Basic Plumbing Question

bhecker129

Member
Joined
May 11, 2025
Posts
15
Location
Haines City, FL

Montana 3400 RL from 2009​

Hi I bought this model used (that I believe was from 2009) and it did not come with a user manual. I bought a standard sized Revolution brand sewage hose but it is not compatible with the 5” sewage outlet diameter coming out of the 5th Wheel. In my research it said the 5th Wheel should been 3”’standard but clearly it is not. Can you help me with a diagram of the plumbing underneath (or lead me to where I can find the manual online) so I know what I’m doing as well as what kind of adapter one needs to buy for my sewage hose. Thank you!
 
I did a quick search on Keystone website and did not find your specific rig. You might try a more extensive search, if you haven't already.
I do know rv waste water systems use ABS piping. The final outlet is 3" (almost always) with an adapter for the quick connect hose assembly. There is no such size of 5".
Sounds like there has been some odd adapter installed on yours.
A picture would be helpful.
 
Your 2009 3400RL (one of the most popular models Montana ever built!) came with a standard 3" ABS coupling like any RV. If there is a 5" coupler, then a previous owner modified it.

As for a User Manual, what Montana supplied was basically worthless. Here is a link to a 2005 User Manual which you can download. Click on the following link, then Click on the "Download" button in the upper right corner.
 
Thank you guys for your help!

I got a good deal on the Montanna 3400RL ($9000) but of course it does have its problems (for example, the air conditioning doesn’t work in the bedroom, the awning is broken and won’t extend, the microwave light won’t go off, the front levelers didn’t extend when switched on, but beggars can’t be choosers!) I finally got it level with some help and some heavy jacks, I have the electricity and the water working fine, but I’m still about 5 days in without any plumbing hook up. I’m a total newbie to all so this will all be a big learning experience for me. I’m excited though to learn what I need to do to enjoy it, keep it in good shape and maintain it. I intend to live in it for a few months at least, maybe up to a year in this small RV park in Central Florida.

After visiting a Camping World store that specializes in Montanas, and before receiving the last message, I also learned that the 5-inch diameter pipe was actually an extra connector meant to link to the original 3-inch output pipe. This is what really caused me to be stagnant for days. Apparently, a lot of folks complained about it according to the guy at the Camp World store, so I’m just going to bypass it and go straight to the 3-inch pipe. The guy there also sold me an elbow piece that will connect to the standard Walmart Revolution sewage hose I previously bought and then into the ground.

On another note, I found digital manuals for 2005 and 2010 models on the Montana site. Since the original owner registered in 2009, I’m thinking it might actually be a 2010 model(?)

I’m still trying to figure out is the exact location of the grey and black water tanks and the lever placements. The manual doesn’t have clear diagrams. Do you guys have any suggestions on where I could find good visual guides or diagrams for where everything is?

Thanks again for all your help!
 
Not back to my site yet but these are all my elements as of now:
 

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That old sewer hose looks like clothes dryer vent pipe. It looks like it is attached with a worm gear clamp commonly used on dryers.Some body was really creative. Your on the right track, cut that crap off back to the 3" and install the proper adapter. You'll be in business.
Sorry, can't help you with the tank locations, I know someone here probably can.
 
Your black 5" pipe with a cap on the one end is a storage tube for the 3" sewer hose. Some owners may have taken that storage tube off to store their hose someplace else. I changed out that short tube and purchased a longer tube in order to have a 10' sewer hose. I added additional support to the one end so that it would not sag or bounce when traveling. I prefer the hose being stored in the tube rather than in the garage some place.
 
Here are some random thoughts related to your 3400RL

Montana used a sewer hose storage tube mounted along side the frame. There was/is a 3" standard sewer hose inside the tube. The tube would swing out so it you could dump. The 3" hose was/is connected to the standard drain outlet. That 5" flexible hose from the tube to the drain output is merely decoration. It serve no purpose. Most of us removed it. The end of the sewer tube is a twist off cap which gives access the output side of the 3" hose inside. Remove the cap and pull out the hose to connect to the park's sewer drain. I store my 12" hose in that tube (obviously collapsed).

The Walmart hose does not have a 90 degree air tight connector required to attach to the park's sewer drain. The CW guy did you a solid (albeit slightly overpriced) with the adapter. My preference would have been to buy a Rhino hose, which comes with the 90 adapter, but the Walmart one will work for a year or so.

