Black Tank Flush System Diagram

[geo]

During a little research spawned by a different thread, I found the attached diagram. I thought I would share it with the Forum!

Note the comments - " . . .not be installed where venting of water from the device during normal functioning will cause damage." Hmmm, stuck up inside a wall, inaccessible, too big to get through the small hole drilled, behind the basement wall, and above the Transfer Switch. Naw, if the valve vented water, there's no damage there . . .

FYI, I did find one place (an RV dealer in New Castle, IN) who Internet sells these valves (Vacuum Breaker Model 571), and I'm looking for others. It says it must be installed 6" (15cm) higher than anything connected to the waste tank. So, I would imagine that this little valve is slightly higher than the toilet lid inside that wall!

I'm thinking maybe looking for a spring loaded check valve to put inline. Hank, what do you think?

Ron

[hankpage]

Ron, the function of that devise was not designed by Keystone and I am sure much testing went into it before being allowed to use on sanitary systems. I would strongly consider relocating it before using something not designed for that specific function. Once the smell of sewer gas or waste-water gets into a trailer it is next to impossible to remove. It is like many things today .... if it is installed and working correctly there should not be a problem. This is probably the reason for the disclaimer about it's location and possible leaks. I really can't say what I would do if I were faced with this problem. Hank

[ksfis43]

My check valve leaked the first time I used it. It is located under my bathroom sink.
After washing the black tank for about a minute I went inside the trailer to look down the toilet to see how it was spraying.
I had a huge mess in the bathroom, everything under the sink was soaked, toilet paper, towels rags, and the floor and bathmat were also soaking wet!, I ran out of that trailer so fast to shut the water off!
Luckily it was fresh water!
The dealer found that the valve was cracked when the factory installed it.
Works great now. I still go in and check it as soon as turn the Black flush water on, don't want that mess again.

[geo]

In the Alpine 3640, the vacuum/check valve is inside the wall between the "toilet closet" and the bedroom. Inside the toilet closet, there is a shallow linen cabinet on that wall. I have searched high and low in that cabinet trying to find an access panel to at least see that valve. Nothing. Unless I cut a hole in the cabinet, and then mount my own access panel . Now, on the bedroom side, SURPRISE! There is a 120VAC duplex socket in that wall . . . below the valve if indeed the valve is at least 6" higher than the top of the toilet.

So, let's add it up here . . . coming up from the basement . . . The Iota 50 Amp Transfer Switch . . . a 120VAC 15 amp breaker Duplex Socket . . . some RG-6 TV coax running about . . . and at the highest point, a Plastic Vacuum/Check Valve! Hmm, maybe I ought to start using WD-40 for flushing the black tank?

Hank, you are absolutely correct in pointing out the "change of design". As you can see in the diagram, not much of anywhere to relocate and still have it higher than the toilet. I have found a SharkBite spring loaded 1/2" check valve rated for 120 pounds pressure and for use on Pex. I'm thinking that this might be a "change of design" to "over-design". 120 pounds pressure is about 8 atmospheres, which translates into a fresh water column some 265 feet high! Surely that is better than six inches above the toilet lid. And, the spring keeps the valve closed when pressure (water) is not applied from the outside, thus trapping any gases inside the Pex piping. In theory, ought to work.

Ron

[JRTJH]

Ron, The spring valve you mention is designed to work in a liquid environment. I'd urge you to also assure it is "air tight" since what you're trying to keep out of the fresh water system is sewer gas as well as black waste fluid.

[geo]

JRTJH -

I agree. Should actually be fairly simple. Put a test guage on it and run it up to around 30 pounds. I can't foresee the black tank building more than one atmosphere pressure. Probably if it did, I would have more problems than a wet transfer switch!

Ron

[hankpage]

Looking at your floor-plan and what you have described. If the electric outlet you mention is in the bedroom wall ... disconnect from shore power and remove the cover plate and outlet you may be able to sneak a peek into that wall from there. Most trailers have some form of access panel to plumbing components. You may want to consider making one on the bedroom side of the wall once you locate where the valve is. JM2¢ again, Hank

[JRTJH]

Our trailer didn't come with a black tank flush system, I went to CampingWorld and bought one off the rack. It isn't connected to the fresh water system at all. In fact, it is a hose connection, hose, one way valve and a rinse head.

