Sludge build up in 1 1/2 bath fifth wheels

[grampyjd]

My wife and I have been RVing for over 30 years in five different motor homes. Our last motor home had a bath and a half with four tanks, two black and two gray. When we would dump, it would take 10 to 15 minutes to drain and flush all four tanks. Last year (2014) we decided to try a fifth wheel while we could still travel.

In March we purchased a new 2014 Montana 3900FB, bath and a half, fifth wheel. After a short trip our front tanks wouldn’t drain and the service department said we didn’t use chemicals, which we did. Having RV’d for 30 years we know how to use chemicals, flush and drain tanks. My concern is the front two holding tanks on the fifth wheel. With clean water I filled all four tanks 1/3 full and then I drained each into a 5 gallon bucket one at a time. The front black tank took 25 seconds to discharge 2 1/2 gallons. The front gray tank took 20 seconds to discharge 2 1/2 gallons. The back black tank took 8 seconds to discharge 2 1/2 gallons. The back gray tank took five seconds to discharge 2 1/2 gallons.

My concern is with the slow rate of flow from the two front tanks, especially the black tank, am I apt to continually run into problems with sludge accumulation. Has anybody out there had problems draining their tanks on the Montana 3900FB fifth wheel. (or on any bath and a half fifth wheel).

Thanks for any help and comments.

Grampyjd

[Bumpyroad]

put in a black/grey tank sprayer to get rid of sludge build up.
bumpy

[laknox]

Vents have also been known to drop into the tank, preventing easy air entry. Since the vent should have a clear path right to the bottom of the tank, if you measure the distance from the top of the vent to the floor of the tank and compare it to the distance from the top of the vent to the bottom of the pipe (you should be able to hook the tape on the bottom of the vent pipe), and, if it's not more than a couple inches, then you might have a vent issue.

Lyle

[Old-Biscuit]

grampyjd wrote:
Thanks, Great suggestions. I'll look at Montana owners forum and check all the vents. How would I know if the cutouts are in the tanks without tearing things apart? Would a sewer guy with a camera be able to look in the tanks.

Grampyjd

Yes....camera

BUT first rule out the obvious.
Clear Vent to roof (run a garden hose down vent then blast away with drain valve open
Check for Air Admittance Valves

Then camera up the drain line thru dump valve. (Valves fully opening?)

[grampyjd]

Thanks, Great suggestions. I'll look at Montana owners forum and check all the vents. How would I know if the cutouts are in the tanks without tearing things apart? Would a sewer guy with a camera be able to look in the tanks.

Grampyjd

[Old-Biscuit]

Black tank has to have a vent to roof.
Grey tank should have a vent to roof along with an 'Air Admittance Valve' on sink drain line after the 'P' trap. It allows extra air into drain line when dump grey tank so 'P' traps don't get sucked dry. It is screwed int a sub pipe usually inside sink cabinet.


Also.......
The 'cut-outs' on those two waste tanks may have been left in tanks. Cut-outs are discs left from cutting access holes for pipes into tanks. They can fall into tank and should be removed by 'assembly line tank guy'.
If left in they can get sucked down to drain outlet opening, stick/obstruct flow.

Just something else that can cause drain flow issues.

[BB_TX]

Go over to the Montana Owners Club (MOC) forum for all things Montana. Lots of friendly helpful folks there with lots of Montana experience.

[grampyjd]

I didn't notice vents on the roof. I'll check them out if I can find them. Will there be one for each tank?
Thanks for a great idea and a starting point.

[Shrek51]

It sounds like the vent is not routed properly or not large enough.