Black tank flush system

[JRTJH]

Originally Posted by rbrdriver

If you put in a 90 degree fitting in place of the backflow fitting does it really matter that you don't have said fitting anywhere in your hookup? I'm sure there is a code somewhere that says you should, but who's to know? Just saying.......

The problem is not "who's to know?" Rather it's, "If things go south and you have a siphon of black tank contents, could it/will it contaminate the entire campground fresh water system?".... That, should it happen, is, in a limited way, the same as the Flint public water debacle.....

You really don't want to be identified as the "code violator who contaminated the KOA"....

[rbrdriver]

Point taken. I assume there is an anti-siphon valve I can insert in my water connection to the flush out system should I have to remove the one in the coach for some reason.

[JRTJH]

There are many styles. Here's one type that will connect between the black tank flush fitting on the side of your trailer and the dedicated hose you use to flush your black tank: https://www.amazon.com/Mueller-108-9...%2C205&sr=8-17

[travelin texans]

Originally Posted by JRTJH

There are many styles. Here's one type that will connect between the black tank flush fitting on the side of your trailer and the dedicated hose you use to flush your black tank: https://www.amazon.com/Mueller-108-9...%2C205&sr=8-17

This is the type I mentioned in post #13 that tend to leak once hose pressure is released til it closes.
I'm no rocket scientist but on my 5th wheels the anti siphon was 4'+ straight up above the black tank then dropped that far straight to the outside connection, I've siphoned enough gas to know that's a helluva vacuum to get that siphon started.
I do understand the reasoning for it, but the odds of it happening in the RVs I've owned would be slim to none.

[JRTJH]

Originally Posted by travelin texans

This is the type I mentioned in post #13 that tend to leak once hose pressure is released til it closes.
I'm no rocket scientist but on my 5th wheels the anti siphon was 4'+ straight up above the black tank then dropped that far straight to the outside connection, I've siphoned enough gas to know that's a helluva vacuum to get that siphon started.
I do understand the reasoning for it, but the odds of it happening in the RVs I've owned would be slim to none.

That's why I said, "If things go south....." Sure, I completely agree with you, chances of it happening are extremely remote" but it's a possibility (however remote) just like "they said" it'll never reach 100F in northern Michigan, but, last year, 3 days and so far this year 2... So, "never happens" does, at times, happen.....

Think about the guy that pressurized his black tank and it was coming up the toilet, pushing past the ball valve into the bowl... If he'd have quickly turned off his water, what kind of pressure "could have been" in that hose without a backflow preventer ??? Like I said, "a perfect storm situation" but not an "impossible situation".....

I'm seeing more and more campgrounds with "backflow preventers" on their fresh water faucets. I'd suppose they aren't there because they wanted to spend money on something that could be easily stolen... I'd suspect they're there because they don't want someone with a "modified black tank flush system" connecting to their campground fresh water system and "taking the risk that their missing anti-siphon valve under the sink won't make a difference"....

Not sure if it's one in a thousand, one in a hundred thousand or one in a million.... Really, if it happens to me, it's "one too many"....

[Javi]

Originally Posted by rbrdriver

If you put in a 90 degree fitting in place of the backflow fitting does it really matter that you don't have said fitting anywhere in your hookup? I'm sure there is a code somewhere that says you should, but who's to know? Just saying.......

I'm a Texas redneck wasn't worried about the code.... I just figured that a $5 vacuum breaker wasn't going to break the bank and might prevent a mess that I'd feel compelled to clean up... 😁

[Papa of 7]

Yes, mine is installed backwards, I am not going to use it. My question is the flush attachment with a 45 or 90 degree wash that attaches to the blackwater pipe, is there a better one and should it be with a gate valve or without. Tell me your thoughts!

[JRTJH]

Originally Posted by Papa of 7

Yes, mine is installed backwards, I am not going to use it. My question is the flush attachment with a 45 or 90 degree wash that attaches to the blackwater pipe, is there a better one and should it be with a gate valve or without. Tell me your thoughts!

I think you're asking about the "terminal connection type flush device" ???

