Momentum Grey tanks slow drain

[gone AWOL]

Grey tanks both drain a trickle at best, been like that since new. I've read this is a issue on the momentum 376? Anyone found the problem?
I also suspect it's not draining 100%.

[plastictires]

My experience is that just about everyone has this problem. After a number of years of owner ship I figured out I have to raise the front end of the rig (a lot) to get a good flow out of the drains. And still some water remains in the tanks and in the drain pipes/system. The plumbing is just a bad design and likely exaggerated by the drop frame front. Some other manufacturers seem to do a better job, some are the same.

A lot of owners also add another valve at the end of the drain pipe to eliminate that small gush of water that gets sloshed into the end of the drain when driving so it doesn't dump on you when you remove the end cap.

[howson]

Grey tanks both drain a trickle at best, been like that since new. I've read this is a issue on the momentum 376? Anyone found the problem?
I also suspect it's not draining 100%.

I agree with plastictires (interesting forum name!). Many of us here have the Valterra Twist-On added to our trailers to avoid getting a "surprise".

Also, it might be impossible to completely drain the tanks on the majority of our trailers as stated in his post. Mine certainly don't.

https://www.etrailer.com/RV-Waste-Va...terra/T58.html



Get the cap, too, and you'll have a way to backflush.

https://www.etrailer.com/Accessories...T1020-1VP.html



Howard

[gone AWOL]

I have that valve already, eliminate surprises for sure. We are just so tired of paying a ton of money and have to accept sub-standard quality (I probably can't say "sub"standard as the "standard" is already below grade ....)
If it is (obviously) a known problem, why don't GD jump in with a recall, or a recommended fix, (yes that would unfortunately mean admitting to a problem)
If anyone has ideas let's try and solve this.....
(Does anyone have pictures of the open basement or of the hidden plumbing?)

[Cate&Rob]

(Does anyone have pictures of the open basement or of the hidden plumbing?)

Attached is a picture of the drain system on a Reflection. Yours will be similar. There is no "design" reason for a slow draining tank. There are lots of "installation" reasons for slow draining . . . ranging from the gate not pulling very far open when you pull the cable to a variety of blockages. A common one is the plastic disc that is created and drops into the tank when they use a hole saw to cut the openings for the inlet and vent pipes.

Note that the gate valve opening is not as low as the bottom of the tank. There will always be a half inch or more of liquid in the bottom of the tank unless you dramatically tip the RV fore/aft to empty this.

I have done some rather extensive modifications to provide opening doors in the underbelly, grease fittings on the gate valves to keep them easy to operate, pull cable re-routing, drain manifold connectors to allow the removal of a single gate valve without disturbing everything else . . . and so on. If you would like further details on these mods, see the plumbing reference section of this forum or I can provide pointers to specific topics.

Rob

[Hogdrv]

public service announcement...........

On the subject of the extra valve at the end of the drain pipe, I installed one on each of my sewer pipes; great idea love them, however just a warning ⛔️ that I was not aware of, the extra weight and bumpy roads will break the straps supporting the pipes. I snapped one of the straps in two and the back one was barely hanging on. So I recommend beefing up the straps at the end of the sewer pipes. Now back to the original subject

[gone AWOL]

Attached is a picture of the drain system on a Reflection. Yours will be similar. There is no "design" reason for a slow draining tank. There are lots of "installation" reasons for slow draining . . . ranging from the gate not pulling very far open when you pull the cable to a variety of blockages. A common one is the plastic disc that is created and drops into the tank when they use a hole saw to cut the openings for the inlet and vent pipes.

Note that the gate valve opening is not as low as the bottom of the tank. There will always be a half inch or more of liquid in the bottom of the tank unless you dramatically tip the RV fore/aft to empty this.

I have done some rather extensive modifications to provide opening doors in the underbelly, grease fittings on the gate valves to keep them easy to operate, pull cable re-routing, drain manifold connectors to allow the removal of a single gate valve without disturbing everything else . . . and so on. If you would like further details on these mods, see the plumbing reference section of this forum or I can provide pointers to specific topics.

Rob

Can you please tell me the orientation of that picture and if you could the approximate location in the chassis, front of axle etc.
I Trust that you have a drop frame?
Thanks for the picture, speaks volumes.

[Cate&Rob]

gone AWOL

The picture is taken crosswise looking towards the left/street side forward of the axles. The drain hose attachment point is at the bottom of the picture. A Reflection does not have a drop frame. The black tank is the closest on the right in the picture (towards the front of the trailer). Beyond that on the right is the shower grey tank. To the left is the crosswise galley grey tank. In the upper foreground of the picture is the smaller diameter (1 1/2”) drain from the galley grey. Your Momentum won’t likely have any drain lines/valves smaller than 3”.

