BACK FLUSH FOR THE BLACK TANK

[prariepoodle]

We arrived at our new location and the first thing we did was dump the black tank, hook up the hose to wash it out and the darn thing is plugged. Tried everything to unplug it but Alas nothing works, we blew it out with the air tank, ran a wire all the way down it don't seem to be anything there. Any one had this problem??? If so what did you do???

[RC and Samantha]

Linda,

We just had that happen in July while we were out in Montana. Turned out to be the check valve under the sink. Dick didn't think that could actually be the cause and when we got the new one to replace it, it didn't sound or look any different than the one he took off. Amazingly though replacing it was all it took and the black tank flush is working again.

I think we'll order another one to keep in the unit just in case. The whole repair didn't take 5 minutes and required no tools, just his strong hands.

Patty

[prariepoodle]

Thank you,Thank you Patty, Walt just took ours off and sure enough it is bad. We did not even know there was a pressure valve under the sink. Walt is off to the RV Store to see if they have one. Again The MOC comes through, I just love this forum.

[patodonn]

That little valve is a anti-siphon valve, designed to keep "black" tank flush water from getting back into RV park's (and city supply) supply line by siphon action or any other way. Mine failed in the same manner as yours while "on the road", and I ended up removing the valve and just hooking up the two lines using a connector found at almost any RV store. I do use an "anti-back flow" connector on the end of the fill hose, which serves the same purpose as the removed valve. Cost was about $2 at a hardware store garden department. I may end up getting a replacement "anti-siphon" valve part one of these days...but works fine for now.

[richfaa]

The failure of the black tank anti siphon valve has been added to my "how come" list for our factory visit in Oct.That list is getting to be very long.

[RKassl]

Is this valve in the same place on all Montana models? I have a 2955 and would like to know where it is. Is it on the fresh water system and what does it look like?

Thanks!

[Illini Trekker]

Bob it's also under the bathroom sink. If mine goes bad I'll do as PJ has and do it a better way.

[prariepoodle]

Well this is a bummer Walt had to buy the whole kit just to get the check valve at the cost of $21.34 He told the salesman that he was not building a RV just changing the valve.LOL Don't know when we will ever get to use the rest of it.

[prariepoodle]

Well gang that did not work either, hooked up hose nothing went into the tank lots of pressure on the hose, drowned walt when he took the hose off. Back to the drawing board. It worked when we started this trip. What to do, what to do?????????? richfaa, I would be interested in knowing what you find out at the factory.

Update: Removed new pressure valve completely,installed elbow to make it direct and still no water will go to tank, so it must be plugged somewhere. Anyone know who makes this so called No Fuss Flush? Maybe they could shed some light on what is going on. Sure hope none of you have this problem.

[CountryGuy]

Linda and Walt,

I don't know anything about the plumbing, except that sometimes I hear people talking about the vents to the roof being plugged with bugs and stuff. Just a thought!

Again, thinking out loud, I might try filling the toilet and flushing, till you think you have say, 1/3 full, then drain, do a few times, then maybe 1/2 full and drain. Adding a lot of water to the toilet, in another way.

Also would check around to be sure you don't have water coming out of a leak in any of the plumbing, check the basement etc for water that should not be there.

Probably none of these ideas are any good, but they is all I got !! Al is not here, so I cannot ask him.

Good luck!

[Illini Trekker]

I'd try rodding the line out at the check valve location. There are surely less bends to make with the wire there. If the black tank is empty, you could drop some of the underbelly to get to the connection at the tank. There should be a screw on connection there. Best of luck!

[prariepoodle]

I sure do thank all of you for your input and we will keep trying but it will have to wait till we return from Florida as we are leaving early in the morning and will be gone a few weeks. I have to say I will worry about this until we find out what is wrong and why it happened.

[Just148]

Just a though, check all the lines to see if there is something pinching one.....

[sreigle]

Linda, a shot in the dark... If I recall, where you connect the hose is a screen to keep debris out. Remove that screen and see if there's a little white button behind it. If there is, that's also a one-way check valve. It's possible that valve broke or the o-ring slipped out and is blocking water from getting in. I had this happen on the city water inlet once.

[DHenry]

How do you get that check valve out of there?

[tundra rose]

We just had this problem with our 2955. The dealer had to remove the belly pan under the black water holding tank and disconnect the water line from the nozzle that is attached to the tank. After $133 in labor, he found that the orifaces that are on the inside of the tank were clogged with toilet paper. He was able to clear them with a pick to the point that water now flows thru the system.

Several local RV shops have provided the following advice for clearing such clogged nozzles:
- Empty the tank, then fill it completely with water and a good 'digester', and let it sit for several days before flushing.
- If that does not work, attempt to clear the holes from the outside of the tank.
- If all else fails - remove the nozzle from the tank, clean it and then reinstall it with a new application of silicone sealant.

I have also found that you can test the backflow preventer valve (located in the bathroom sink cabinet) by removing it and connecting it to the shower hose. If water will flow thru the valve, it is easy to determine if the valve the problem.

Steve, to my knowledge the hose bib connection does not have a check valve.

[sreigle]

Doug, if it has one you'd probably have to replace the entire bib if you can't work the o-ring back into place. The second time this happened I had to replace the entire city water inlet. The first time I was able to get the o-ring back in place. Both were on a non-Montana.

Ted, you may well be right, especially since there is a check valve inside the rig. I've not heard before of the orificies being clogged but that makes sense. I guess I need to do some research as I'd like to see how this thing works, anyhow.

[Dave e Victoria]

I'm still back there trying to figure out how a backflow preventer in the kitchen or sink could effect the blacktank flush. I thought the black tank flush was a direct connection to the outside hose bib with no other connections. Am I that screwed up? Please enlighten me?

[tundra rose]

The water line on ours goes from the outside connection, into and across the basement, up into the bathroom sink cabinet to the vacuum breaker, and then back into the basement to the holding tank.

I have not yet found a website for Lakeview RV Supply; however, did find the following brief description of how the system works in a Google search.

"A system designed to flush recreational vehicle wasteholding tanks. The system shall be equipped with a listed atmospheric vacuum breaker located a minimum of six inches (6") above the flood level rim of the highest fixture connected to the tank. A listed check valve shall be installed horizontally immediately on the discharge side of the vacuum breaker."

Steve, in one of your conversations with Keystone, you might ask them why the vacuum breaker is located in the bathroom sink cabinet . I assume that it is the best place inside the trailer that is 6" above the toilet rim.

Our vacuum breaker (Model 1000) has an integral check valve in it. Should it ever fail, I intend to replace it in kind. If someone were to remove it, they need to at least install a new check valve.

[Dave e Victoria]

OK, Now I understand. It is just a convenient place to hide the little device. It is not hooked ino bathroom or kitchen plumbing. (Oh, it is so good to be enlightened.) Now, I am going to go look for it in our coach -- just for fuure reference.