Sewer Flush Explosion

[ScottandBrenda]

Ok, not really an explosion, just a flooded dinette slide. The pipes that are involved with the sewer flush on our 2006 3500RL broke or came disconnected. I traced the lines back from the flush to the spot where they go UP INTO THE WALL and then back down again. I suspect that the lines are hooked to some RVAA code vent or something, because that's where the water was pouring down and nothing else seemed to up there. To get to it, I'd have to remove the wall in our kitchen or the shower unit. I wanted to do neither. I cut the lines and installed two fittings to simply tie them together in plain site. Sewer flush works perfectly now.

Anybody else have this problem?

[bsmeaton]

Scott,

I'm not sure that was the best fix. The tank flush has a backflow preventer valve that probably is what failed. It is a vacuum break type and yes - it is required - but it is also critical. It prevents backwash from the blank tank from entering your flush hose as well as the CG potable water system. In Fact, if your modification was done low enough, the black tank will actually start syphoning out through the tank flush inlet in your panel and flood your basement with crap - so to speak. There are no valves other than the one you just bypassed that will prevent this!!! If you have the older Montana, it will discharge outside on the ground.

The valve has to be serviceable, so somewhere there should be access to it. I would swiftly pursue repair .

[ScottandBrenda]

Thanks Brad! [[I've added edits to this post in these brackets.]]

Yep, I've been camping/RVing for about 45 years now, and I did think of that - even though I didn't mention it. I also found other posts on here about the same subject.

From a hydraulic standpoint, [[it seems to me that]] back flow is only possible under one circumstance. If someone used the sewer flush with the black water valve closed, it would pressurize the system. One of two things would happen. There would be a failure of some sort in the system and there would be a leak, perhaps significant, or, when the water was shut off AND the black water level was high enough to reach the sewer flush outlet, the pressure could cause a small back flow until the pressure was alleviated. However, the following points: 1. the only way there can be a back flow is if the waste level in the tank is about half-full. I've dropped the belly of our unit and visually inspected where the spray head enters the tank on the passenger side of the coach. If the waste level is below the spray head, no back flow is possible, except air. The sewer flush is used after the tank is emptied or nearly so, so the waste level being that high is never the case. 2. The holes on the spray head are pretty small, offering a significant resistance to water or waste flow. Hook a hose up to your sewer flush and blow in it and you'll see just how hard it is. There's a lot of pressure in that system when it's being charged with water. Further, if waste did back flow, it would have to be completely particulate free or it would rapidly clog the spray head. 3. The inlet/outlet connection in the lines is about 3 feet above the level of the spray head on the black water tank. There would have to be significant head pressure to get any back flow through the spray head, and up the line. [[I'm focusing ONLY on the flush process - the normal use process is a different story and there are issues]]

That being said, I agree that it never hurts to be safe - even if it's way overboard, [[turns out I'm wrong - it's not way overboard, and it's a required part of the system]] and I'm installing a check/breaker valve in the lines where I made the repair. It's easy enough to do and it complies, for the most part, with Keystone's original design. I also recommend to anyone who reads this post that they do the same in order to comply with RV Codes and Standards (or whatever it's called) [[RVAA]] and to keep the insurance companies happy [[and to keep you, your family, and our fellow campers safe as well]]. I believe it's totally unnecessary, it's a bit like swatting a fly with a sledge hammer, but what the heck [[wrong again - I didn't think the issue through before I posted]]. The advantage is that now it's in a place where if/when it fails again, I can get to the dang thing easily [[it needs to be higher than the maximum black water level - in other words, as high as possible, like in the original location]]. (I talked to an RV manufacturer about this - the rep I spoke to agreed that it is not a necessary thing, but an overboard safety measure. Two RV techs at two different dealerships also agreed.)[[see post below for more info on this]]

Good idea though, to install a new check/breaker valve. I hereby modify my original post.