There are three storage tanks on a 3400RL. One black, one for the shower, and one for the kitchen. They are all mounted perpendicular to the length of the RV (i.e. across the main frame). The black and shower tanks are located under the pass through compartment. which one is closest to the front of the RV differs depending on the RV model. I don't remember the 3400RL layout. But a quick look in the pass through compartment will show where the toilet and shower drain lines come down and into the tanks. That should help. The drain handles for those two tanks should be labeled but given the age, may be unreadable. As the valves exit on the drivers side end of those tanks, you will know which is which after looking at the drain lines. The handles for those two tanks come directly out in the lower portion of the pass through compartment. The kitchen tank is above the axles and the drain handle sticks out from the frame on the drivers side in front or near, the wheels. Hopefully the handle is still there. If not, it is relatively easy replace it. There was a similar discussion a year or so ago. A Search may help you find it.

The front jacks are pretty simple to diagnose and repair/replace. The awning is yet another relatively easy device to repair. The microwave (tell me it isn't an Apollo?) might be better to just replace. I suggest your start separate Threads for each item so we can help you with stumbling over different problems.
 
Thank you! Yesterday, I evolved the mission but I’m still having some issues. I attached a hose to the 3” output and then to the ground, the problem is that my valve handles on the black and grey tanks are almost impossible to move. I finally got the black one out (yes, I made sure to pour enough water in the toilet first + a splash of the liquid concoction I got at the RV store that breaks everything down) and then struggled to push in the black valve again after the flush but I did, but the grey one is completely stuck in the open position. I thought I would be fine with that until I saw my tank levels which showed one grey tank empty and another one full. And the black tank still shows it is 1/3 full (I did read a few times that these can be deceiving because of sensors reading artifacts stuck to sides of piping?); regardless of that, 1) how urgent is it for me to replace the one stuck open gray valve, 2) the hard-to-maneuver black valve, 3) How do I officially determine if my black tank is all flushing or not/whether I need to repair something/or if I can accept sensors that don’t work great and just flush the black tank when it gets to 2/3, even if it only goes back to 1/3, and finally 4) Where the heck is the second grey tank valve??
 
Thank you! Yesterday, I evolved the mission but I’m still having some issues. I attached a hose to the 3” output and then to the ground, the problem is that my valve handles on the black and grey tanks are almost impossible to move. I finally got the black one out (yes, I made sure to pour enough water in the toilet first + a splash of the liquid concoction I got at the RV store that breaks everything down) and then struggled to push in the black valve again after the flush but I did, but the grey one is completely stuck in the open position. I thought I would be fine with that until I saw my tank levels which showed one grey tank empty and another one full. And the black tank still shows it is 1/3 full (I did read a few times that these can be deceiving because of sensors reading artifacts stuck to sides of piping?); regardless of that, 1) how urgent is it for me to replace the one stuck open gray valve, 2) the hard-to-maneuver black valve, 3) How do I officially determine if my black tank is all flushing or not/whether I need to repair something/or if I can accept sensors that don’t work great and just flush the black tank when it gets to 2/3, even if it only goes back to 1/3, and finally 4) Where the heck is the second grey tank valve??
 

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Is this the second gray tank valve?
 

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Given the recent photos, you have a 2010 model. I believe that is when Montana introduced the dropped frame and the convenience center. The description I provided earlier about the tanks and dump handles is not correct for your year.

The black and shower tanks run longitudinally, parallel to the frame. The kitchen tank is as I described previously. Perpendicular to the frame above the axles. The black and shower tanks have flexible cables that operate them. The operable end is there in the convenience center. The cables run to the back end of the tanks, where the valves are. It is common for those cables to get corroded and hard to move. And likely the valves and its gaskets are shot. They are not that difficult to replace if you are handy. A Search will uncover discussions about the process.

The kitchen tank has a 1 1/2" drain line that connects to the 3" drain pipe from the black/shower tanks. You can see it in the latest set of pictures you provided. The valve for the kitchen tank is, by code, installed close to the tank. It has a solid rod that passes through the frame and directly operates the valve.