I realize that for convenience, so there is only one water hose connection at the side of the RV, the black tank flush system can be connected to the fresh water supply and then "isolated" with an antisiphon valve, but with the hassle of frozen valves, flooded bathrooms, I wonder if it's really a convenience or not.

Maybe, just disconnecting it from the fresh water supply, routing a water supply to the flush device on the side of the black tank and not having to deal with valves in the wall is a simpler solution than being in the middle of nowhere, at a truck stop, dumping the tank and finding the rest of your vacation is "down the drain" because of a busted valve in the wall.....

[geo]

Hank -

I think if I made a cut access, I would rather do the cut inside the linen closet - less noticeable. And, I do plan on a peek through the electrical socket. .

However, with your advice and JRTJH's thoughts, I believe I do have a plan! JRTJH is correct. The Shark Bite is only rated for water. Testing it would give one comfort, but how long would it last?

B&K has a 1/2" Swing Valve Check Valve that is rated to 150# WOG (water, oil, gas). Perfect! Just install a couple of Flair PEX fittings, and connect the check valve, and I'll no longer have anxieties about water flowing through the transfer switch, or a 50 Amp puddle of water in the basement.

More chores for the Holidays!

Ron

[geo]

JRTJH -

Yes, the connection for the black water flush on the Alpine is similar. There is a separate black tank flush connection in the WaterWorks area. It's all enclosed to keep it warm in the winter. Fresh water hose enters the area from beneath the fiver. Have to open the door to access the black water flush connection. Immediately behind this area is where the pipe ascends into the wall directly over the transfer switch. But in a couple of weeks, that will be changed!

Ron

[hankaye]

Howdy All;

Interesting conversation.

In my 278RKS ('08 version), the black tank flush is located just above the outside shower, my commode is on the opposite side of the trailer and the flush valve sits almost even with the exterior connection yet is 2 to 2.5 feet above the top of the tank.
First time I used the flush system The check valve came apart into several pieces. The interior access was inside the storage compartment to the left of the radio. In another thread I described what I did to repair it. The check-valve in mine was clear and was a Lakeview RV Supply's Model 1000.
That valve also functioned as a vent for tank fumes. Just like the one under the kitchen sink.
The ONLY thing that the hose connection is connected to is the Black Tank Flush valve. It is NOT connected to any other part of the RV's water system. Kind of like the diagram in an eariler post in this thread. It comes in, it goes down to the tank (doesn't go sightseeing anywhere). I use a back flow preventer (check valve), at the spigot when I hook-up the flush system. So, if it needs to vent (other than the roof vent), it can go outside ... at the water connection not inside into the livingroom area.

Ya'll still have me courious as to how or why the flush system is or would be connected into the freshwater system..... Makes absolutly no sense to me?????????????????????????????????? If it was wouldn't you have to turn on/off a valve somewhere in your system to flush the system instead of hooking up another hose and water supply to use it?????????

hankaye

[JRTJH]

Hank, My thoughts as well. I remember on the side of our Holiday Rambler (it had a factory installed black tank flush) about midway up the side wall, the black tank flush connection was inside a water outlet door. The fresh water connection was in a similar door at the lower side of the trailer about the top of the frame level.

I suppose that was HR's way of eliminating a check valve in the wall was to position the water inlet above the tank and all it's parts so nothing could flow uphill (backwards) As I recall, it had the same check valve at the garden hose connection as did the fresh water inlet.

Like you, I can think of no benefit to have a connection between the fresh water and the black tank flush. In the diagram on this thread, it really doesn't appear that there is any common connection. And, yeah, there should be some kind of valve or shut off device to prevent flushing the black tank every time you connect to city water if there is some kind of connection.

I think I like my system more every time I read about the issues other people are facing. I always endorse the KISS method of resolving problems if at all possible.

John

[hankaye]

JRTJH, Howdy;

Originally Posted by JRTJH

Hank, My thoughts as well. I remember on the side of our Holiday Rambler (it had a factory installed black tank flush) about midway up the side wall, the black tank flush connection was inside a water outlet door. The fresh water connection was in a similar door at the lower side of the trailer about the top of the frame level.

I suppose that was HR's way of eliminating a check valve in the wall was to position the water inlet above the tank and all it's parts so nothing could flow uphill (backwards) As I recall, it had the same check valve at the garden hose connection as did the fresh water inlet.