[[I could have deleted this whole thing, but a little lively discussion is a good thing and affords an opportunity to learn more about what is being discussed]]

[bsmeaton]

Scott,

There is nothing hydraulic about it. Bacteria migrates, even upstream, in potable water systems. Everytime you turn off the water to the flush the water pressure goes static. Each time, bacteria is allowed to migrate from the spray nozzle up into the hose. As you describe, that nozzle is periodically submerged in raw sewage!! The air gap in the backflow prevention valve is designed to stop that. Without it, your hose up stream of the valve becomes contaminated, the hose you use to flush becomes contaminated, and OUR campground potable water supply becomes contaminated. By rights, just by bypassing the valve for your emergency, you would be required to sanitize your feed hose and black tank flush line if you did repairs commercially.

This is not new science. Your lawn irrigation system has either a vacuum break valve or pressure reducing double check backflow preventor to prevent lawn contaminants from entering the city potalble system. Your commercial building systems as well as industrial water and fire protection water systems all have backflow prevention from the potable supply. I'm not sure what makes you think your above grade human solids waste tank would be immune from this proven phenomina!

I appreciate your years of RVing. I also believe the rep you spoke to should be fired from his position, and the RV techs you talked to are typical for RV techs that know little but talk lots. Thank goodness there are mightier minds empowered by the RVAA and federal government that watch out for our foolish attitudes.

I strive to leave a clean and sanitary campsite as I pull away and would ask others to do the same by keeping the "overboard safety measures" in good condition and operable.

Nothing personal -

[Mudchief]

Scott, Like Brad stated above, look for a square plastic cover about 6 inches square with 4 screws holding it in place. In my unit it is in one of the kitchen cabinets.

[LonnieB]

I'll be the first to admit I have by-passed failed safety devices designed to protect me from myself that were installed on various vehicles, equipment, and other items. In most cases it was done so I could continue operation until repairs could be made.
In this case though, where the safety device is designed to protect not only the operator, but the rest of the general public, I agree with Brad, it should be repaired the way it was designed, before it is used again.
Nothing personal here either.

[RKassl]

Does anyone know where this valve is located on a 2955RL?

Thanks

[EagleRunner]

Bob,
On the 2955RL open the vanity doors (the sink next to the shower). You will find two pipes rising from the floor to the valve.

Tom

[mtnhntr]

Bob and Tom,
On my late 2005 2955RL the vacuum breaker is reached by opening the cabinent doors above the pantry in the kitchen. In there you will find a 6"x6" covered opening in the forward wall. Remove the cover and look in. You will see the vacuum breaker. It is very difficult to work on as I can only get one hand in there. My vacuum breaker needs replacing and while I got it off, I am having a hard time tightening the fittings - ended up leaking on me and spraying down the inside of the walls.
Ken

[RKassl]

So what does this vacuum break look like? Why would one what to replace the valve, and how d you know when it's bad?

Thanks

[CRUZIN 2]

This is what it looks like. I had to replace mine also, when it gets bad it leaks.

[dsprik]

Brad, where is this on the 3400? Someone here a while back mentioned this location once, but since we're on this thread...

[ScottandBrenda]

As I said above, that valve needs to be there.

We have a motto when we camp: Always leave the site cleaner than when you found it, including campfire ashes if possible, and always leave a few pieces of wood for someone else. Further, I have informed campers who are obviously very new that they should not hook up water hoses to the public water faucets in the campgrounds if they don't have check valves on them due to water contamination issues. Full hookups are, of course, not subject to this limitation. For all I know it might just be the campgrounds we've visited as well and other campgrounds are different.

That being said, as I said in an earlier post, I certainly am going to replace the check valve and make sure that it is as high as possible above the level of the toilet in our unit. I was focused on the flush process. However, when the unit is in normal use, if the black water tank gets full above the level of the spray nozzle in the tank, there are issues. If the black water tank, God forbid, gets full to the level of the toilet, there are hydraulic issues as well. That's why I said above that I recommended that anyone who reads these posts install the valve after the emergency repair.

