Black Tank Flush Line

[sola123]

Our black tank flush has never really worked so today we traced the lines and found that it enters the basement and is routed thru the floor and under the bathroom sink, is connected to a black object I assume is a back flush valve and then it runs back down in the basement to the tank...does everyone else's do the same?...and why is it located there and not just in the basement at an elevated level above the tanks..under the sink it is about 4 feet or more above the tank..I think the valve is apparently put on backwards as you can not blow thru the line but can draw air out...I want to move it all to the basement...would appreciate anyones thought on this....

[Trailer Trash 2]

Stan the anti syfon valve under the sink could be bad get a threded elbow on each end ( a splice ) then see if water gets into the tank if it works its the anti syfon Valve . If that dont wor call me at I sent the phone number on your PM I'll tell you what I had to do to fix mine.


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[bncinwv]

I think it is the check valve to prevent backflow. They do fail regularly. Was it subjected to freezing temperatures and not winterized (blown out or putting pink stuff through it)?? Just a hunch.
Bingo

[sola123]

Thanks for the help...we got it fixed today....the ball was stuck...since it has the ball and flap we removed the ball and it works just fine...can't imagine it siphoning back all that far....so problem solved...thanks for your help...we do blow our unit out to winterize it and have never had a problem yet....

[bncinwv]

Stan,
If I read correctly, you removed the ball or did you replace it. If the valve is higher than the connection in the convenience center, then the siphon will be created by the length of the line to that point and I would guess that would provide a pretty good suction (6 or 7 feet of hose?). If you did remove the ball completely, I think I would stand clear at least the first time disconnecting the hose from the black tank sprayer connection. There may be some residue at the bottom of the tank that possibly could be vacuumed out and result in an unwanted situation when the spray water clears. I would be curious as to what happens when you do try it (out of curiosity of course, no other reason).
Bingo

[Trailer Trash 2]

regardless you got it fixed, if you ever have a problem with the spray nozel getting pluged use a bottle of rid ex and fill up the tank to the top and let it soak for a couple of days that rid ex will eat anything in there and make it squeekey clean along with unpluging your fast flush system nozel.

[Ozz]

That's a anti-siphon device.
This prevents sucking Black water...yuck! into your fresh water system. The reason it is up so high is so it breaks any siphon action. I would not adapt it in any way, if it is bad, I would replace it. They put it up high for a reason, if it were me, I would leave it there.
It looks like Don has some good info for you.

[bncinwv]

Ozz,
There is not a physical connection between the black tank spray and the fresh water system since the tank sprayer has a dedicated hose connector in the convenience center. There is however, a strong possibility of some unwanted back-splash if you are standing at the convenience center when you disconnect the hose from the nozzle (only if the anti-siphon valve has been eliminated from the system). That is what I am afraid that Stan might of done. I agree with your statement about Don's suggestion, that is some good advice which I will definitely remember.
Bingo

[Ozz]

But... does the hose connection not connect to the fresh water hose bib? That could back-feed to the park water supply, then to a RV.
Many have a Y-connector that feeds both the water supply and the flush, so they don't have to unhook.

[bncinwv]

Good point, I have never and would never hook both up at the same time to the bib, but I do remember some previous postings that describe the y-connector you mentioned as well as the dual hookup. To each his/her own I guess???
Bingo

[Ozz]

I do, but I have an additional vacuum breaker at the Y-connector, I figure two in the system should protect my water supply.
When you think about it, you should never get Black water unless the tank is so full it is above the tank cleaner nozzle. Under certain conditions I guess people have it happen.
With the hose connected solely from the park water supply to the tank cleaner input, it can suck back contaminated water into the park water supply with a defective vacuum breaker.
That is why most parks have a vacuum breaker on their supply hose bibs. It is code, but many do not follow code on anything...