Black Water tank fully drains only when driving

[Ike Shipley]

I have a 2020 3950fl we started noticing last year that the black water tank does not fully drain at the dump station. The black tank only fully drains the remaining 1/3 of the tank when driving and bouncing around. I’m confused as to why it would drain part of the tank but not all of it. And how driving and bouncing would cause it to flow. It’s as if the draining isn’t properly sloped. Does anyone know the cause of this or have a diagram of the 3950fl pluming and/or tank drainage system?

 

[travelin2]

None of our tanks drain to the point of totally empty, even if the door side of the rig is elevated.
The outlet is not even with the bottom of the tanks and the tank bottom is not flat and bows down below the outlet valve
I removed a grey tank for repair and it’s quite evident that they can never drain completely while sitting on a campsite or dump station
I don’t have a photo of the tank’s profile to substantiate my remarks but it’s the truth

 

[Ike Shipley]

does heartland have any drawings or cad designs showing the plumbing or tank layout like the attached image but for the 3950fl??

 

[Roller4tan]

The vent stack for that tank may have fell further into the tank, not allowing air flow into the tank while dumping. If you take the cap off the top end of the pipe should be at roof level. If you flush your toilet while dumping and more liquid dumps, then the stack is plugged.

 

[Ike Shipley]

I took off the vent caps, filled up the black tanks full with water, stuck fish sticks down the each of the black tank roof vents, the fish sticks went straight down with no resistance and were wet when I pulled them out. So the vents definitely aren’t plugged. So back to step one. Is there any possible other causes as to why most of the black tank immediately drains most as soon as i pull the valve, however the remaining of the black tank doesn’t come out unless I’m moving and allowing it to gush out a little(2-3 gallons) at a time whenever I hit a bump.

 

[travelin2]

If you are expecting all the poop to exit the tank on an initial “pull the handle & dump”, it ain’t gonna happen.
Do you flush the tank during your dumping process? Solids sink to the bottom and aren’t coming out without some persuasion and that means water & lots of it

 

[Ike Shipley]

Right. Every time I drain the blacks I hook up water to the tanks and flush the water through as it’s draining. I’m just not understanding why it does not completely drain unless the rv is moving and bouncing.

 

[rhodies1]

Pick yourself up a Vulterra Flush King and backflush from the discharge pipe: This is the best piece of equipment I’ve purchased for my unit,I never use the built in flusher anymore,they are not even close to the flush king for cleaning your tank.

 

[Ike Shipley]

I already have one of them. So you’re thinking the pipe is plugged? I’m confused as to why it would be letting some of the tank out if the pipe is plugged

 

[Ike Shipley]

Hey Et1958!! Thanks for the heads up. You must have been an environmentalist. Gotta love a good whistle blower. The world needs more guys like you to advise guys like me who are walking around clueless and had no idea it would be unlawful to dump black tanks on a highway…..I own 8000 acres pasture and farm land. Driving or parked, It is not UNLAWFUL to drain black tanks on privately owned pastures or fields. After all, where do you think animal wastes send up and fields are exactly where the pump trucks drain the wastes it’s removed from the dump stations. But once again thanks for going out of your way to help us and shine your light.

 

[rhodies1]

no I doing believe your pipe is plugged but using the Velterra drives water against the outlet pipe pushing everything back into tank and allows you to get a lot of water into the tank in a hurry, keep all other drains close closed. fill up your black using this method.
The factory installed black flush doesn’t have a lot of water splashing around to clean,using the ,Vulterra it will clean good and if you have a poop pyramid build up near the discharge pipe in the tank,this method will break it down clean better. Try it and see if you get better results.
I used to use the factory installed black flush and thought I was getting everything out but eventually was having issues getting tank to drain. Not anymore ..using the back flush method could not believe the stuff that came out when I started using it .......

 

[Ike Shipley]

Ok. I’ll try it today and see if it helps. Thanks.