Also, I called the techs back a little while ago, and elaborated on the problem and issues, and one agreed that the valve should be reinstalled after he understood the problem more thoroughly (I guess?). Further, after I read an email that I received I became aware that the manufacturer rep admitted that he was mainly public relations, and that his knowledge of the construction of the camper was limited. The other tech continues to insist that he's "done this on several units and there haven't been any problems".

At any rate, I repeat my earlier statement that I modify my original post, and that I am definitely NOT saying that the valve should be left out. I do think, however, that I will replace that valve first thing if and when we buy a new Montana. That dripping wet dinette carpet is just not something that we enjoy. Thank God it was flooded with freshwater and not "something else". [[Edit: this was only the sixth or seventh time we've used the unit - only 2 months out of warranty]]

In fact, I'm putting two valves in AND installing a video camera to watch it at all times. Kidding. Great discussion! Learning is a good thing. Thanks!

Scott

[bsmeaton]

Dave,

I believe it is up behind the shower. The access panel is in the pantry. I haven't checked myself but I'm going to now. I was not aware they would fail that often. There should also be a one page description and drawing of the flush system in your manual packet.

I did find a another spring loaded sewer vent that terminates in the void around the garden tub (serves the gray tank). It is behind the right hand inspection panel. I found it right after we took delivery while tightening fittings. The vent was actually laying on the floor because they forgot to put it back on after pressure testing (I assume).

[dsprik]

Thanks, Brad! I'll check that out. You're PDI guy actually did a pressure test??? Not sure if ours did, but sounds like a good idea on a PDI...

[CRUZIN 2]

Scott

We received a replacement for our vacuum breaker at (Lakeview RV Supply,Inc.) phone #512-261-8000 parts #1000

[EagleRunner]

Ken,
Just goes to show that a 2005 2955rl is not necessarily the same as every other 2005 2955rl. It depends where the unit sits at which time during assembly as to where things are installed anbd how. Things change throughout the year. I have that same panel opening in my pantry too, but it provides access only to the shower valve. I wondered how difficult it would be to replace that shower valve when the time came. I agree, not much manuevering room in there. I think I will keep my Monty. The location of that vacuum breaker on my rig is a whole lot easier to get to!!!

Tom

[bsmeaton]

Dave - 'fraid my PDI was pretty "low tech".

I was thinking maybe they pressure tested at the factory and left the vent off..............or maybe they left the vent off because they forgot when they came back from lunch...............or maybe they left the vent off because the assembler lost the directions on how to build a Montana..................or maybe they left the vent off because they figured it would be pressure tested at the PDI.............I'm just not sure. Anyway, I put it back on .

Also, when you reach inside that pantry inspection hole be sure and have the pocket door closed. Embarrased myself when I put the cover back on and mumbled there was nothing in there only to find out my flashlight was shining on the door.

[bncinwv]

That is two threads now talking about a pocket door. What the heck is a pocket door????
Bingo

[dsprik]

Brad, I found that vent cap by the tub. Mine was on but not tight. I screwed it on tight - hope that didn't defeat the spring action on that cap???

Also, had a "duh" moment... I found a wood rough cut piece of paneling screwed over a rough cut hole in my upper pantry. I took it off, only to find myself staring right at the sliding bedroom door that I had in the "open" position. I thought, "Well, that was a stupid place to accidentally make a hole - then a shabby way of patching it up." I screwed it back on to cover this jagged hole.

I pulled all of my wife's stuff out of the very bottom shelves, figuring that had to be the level of the vacuum valve. I had no access panel anywhere in site. Getting ready to go on here and post that I had a malformed 3400 with no access panel, when the realization slowly started to sink in... "Close" the bedroom door, pull that "rough patch job" back off that back of the pantry... Too late to wake up the wife tonight... but I will probably see that infamous valve in the morning.

Did I mention I had a college education??? I may be educated way beyond my intelligence...