IF so, depending on the number of 45 or 90 degree fittings that connect that fitting with the black tank outlet, any "flush device" that claims "high pressure water from the hose fitting into the black tank" will fail to produce that high pressure spray into the black tank. Each of those bends/elbows in the 3" outlet pipe will reduce the "spray" to a "influx of water" into the black tank. Essentially, the bends in the outlet pipe reduce the "flush device" to a "fill and dump device".... They are good for rinsing the black tank (by diluting the black tank contents) but they don't provide for any "water spray that hits the black tank sidewalls".... All of those "bends in the outlet" from the place where you add on that flush device back to the black tank entry opening, make for "no spray reaching the black tank interior walls"...

Now, if you've got a "straight shot of 3" PVC pipe from the outlet fitting to the tank outlet" and it's not "too long of a pipe" you might get some "water spray directly on the wall opposite the tank opening"... The other three walls, there's no way to "bend the spray to clean the tank interior".....

[Reider98]

Guarantee they installed it backwards. They did it to my 2020 Cougar. Very common problem. You would think the factory would have addressed this problem. Good luck.

[analogkid]

Had the exact same issue on my 2020 Sprinter. Called the dealer and before I could finish describing the problem the lady helping me laughed and said “sounds like another with the check valve installed backwards”. I took it in and big shock - it’s exactly what was wrong. Sounds like this is VERY common.

[Papa of 7]

Looks like I will modify it was something better as someone mentioned previously.

[jimborokz]

Originally Posted by travelin texans

This is the type I mentioned in post #13 that tend to leak once hose pressure is released til it closes.
I'm no rocket scientist but on my 5th wheels the anti siphon was 4'+ straight up above the black tank then dropped that far straight to the outside connection, I've siphoned enough gas to know that's a helluva vacuum to get that siphon started.
I do understand the reasoning for it, but the odds of it happening in the RVs I've owned would be slim to none.

I use this device on my black tank flush line, but I put it at the spigot end of the hose. That way I don't get sprayed on when I shut it off. And that 10' length of hose is used only for the tank flush and never anything else.

[Javi]

Originally Posted by travelin texans

This is the type I mentioned in post #13 that tend to leak once hose pressure is released til it closes.
I'm no rocket scientist but on my 5th wheels the anti siphon was 4'+ straight up above the black tank then dropped that far straight to the outside connection, I've siphoned enough gas to know that's a helluva vacuum to get that siphon started.
I do understand the reasoning for it, but the odds of it happening in the RVs I've owned would be slim to none.

They don't TEND to leak, they are designed to leak...

That's how they break the suction...

Many campgrounds I've visited have these installed at the spigot with the set screw broken so it can't be removed.

[flybouy]

Originally Posted by travelin texans

This is the type I mentioned in post #13 that tend to leak once hose pressure is released til it closes.
I'm no rocket scientist but on my 5th wheels the anti siphon was 4'+ straight up above the black tank then dropped that far straight to the outside connection, I've siphoned enough gas to know that's a helluva vacuum to get that siphon started.
I do understand the reasoning for it, but the odds of it happening in the RVs I've owned would be slim to none.

Don't want to argue but here's the difference between "sucking on the end of a hose" and having the hose filled to begin with. At sea level a siphon will work up to about 30' depending on barometric pressure. So if the hose is flowing water to the tank and the water line breaks somewhere lower then the tank then it can easily suck the tank contents back into the hose and pipe.

Think of it this way, let's say a 2" main breas 100 feet away. In effect, that area of pipe from that hose/tank (if it's the only place for air to enter) would effectively be the same as a piston of that area drawing the water back like a syringe in a vein.

I have a small pond in the back yard that I drain and clean every spring. I used an old pond pump to drain it until it died. After it died I use a 10' hose to drain it. The "deep end" is several feet deep. I just place the entire hose in the water, cover the end I'm going to take out with my thumb, then remove my thumb when the I get the end of the hose lower than the bottom of the pond. Atmospheric pressure does the rest.

[reelfun]

Water lines Crossed under Sink check and follow all lines.

[Whitewolf]

I probably use just about the same thing as Danny of the Travelin Texans use. Just the other day I noticed water dripping into the basement below the bathroom sink from the valve. That's our second valve and it'll be gone soon.