1) how urgent is it for me to replace the one stuck open gray valve,
This one can stay open as long as you have a quasi "P" trap (i.e. a dip) in the sewer hose to prevent sewer gasses from coming back into the tank and RV.
2) the hard-to-maneuver black valve,
This needs to be fixed regardless of it is open or closed. If closed, then it will fill up and then you have problems. If Open, then the liquids drain and the solids build up and solidify. AKA the the poop pyramid. Yet another problem you don't want.
3) How do I officially determine if my black tank is all flushing or not/
The best answer is a clear extension attached to the sewer pipe. It gives you a clear picture of what, if anything, is coming out the pipe. When flushing the black tank it helps you to know when the output is clear and clean (as much as it can be). Amazon.com
whether I need to repair something/or if I can accept sensors that don’t work great and just flush the black tank when it gets to 2/3, even if it only goes back to 1/3, and finally
The sensors are notoriously inaccurate as you have learned. There are alternative sensors that live outside the tank that you can install - Seelevel Sensor https://www.etrailer.com/Smart-RV/S...vJRiXr0aRKs01_l6OKyfw8KEBtqohMoBoCcCsQAvD_BwE

Most of us just get used to how frequently the tanks need to be drained based on our usage. The toilet tank burps when close to full and the shower backs up when its tank if full. You don't want them to do that very often as it is hard on the tanks.
4) Where the heck is the second grey tank valve??
The handle to operate the valve comes through a hole in the frame or coroplast (depends on the model) somewhere around the wheels. It is not uncommon for it to be missing. Drop the edge of the coroplast and you can see the valve. The rod is 1/4" thread and easily replaced. I am pretty sure CW has them along with other places.
Is this the second gray tank valve?
That is a bracket that supports the kitchen drain line. The valve is further towards the rear where the tank is located.
 
Thank you Carl. I lot of useful info.

It sounds like you're saying the kitchen water tank (GREY 1) has the valve that is the hidden one, and the shower/bathroom sink (GREY 2) has the valve handle next to my black tank valve handle. That's the one that is stuck in an out position. Where I get confused is that my sensors are saying that my GREY 1 tank is empty now after the flush but my GREY 2 is 2/3 full.
 
I suspect Grey 1 is the shower and Grey 2 is the kitchen, But it doesn't matter, the gauges are crap. Once you have working valves and a clear connector so you can see what is flowing, you should be able to figure out which is which.
 
I would suggest when installing a clear outlet thiing, get one with a valve on it or get another optional piece that has the valve built in. Then you don't have to worry about your stuck open valve, other than having to dump that stuff immediately since it is always open.
Remember you are supposed to dump the black tank and then the gray tank to flush out the, ahem, crap left in the drain from the black tank. Since you will have the gray tank drained first because of stuck valve, you will have no way to do this.
Finally, I would put in a new valve system either yourself or a dealer. I think the good ones are the Valterra ones?? Others chime in here. They are much better than the original ones. I myself did not want to cut into the coroplast and work while laying on my back, so I paid the dealer to put in a new valve.
 
Two options you could do is to put a valve on the end of your outlet such as this:
or you could add a Flush King to the outlet which is an even better option that would allow you to back-flush the pipes after dumping:

Additionally, the flush king has a clear elbow as Carl spoke about that will allow you to see what is coming out while dumping.
 
Thanks for the tips. I really tried looking for the second gray tank valve based on your description, Carl, but I couldn't find it. I'm just too much of a newb here. I wish there was some picture that could show me, but Montana has no such thing and I couldn't find pictures when I searched the internet. Maybe it's buried in the wealth of info out there, but I couldn't easily locate it. Looks like I might have to get a technician to help me after all like twindman suggests.
 
You can find it. I know there are pictures of the valve handle here. I will try to find them later. But the key point is you are looking for a straight rod with a "T" handle protruding from the frame or coroplast in the driver's side wheel well area. It could be in front, between or behind a wheel..

It is not uncommon for the rod to unscrew and fall off. That makes it a tad more difficult. But so doable. Undo the coroplast in the wheel well area and find the valve. It is connected to the 1 1/2" drain pipe, so just follow it. Replacement rods are available.
 
Alright Carl! I appreciate you sticking it out with me. I’m going to include a bunch of pictures and you can tell me, like the children’s game, if I’m getting warmer or colder. I see one valve but in an earlier post you told me that was a kitchen valve.
 

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