Black Water Flush Issue - Montana Owners Club

barmar · 05-02-2015, 08:41 AM

Seems that the black water flush system on my Monty is not working efficiently and not at the same flow rate I used to get when flushing. When flushing, and the water pressure is good, there are some weird and variable noises/sounds coming from the area behind the shower where I expect there's some sort of valve but not certain. Could this valve or some other valve be the problem and if so, how do you access these valves?

Any ideas or help would be appreciated. Did a search but didn't find anything under maintenance.

**DQDick** · 05-02-2015, 09:55 AM

You may have one of the models that have their backflow preventers behind the shower. Usually there is a way to access it on the other side of the wall, although some have had to enlarge the hole. Many of us have removed it altogether and now use an external one. Here's just one thread: http://www.montanaowners.com/forums/...erms=back,flow

BB_TX · 05-02-2015, 11:34 AM

There have been many posts about those valves leaking. But don't remember a post about one making noises.

Mine was between the shower wall and the back wall of the entry closet/cabinet, the wall into which the pocket door goes. I say was because it is not there any more. There was a plastic panel covering an opening in the cabinet wall but not exactly where the valve was located. I could reach my hand in and feel the valve, so I cut a new opening at that location.

The upper panel was already there. The new opening shows where the valve was located before I eliminated it. Note the flush line is winterized.

Using the cutout piece and a little trim work and looks like it was made that way.

Here is what the valve looked like. I use an anti backflow valve at the hose connection now.

jcurtis934 · 05-02-2015, 03:35 PM

Mine, before I removed it in favor of one outside the rv, was black plastic and it made a lot of noise when I turned on the system. It also didn't do that great of a job. John

barmar · 05-03-2015, 06:16 AM

Thanks for the replies folks!! In my rig there is no plastic/access plate in the cupboards that back on the pocket door/shower area and I can't see any plumbing/valves when I look in the pocket door space between the cupboard wall and the shower wall--it's a small area and difficult to get a good view. So, if the problem valve is back there how do I determine where to cut a hole in the cupboard to gain access to the plumbing/valve? Thanks, B

rohrmann · 05-03-2015, 07:52 AM

I have not had a problem with my valve yet, but was able to see the valve by closing the pocket door, pushing the edge toward the shower and using a flashlight, could see the valve.

BB_TX · 05-03-2015, 08:09 AM

First, did you look under the bathroom sink to make sure the valve is not under there? Many have found theirs there.

For locating the valve I see only two options. Remove the pocket door so you can see inside the wall. Not a particularly easy job from what I understand. Or cut an exploratory opening in the cupboard wall. Get lucky and it may be over the valve. If not hope you can see or reach in and feel the valve. My shower valve is (nearly) right behind the original plastic panel. So you can see where the flush valve on mine is in respect to the shower valve. The two extra water lines in the picture go to the shower. Don't know if that means anything or not.

Using a cheap mitre box it is easy to make a picture frame around the piece(s) you cut out and make neat looking covers for the openings. The opening needs to large enough to work thru.

barmar · 05-03-2015, 11:23 AM

Got access to the Back Flow Check Valve and plan either to replace it or bypass it as BB_TX and many have done but first, the current valve has manufacturer info on it including temp and pressure ratings like 125 deg F and 25 PSI---does this valve actually reduce line pressure to 25 PSI to flush the tanks or not? If so, then bypassing could be a problem. Thanks to all for the info?/help.

rohrmann · 05-03-2015, 04:13 PM

Maybe that's why some of them are failing, they are only able to stay together up to 25 psi. The temp and pressure ratings are the working ratings, what the valve is able to work at. It is not a pressure regulator. It would be nice if they were rated up to maybe 100 psi, then they would be strong enough to not fail in normal use.

davidaf · 05-03-2015, 05:52 PM

I bought a metal one at Home Depot, I believe it's rated to 120 but that's no guarantee it won't fail as the O-Ring slipped and it ended up leaking after a few months. At least it was an easy fix and I knew where it was.

steelpony5555 · 05-06-2015, 05:26 PM

Even if you bypass it like I did it still won't work. Mine still makes lots of noise and I don't know how cause not much water is getting to the tank.

BB_TX · 05-07-2015, 04:16 AM

Mine actually does work. It also makes a lot of noise. But after draining the tank and starting the flush, I close the black tank valve while running the flush, leave the valve closed for at least one minute, open the valve, and quite a bit of water and more solids come out. Repeat 2-3 times each time I drain until water runs fairly clear. Before putting back in storage I do the flush thing several times.

twindman · 05-07-2015, 07:04 PM

I kind of time the flush. It takes about 4-6 minutes to get the tank pretty full. Then everything come cascading out the drain and things get cleaned.

Metamorphosis · 05-08-2015, 07:31 AM

My anti siphon/backflow valve was acting up, so I took it out and took it apart and noticed that there was some small debris sitting around the rubber ball underneath the spring. I talked to the supplier and they indicated that when Keystone is building the Rv's all kind of small wood chips and metal flakes are around the RV and sometimes they end up in the water line, which then can end up in the valve, causing an issue. Just one more thing to be aware of.

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