Residual Black Water

[kedinger]

Hello and Happy Thanksgiving,
We are fairly new to RV-ing and learning as we go.
We have a Montana 3123 RL year is 2024.
We have an issue with the black water seemingly not to drain completely after you have drained it. We drain both gray water tanks after the black water and wait till nothing else is coming out. After we drive to the next destination and open the cap about a cup and a half of black water comes out. The dealership tells me that this is normal because of the configuration of the plumbing.
Hard for me to believe.
I’ve tried flushing the black water tank three times till nothing else comes out and it runs clear. But after we get to our next destination, same thing happens. I take the cap off and about a cup and a half of Blackwater comes out with some pressure.
Any experience/knowledge of this would be great.
Thanks

KC

[Gonefishing]

That’s about normal after moving around the water gets in the pipes

[Mikendebbie]

I don’t think my tanks drain to the “bone dry” point.
If you look at the sketch below - some tanks are located in the drop-frame section and some are located in the upper/main frame section. The discharge point (where you hook your sewer hose up) is well below the upper tanks and slightly below the lower tanks. The upper tanks will always drain better.

The tanks on my rig that are in the main frame are higher and gravity helps drain those MUCH better than the tanks located in the drop frame.

There are many YouTube videos “Keystone Montana factory tour”. In one of them, the factory rep suggest raising the front end of the fifth wheel to help/encourage those tanks to drain better.

[jsb5717]

Yep, totally normal. I find that one of these is a life saver. It allows you to connect your sewer hose without opening the pipe. You wait until you're ready to dump tanks to open this valve. In the meantime it prevents the little spillage when trying to connect.

This is on my sewer pipe full time.

https://www.amazon.com/Camco-Adapter...=sr_1_5?sr=8-5

[kedinger]

Originally Posted by jsb5717

Yep, totally normal. I find that one of these is a life saver. It allows you to connect your sewer hose without opening the pipe. You wait until you're ready to dump tanks to open this valve. In the meantime it prevents the little spillage when trying to connect.

This is on my sewer pipe full time.

https://www.amazon.com/Camco-Adapter...=sr_1_5?sr=8-5

Problem solved !!
Looks like a great suggestion.
Thank you.

KC

[DutchmenSport]

If you get a "Flush King" version, it comes with the clear section of pipe so you can actually see what is being discharged.

Click here.

Also, if you use one of these (either the one listed above, or the Flush King version), you can "back flush" your grey water into the black tank and flush it out WITHOUT having to use your black tank flusher and extra water.

If interested in the process, I'll add the steps how to do it. You do need the 3rd valve attached at the discharged port though and both black and grey tanks need to discharge from the same port.

[scottz]

Welcome.

That is normal. As suggested, you need to put a gate valve on your drain. Valterra is a good brand.
https://www.amazon.com/Valterra-T58-...s%2C183&sr=8-3

You also need the gate valve for other reasons. If one of your tank valves leaks a little, the gate valve will save you from getting a face full when you remove the cap; you will thank us later. I bought a flush king, but it does not work well for me, sitting on a shelf. The configuration of my plumbing keeps the "jet" of water from going very far. I keep one of these attached to my drain how to monitor the process.
https://www.amazon.com/Valterra-T102...2&sr=8-43&th=1

Dumping: I use the black tank flush, close the tank valve and put 20 or so gallons of water in the tank, dump it, repeat until clear. NEVER walk away or get distracted when using this method; get one of these
https://www.amazon.com/Save-a-Drop-P...s%2C213&sr=8-7
or let the water run for 3 minutes or less; set a timer. Do not over-fill the tank; you will not be happy. When I want to drain the tank completely, I elevate the front end of the RV (the drain is on the rear of the tank), but normally only do this when I'm going into storage or need to work on the tanks.

One other thing; we have a bidet and do not put paper in the tank; it is hard to get out. Your call.
https://www.amazon.com/Luxe-Bidet-Ne...s%2C194&sr=8-7

[Bourbon County]

I believe we've all had that very embarrassing moment when we took the cap off the drain pipe and got some spillage. If you're parked on a concrete pad, it is be a good drill on how quick you can get the water hose hooked up! I'm in 100% agreement with either the Camco or Valterra last resort valve.

There are glue on models on the market that are in my opinion even better. I've had mine try to release from the bayonet locks while removing the cap which is really bad too. Just take a Dremel and buzz the little nubs off, sand it smooth and glue the valve on with some ABS cement. They are supposed to be installed with the handle between 9 and 3 o'clock position, the closer to straight up the better, never install with the pull handle down. It seems like the locking nubs are always never quite in the right position for the twist on models. Should you ever need to service or repair it, they are bolted together and can be disassembled.

[scottz]

Had the same issue. I put a large hose clamp around the locking fingers; it does not move anymore.

[twindman]

I put one of the clear connection valves on a long time ago. I believe I put a small screw thru it so it doesn't come lose when you remove your drain hose. Works great.

[Daryles]

If you really want to get the black and forward grey tanks empty, raise the front as high as you can Tilt the rig left a bit then dump and flush.
For the galley tank level the rug and Tilt it left.
I do this to get the tanks empty for winterizing.
Buy a gate valve to prevent surprises.
Our black tank valve leaked from the first day we bought ours. I finally dropped the front coroplast and replaced the back tank valve seals. Not a hard job. I added insulation around the frame perimeter and across the bottom before putting the coroplast back up.