Black tank flush

[glb1950]

Question. On our 21 3762BP there is a hose inlet labeled "black tank flush". When I hook up the hose to it and turn it on, the hose is really hard like it's not going anywhere. Is there something else I have to turn on, switch to throw, valve to open? Thanks.

[twindman]

If you listen closely you can hear a sprayer under the trailer if it is working. If you don't hear it, then it must be plugged up somewhere. The old units used to have backflow preventer - in many cases under the bathroom sink. In some it was actually inside the wall near the bathroom. If here I think they have a cover plate over the hole to get at it, but maybe the owner has to cut it when there is a problem.
First place is look under the sink for 2 hoses (pex?) coming out of the floor with a gizmo connecting them. I know things change often, but this is what my 2013 had in it until it leaked and I just removed it.

[jcurtis934]

Assuming keystone hasn't re-engineered the simple tank flush...the plumbing route is from the center to a high point in the bath area and then down to the belly of the beast and to the front center of the black tank. The sprayer was a simple plastic fitting with three holes in its face. So there is only two places for blockage. The plastic fitting at the high point in the bath area and the sprayer. John

[riflegunbuilder]

Mine got plugged. Getting the plastic under belly down and back up took longer than fixing it.

[glb1950]

Thanks everyone. Right now with the weather goin bad, might wait till spring or the sun, which ever comes first and will investigate further since apparently there are no more things I have to do to make it work. If it's a plug I guess it can wait a little bit. Just sorta wanted to flush it out a wee bit. Thanks again.

[DutchmenSport]

The anti-syphon valve could have been installed backwards? Before buying a new one, just "try" reversing it and see what happens.

[glb1950]

Originally Posted by DutchmenSport

The anti-syphon valve could have been installed backwards? Before buying a new one, just "try" reversing it and see what happens.

And can I assume the anti-siphon valve is located behind the panel with the hose fitting?

[RMcNeal]

The anti siphon valve is usually located under the bathroom sink. It should have white pex into and out of the valve. I has to be installed at a level higher than the toilet so they make a loop coming up under the sink, then back down to the black tank sprayer. Most everyone has just removed this and put a backflow preventer on the hose connection in the convenience center.

[ChuckS]

On some Montana's the anti siphon valve is located behind the sliding bathroom door.. On others under bathroom sink..

Regardless.... it IS there unless previously removed... and it is a piece of plastic junk that has a track record for cracking and leaking water all over the inside of the bathroom

Yours is either installed backwards or the diaphragm valve is stuck

Locate it, remove it and toss it in the trash and union those two lines together..

If you just gotta have an anti siphon device in line then use a standard garden hose anti siphon valve and screw it onto your hose end and then to the black tank flush port.

[glb1950]

Ok, was under the bathroom sink with flashlight yesterday and was wondering if that thing on the white pex was indeed the anti-siphon valve. Now I know. Thanks for all the posts on this beast, I'll straight line it and get one on the end of the supply hose.

[RMcNeal]

Depending on how yours is plumbed, you may be able to cut the loop out entirely in the basement. I did that on mine and removed about 6 feet of pex.

[twindman]

FYI. Mine was apparently plugged up once upon a time. I turned off the water and took the valve apart. It was nothing more than a cylinder with a small plastic ball in it. There were stops on the output end so it wouldn't completely close the flow, but on the input end, it had a nice fit with the ball to stop water going that direction. I just took the ball out!!! Worked fine after that.

[Wisconsin Retiree]

Cheap Amazon replacement

https://www.amazon.com/dp/B085CNLP9R...VR7579WR47062V

[dennis hogan]

You can also get the clear adapter with a back flush ( hose connection ) on it until you can investigate the problem. With just the black tank doing it's normal draining when dumping won't get all the STUFF out of your tank. About $20.00

[FATBOY05]

On mine there is one in the inlet where you hook your hose , it has a piece that I depress with a washer with the screen that protrudes outwards . I can take a picture if you want after the Sun comes up .

[CADman_KS]

Originally Posted by DutchmenSport

The anti-syphon valve could have been installed backwards? Before buying a new one, just "try" reversing it and see what happens.

This is what happened when ours was built.

The way that they do this is really kind of silly. Both PEX pipes are white, and they both come up thru the floor in the same hole. So, it's a 50/50 shot that when the anti-syphon valve is installed it will be installed correctly.

Why not take an extra 30 seconds and wrap the supply end with tape, or mark it with a sharpie, but do something to identify it, so that the installer at least has a chance of getting it correct...

[ShaneGreen]

Mine had two issues when I bought it.
1) there was a little trash filter where you connect the hose. One of those washers with the cone shaped screen. It did it's job and clogged after just a few hook ups.


2) I thought I'd be slick and use one of those collapsible "pocket hoses" that they advertise on late-night tv. It would hardly take up any room when I wasn't using it...right? Well the cheep ones are made with a really tiny diameter tubing. Between the trash filter, backflow valve, 25 feet of hose, 20 feet of pex and the sprayer in the tank there was so much resistance that all I got was a dribble. Changed to a regular sized hose and everything worked. Well, until the backflow under the sink gave out and flooded the basement.

[CADman_KS]

Originally Posted by ShaneGreen

...


2) I thought I'd be slick and use one of those collapsible "pocket hoses" that they advertise on late-night tv. It would hardly take up any room when I wasn't using it...right? Well the cheep ones are made with a really tiny diameter tubing. ...

LOL. I didn't buy a collapsible type, but I bought the flexible type, and I thought that I bought a good quality one. The kind that never kinks, yada-yada-yada. I ABSOLUTELY HATE THAT THING!!! The only time that I use it is when I need a 100' hose. Otherwise, it takes me 10 minutes to get all of the kinks out of it, and working properly...

UGH... Lessons learned, I guess...