Like you, I can think of no benefit to have a connection between the fresh water and the black tank flush. In the diagram on this thread, it really doesn't appear that there is any common connection. And, yeah, there should be some kind of valve or shut off device to prevent flushing the black tank every time you connect to city water if there is some kind of connection.

I think I like my system more every time I read about the issues other people are facing. I always endorse the KISS method of resolving problems if at all possible.

John

Mine had NO check valve on the inside of the connection like the City water inlet does (except for the cheap A&&ed valve that blew apart), ..... Thought it would before I tore into it wasn't the first time I was wrong .... that's why I got the back flow preventer (about $5.00 at your local Hardware store).

Found my link;

http://www.keystonerv.org/forums/showthread.php?t=2832


hankaye

[DTJ9610]

So that's what it is. Thanks for the research.

[chuck&gail]

THANKS FOR THE PICTURE! I'll put it in my file in the TT.

[geo]

Just an update from recent work.

On my Alpine, the black tank flush plumbing ends at only one injection point. In the diagram and on other add-on systems, it appears those systems have two or more injection points. The one injector on mine is located immediately above the drain valve. I don't know what kind of sprayer or nozzle is inside the tank ... Didn't go that far!

Ron

[CPE]

I think everyone is missing an important function of the valve, also it opens an atmospheric vent (under the top part of the cap) allowing air to enter the line to allow water to drain from the valve to the line. This is a health issue BOCA approval for that exact valve. Commercial back flow valves also have vents. This is part of the yearly certification for these valves in industry and more often in homes, also.
Mine was plumbed backwards and it is in the wall behind the shower valve. (Heartland trailer I had before). I have a license from the County to inspect these valves(attened a 6 week course at local college) of all types as they are becoming more common due to incidents from their non existence or operation. No other type check valve is or should be used for this purpose.
Hope this is not construed as a lecture.

[geo]

CPE -

I cannot speak for everyone, but I do believe that the contributors to this thread do realize what the job of the vacuum breaker/check valve is. My problem, or at least what I think is my problem, is that the rocket scientists at Keystone mounted the Generator Prep Transfer Switch immediately below the pipes and floor access hole to this valve. This means that I have, basically, two opposite syncronized 120VAC 50Amp power lines coming into a non-waterproof box mounted on aluminum frame members grounded out to the frame of the fiver. So, I would guess your imagination right now is running along the same lines as mine - how big of a flash would a water leak make?

Both Hanks, JRTJH and others have had some very good points. Some kind of vacuum breaker or WOG breaker device needs to be on this input water line connected inside a methane/hydrogen sulfide producing tank that could possibly build a pressure head and cause fluid and "stuff" to flow up the input water line. I've put my time in on sour gas wells . . . black water tanks don't "hold a candle" to what those gas wells can do!

I only hope that this thread and discussion will stop someone from taking a WOG breaker device out of the black water tank flush line. And, actually, I tend to doubt the gas stopping capabilities of the vacuum breaker inside the bedroom wall. A good head of pressure, the black water flush sprayer above the "water and goo" line, and a restricted vent line to the roof caused by mud daubbers . . . Eew!

But let me also stress, your input is quite valuable and, personally, I hope you will add to this and any other discussions.

Ron

[hankaye]

CPE, Howdy;

Nope, don't consider it a lecture. Just wonder why, (This applies to my RV ... no one elses), if there is no check vale at the inlet, and the inlet is 2.5 feet above the tank. There is no other system or plumbing connected to it ... just a streight piece of tubing from the hose connection (point A), to the black tank (point B). No way for a finger over the end of the straw trick... why would they put the valve in the system? That's all I'm trying to figure out...

hankaye

[gepaine]

Soon after buying our 2011 Cougar, I had a question about the functioning of the black tank flush system. I called the company that provided the flush system and spoke with the owner (and I think the designer / inventor of the system). During the course of our conversation, he mentioned that about 1 in 100 check valves had failed (cracked I think) in the field. He said if this should happen to mine, just give him a call and he would send me a replacement. He also said I could just remove the check valve and not replace it. He said the check valve was unnecessary because there was no way a vacuum (siphon) could be sustained with a minimum 24-inch rise above the tank connection point. However, his customers (the RV manufacturers) insisted that he include a check valve in the kits he sells to them.

Given the above info and the potential damage from a leaking check valve, I doubt that I would replace mine should it fail. However, I would probably start using a check valve with my flush hose just to be safe.