Ok all you *Plumbing* wizards, looking for advice

[arcaguy]

Yes your assumption about the "flushing hose" is correct the one connected to city water to flush your black tank. As to your second question the water city/RV park water system can malfunction by losing pressure for whatever reason, loss of power, pump going bad etc. In that case if anyone opens a valve that is lower in elevation that your tank flush "city" water connection it will start siphoning from anywhere there is a place for air to enter the system, in this case your black tank. As far as any check valve goes I don't know for sure if there is one in that piece of brass or not, but even if there is a check valve, just like anti-siphon valves, they are prone to failure and sometimes need a fair amount of back pressure to close. With all of that said I have not inspected the system in person so I really don't know what is going on but I'm trying to give you thinks to think about so maybe you can understand what is going on.

[alank]

Originally Posted by arcaguy

Personally I'd just take the anti-siphon valve out and be done with it. I know it's not code and it de-idiot proofs your RV but those things are more trouble than they are worth. The only time they would come into play is if you left your flushing hose connected to the water supply and the water supply malfunctioned creating suction from your black tank. There's three things that have to happen simultaneously here for the to be a problem. First you have to leave the black tank flush connected to the water supply. The second is the water supply has to cease working and three there has to be water leaving the system to create suction to siphon the black tank. I'd bet on Elon Musk setting up shop on Mars before I'd be all three of those things happening at the same time. The chances of that siphon break leaking at some point are nearly 100% with the resulting damage to your coach. Just my thoughts. The throwing of bricks can commence now.

Actually, I like your thinking because I've already removed my anti-siphon valve. I still have the backflow valve that was part of the anti-siphon valve, and I have another backflow valve in the water bay where the hose hooks up. My valve was plastic and I cut the top off, removed the actual valve from the valve body, and machined a press fit brass plug to put in the hole with a clip on top just to be sure it doesn't come out. No worries any more about a shower under the 1/2 bath sink.

[FIRE UP]

Well gang,
Here's the latest news from the *anti-siphon front*. Well, I took some advice and, I tested the system before I re-installed the wall paneling. My air pressure tests indicated that, I had zero problems with flow. The hoses, the valves, and all, flowed air just fine. So, the true test was to hook up a water hose to the flush port in the wet bay and, turn it ON.

I did that and, jumped in the coach to check out my work. CRAP! It's leaking!!!!!!!!! Yes, the system is flowing water and that means the tank is being flushed out. But, it also means I'd have water wetting INSIDE that wall, not good. Sooooo, out came that valve assembly and back to the work bench. I sat there and looked at it for about a minute. That's all it took for me to decide, shi...can it!!!!!

I then jumped on my trusty motorcycle and headed down to the local hardware store. There, I picked up a 1/2" PVC thread x thread 90. Zoomed (well, with the present snow bird traffic, CRAWLED) back home and put the 90 on and put the assembly back on the hoses. I then turned the water back on and went into check the work. YAHOOOOOO, NO LEAKS!

I did however, leave the plastic body check valve in place. But, when I checked for water flowing, I could hear the high volume of water hitting the insides of the tank. So, the flow is definitely not restricted by that check valve. So, I secured that assembly to a wall stud/brace and, reinstalled the wall paneling. Just have to re-hang a mirror and this project is DONE. I want to thank all who've contributed to this thread. Lots of great info here.
Scott

[fcbbob15]

Smart move getting that vacum breaker out of the wall. Just install an external one and be done with it.

[FIRE UP]

Originally Posted by fcbbob15

Smart move getting that vacum breaker out of the wall. Just install an external one and be done with it.

