feet in the air on the end of an inch-and-a-half fire hose when the nozzle pressure went from 110 to 125 psi! This tank problem occurs because of a "small" design error at Winnebago: The overflow line comes out of the top of the fresh tank and is a 1/2 inch line. Now, if your incoming line is a 5/8ths fresh water hose, like most of us use, there is a problem, because when the tank gets full, you have a 5/8" incoming water jet pressurized to 60 psi, that is trying to escape through a 1/2 line!

That's a big difference, so something has to give.

And you too are right, Chuck, I am in Oregon, up in the Cascades by Mt Hood, and it's certainly true that I could have had some kind of vapors, since I forgot I was filling my tank!

Whew, I'll bet I don't do that again....

Thanks to you both for input, I will eventually discover the end results, and if I have anything useful, I'll pass it along.