Rob

[Country Campers]

I wonder if d2reid has any pictures or ideas of what the cause may be.

I can let you know that all of the holding tanks are oriented lengthwise across the trailer starting with the black tank which is right under the toilet, then the bath grey and then the kitchen grey, moving forward. The only thing that I can think of is if one or more of the whole cut outs for the tank inputs where left in the tank or tanks and are plugging the output. It does not seem that there is any long runs of pipes from any of the tanks. The kitchen grey connects to the bath grey and then to the black and then the outlet pipe. If you contact GD Customer Service they should email you a holding tank layout so you know what you are looking for, you will not be allowed to post or share this info though.

Brian

[d2reid]

I typically do not have any problems with draining my tanks. Of course the gauges don't work so it's kind of hard to tell for sure. If the left rear of my 376 is lower than the rest of the RV I get a better drain. Normally there is a huge gush when I open the valves. Lasts for a minute or two, then it will trickle for a while. Unfortunately you have to drop the bottom to get a good look at what is really going on. I don't try to get a complete drain on the tanks. It's my belief that a little left in the bottom while you are traveling helps break things up and makes draining better.

One of my gray water check valves does not work correctly, I forget which one, I open both gray valves at the same time and it drains ok. My black water valve has a little seepy leak, I'll get a couple of cups of mostly water against the outside Valtera valve. If I can get it into a shop for some major repairs I will see if I can't get that valve replaced, but since I can manage it I haven't made the effort.

Here is a diagram that I found of the holding tanks in my 2017 Momentum 376. Sorry I don't have more. Wait - of course I have a funny story...

This last summer we stayed at an RV park that did not have sewer hookup, we had to hire a pump out service or hook up and dump. I hired the service. I like to be around when folks work around my RV, so I got to know the pump guys pretty well. One day the pump out machine started to pull down really hard, there was a clog in the pipe. He shuts it down and starts to investigate. We find a tube of joint pain cream stuck in the 90 degree elbow, its about the size of a tube of toothpaste. Apparently this tube dropped into the toilet while it was flushing and quickly disappeared down the pipe into the tank. It sloshed around for several months and the only way it was coming out was when the pump out system applied suction to the tank.

[howson]

d2reid -- I removed the GD drawing as per their rules (it's their forum) GD drawings are not to be posted. (Posted here in lieu of a private message so others know why the picture was removed. Thanks for understanding.) -Howard

[JBill9694]

I agree with d2reid that there should be an initial gush when the drain valve is opened. If this isn't happening, then I agree with Cate&Rob that either the valve is not opening all the way (the cable handle should move about 3" when the valve is opened) or that there is an obstruction. Have you tried backflushing the tank, being careful not to overfill it? Or even snaking the drain line, doable since it is the grey tank that's causing the problem.

Unless the obstruction is removed, backflushing and snaking would be temporary solutions, but if either works even temporarily that would provide proof of the problem. The only sure way to remove the obstruction would be to pull the valve off the end of the tank and go sniggling. At least it is the grey tank.

[gone AWOL]

I agree with d2reid that there should be an initial gush when the drain valve is opened. If this isn't happening, then I agree with Cate&Rob that either the valve is not opening all the way (the cable handle should move about 3" when the valve is opened) or that there is an obstruction. Have you tried backflushing the tank, being careful not to overfill it? Or even snaking the drain line, doable since it is the grey tank that's causing the problem.

Unless the obstruction is removed, backflushing and snaking would be temporary solutions, but if either works even temporarily that would provide proof of the problem. The only sure way to remove the obstruction would be to pull the valve off the end of the tank and go sniggling. At least it is the grey tank.

Gents,
My 2022 Momentum 376THS is equipped with 1 black and 2 grey tanks, thus two pull handles to open the grey tanks.
BOTH the grey tanks do the exact same thing, trickle to empty.
The handles pull a full 3"ish. Even if pulled at the same time does the flow not change.
I am going to try and snake them, but when the trailer was severely angled front to back the flow was almost normal.
I think, like most of my issues to date on this unit it comes to workmanship, poor workmanship.
I'll keep you posted.

[d2reid]

BOTH the grey tanks do the exact same thing, trickle to empty..

Do they blurp?

Ya'all can laugh at my phrasing if you want. But if the vents are blocked or the check valves are not working properly that's the sound you hear when you open the valves. And while I really don't think that is gone AWOL problem, it might be and worth a look.

[Jlawles2]

I think the recommended slope on drains is 1/4" per ft. So on a 16' run of pipe, there should be 4" of fall. This can be hard to accomplish in a camper as the tanks are typically close to or resting just about the bottom of the frame line. Now stretch that drain to the exit point and you could be well below the bottom frame rail. Add to that trailers are getting longer and more complicated with plumbing.