Well,
That's waaaaaaaaay easier said than done. You see, the only plumbing lines for that flush system, are what you see INSIDE that wall. Once that wall is put back together, there is no real way to install an "external" one. So, for now, it's gonna be left the way it is, without one (anti-siphon valve) in place. If, at a later date, I find any problems with the system the way it is, I will deal with it then.
Scott

[Piros1]

Originally Posted by FIRE UP

Well,
That's waaaaaaaaay easier said than done. You see, the only plumbing lines for that flush system, are what you see INSIDE that wall. Once that wall is put back together, there is no real way to install an "external" one. So, for now, it's gonna be left the way it is, without one (anti-siphon valve) in place. If, at a later date, I find any problems with the system the way it is, I will deal with it then.
Scott

Scott you know they make a vacuum breaker/anti siphon valve that will screw into where your flush hose connects. Available at most hardware stores. This will keep any bacteria from getting into the hose and water system you are using to flush your tanks. I believe this was mentioned earlier in one of the post. They suggested that you go as you did and install the garden hose back flow preventer as I just suggested. Your call but those who follow behind you would appreciate it.

[Piros1]

Here is a link to what I’m referring to.
https://www.amazon.com/Litorange-Con...dDbGljaz10cnVl

[lonfu]

Originally Posted by FIRE UP

Well gang,
Here's the latest news from the *anti-siphon front*. Well, I took some advice and, I tested the system before I re-installed the wall paneling. My air pressure tests indicated that, I had zero problems with flow. The hoses, the valves, and all, flowed air just fine. So, the true test was to hook up a water hose to the flush port in the wet bay and, turn it ON.

I did that and, jumped in the coach to check out my work. CRAP! It's leaking!!!!!!!!! Yes, the system is flowing water and that means the tank is being flushed out. But, it also means I'd have water wetting INSIDE that wall, not good. Sooooo, out came that valve assembly and back to the work bench. I sat there and looked at it for about a minute. That's all it took for me to decide, shi...can it!!!!!

I then jumped on my trusty motorcycle and headed down to the local hardware store. There, I picked up a 1/2" PVC thread x thread 90. Zoomed (well, with the present snow bird traffic, CRAWLED) back home and put the 90 on and put the assembly back on the hoses. I then turned the water back on and went into check the work. YAHOOOOOO, NO LEAKS!

I did however, leave the plastic body check valve in place. But, when I checked for water flowing, I could hear the high volume of water hitting the insides of the tank. So, the flow is definitely not restricted by that check valve. So, I secured that assembly to a wall stud/brace and, reinstalled the wall paneling. Just have to re-hang a mirror and this project is DONE. I want to thank all who've contributed to this thread. Lots of great info here.
Scott

a smart move... best way to handle it and never have to deal with it again, as long as you glued it...

[Old-Biscuit]

That is what I suggested in post #26

[FIRE UP]

Originally Posted by Piros1

Scott you know they make a vacuum breaker/anti siphon valve that will screw into where your flush hose connects. Available at most hardware stores. This will keep any bacteria from getting into the hose and water system you are using to flush your tanks. I believe this was mentioned earlier in one of the post. They suggested that you go as you did and install the garden hose back flow preventer as I just suggested. Your call but those who follow behind you would appreciate it.

Well,
Not being a plumbing wizard, what I might ask in this situation is, removing the vacuum breaker simply stops a siphoning effect that *could* siphon black water backwards, in the direction of the connection point in the wet bay, correct? Well, then what is the one-way check valve (plastic one) in that line for? To me, from where you hook your garden hose up to, right there in the wet bay, to that check valve, there should never, ever be any black water on this side of that check valve, correct? I mean, isn't that what's the check valves duty is?
Scott

[stancanyon]

I will never have a vacuum breaker in a "dry" area anywhere! Sometimes the Code will screw you up, and it did me in this situation, except it was in my HOUSE, and when the vacuum breaker stuck open (it is a MOVING PART!), my house was flooded, three floors, and a nightmare of soaked floors and ceilings,carpets, insulation, blah, blah! $85,000 of damage because of a 99.9% useless piece of equipment, and this was a $180 Watts full size 3/4" lovely pro piece of foolishness....
Do what these gentlemen suggest and get rid of it, or move it to the wet bay if you think you really need that much idiot-proofing...

[AlexP]

Fire Up,
I have the same unit 2004 36G Meridian. I noticed that there was water on top of my black tank. It was coming from this fitting.


On mine both hoses going into this fitting were carefully screwed to the supports in the wall so mine was upright. I ordered a new one from supplyhouse.com description 1/2" NPT BFP V-101 Anti-Siphon Vacuum Breaker, Brass (Lead Free). Stock number 17383-0000LF. $17.


When I got the old one out, it appeared that when it was put together a little too much teflon tape got into the joint and that worked its way into the mechanism. So I probably didn't need to replace it.


But no leaks now.
Alex

[NomadRider]

I've been designing plumbing systems for commercial/industrial buildings for over 40 years so I know a bit about these things.

That brass thing that y'all have been calling everything from a backflow preventer to siphon break is technically called an anti-siphon vacuum breaker. A relatively simple device, its sole purpose is to protect the potable water supply.

Although I'm not at all familiar with the RVIA codes, I'm certain that when it comes to plumbing systems they're based on the standard plumbing codes which is what I'm basing my commentary on.

To be installed correctly, the vacuum breaker must be oriented to have a bottom inlet and side outlet, with the little disk at the top. It must be located at an elevation higher than the flood level rim of the lowest fixture connected to the black tank.
Some of these devices are serviceable, some aren't. They have different styles - some with a brass disc some with a rubber diaphragm.

They operate on a simple principle - at rest, the brass disc will be seated against the inlet allowing the free flow of air downstream of the device from its outlet to the termination of the piping connected to it. In a typical plumbing system these devices are used at what are considered low hazard applications - for example at a sink that has a hose connected to it that might be submerged.

So why is it required?
First, these devices are to protect the municipal (campground/whatever) supply - NOT you. You can do whatever you want in your house/coach.
Second, there are documented cases of people dying from contaminated water supplies - it's nothing to fool around with. Don't second guess the need for this device!

Let's say you remove this device. You've hooked up your hose to the black tank flush and turned the water on to begin the flushing procedure. While that's going on you get distracted chatting with the camper one site over - talking about the sirens you heard a little while ago. You're only gone for a few minutes and you're back. While you were gone the fire truck pumper truck that belonged to that siren you heard hooked up and began pumping. Immediately, it causes a system-wide drop in water pressure - so significant that water begins flowing backwards. That pumper is super powerful and it will get its water. Since you removed the vacuum breaker, there is nothing to stop that pumper truck from drawing water out of your black tank and guess what? You've just contaminated the municipal water supply. If your neighbor drinks that contaminated water, he'll certainly get sick. Hopefully he won't die.

That's just one possible scenario - believe me these things can and do happen. Upstream pressure drops can be caused by all sorts of things - pump malfunctions, ruptured mains, industrial incidents, whatever.

As for the check valve that is located downstream of the vacuum breaker, its sole purpose is to "keep the stink out". It is not commonly used in conventional plumbing systems. It will be a spring loaded valve that closes against the direction of flow to prevent black tank odors from permeating the coach. Importantly, it is not considered a positive means of preventing the reverse flow of water!

Commonly, RV vacuum breakers are located under the lavatory or some other accessible place so that they can be serviced. Inside of a wall is a lousy place for it.

Someone recommended using a vacuum breaker of the type that is commonly used on a hose bibb. Those devices are much lower quality - typically only a rubber diaphragm and they will not be as reliable as the brass (or even plastic) vacuum breakers. There are at least two problems with them - one, when connected at the black tank flush, they are not above the flood level of the fixtures served meaning that all of the piping can potentially be contaminated and two, the biggest problem with them, is that they are not permanent. Someone that doesn't know that the permanent vacuum breaker has been removed might not know that the device is required and not use it - "after all, none of my other RVs required that thing!"

To protect the water supply - the devices must be a reliable and fool-proof as possible. Please, never remove the vacuum breaker.

[samsonsdriver]

On the plus side, it doesnt look there is any water damage there!