Black Tank Capacity?

What does the manual say?

Specs listed show 40 gallons for all tanks


How did you determine you can only put 20 gallons in before black tank is FULL?
Surely NOT by 'level monitor/gauge'

Steelhawk wrote:
I have a used Trail Bay 27DS, 2007 model. I can only put 20 gallons in the black tank before it is full. I thought the black, gray and fresh tanks were all 40 gallons.

Am I incorrect or is my trailer somehow different than some brochures I found.

If it really is 20 gallons, how easy is it to put in a 40 gal tank?

Call Trail Bay and ask for customer support then ask them.

djgarcia wrote:
Call Trail Bay and ask for customer support then ask them.

Hardly ... the OP's Trail Bay was manufactured by R-Vision which has been out of business for several years now. :R

If specs for the OP's Trail Bay says it has a 40 gal black water tank then that's what it has ... unfortunately he hasn't provided any detail at all as to why he believes it's full with just 20 gals. :R

In the OP's defense, mistakes have been made in the past, especially in RV manufacturing. I can't imagine a 20 gallon tank for anything on an RV... but it is conceivable that a manufacturer made a boo boo and installed the wrong size tank.

The more likely theory is that the OP is using an incorrect method to fill his black tank or simply is underestimating how much water is coming out of the tank when he empties. I've never measured the water and "stuff" coming out...

spoon059 wrote:
The more likely theory is that the OP is using an incorrect method to fill his black tank or simply is underestimating how much water is coming out of the tank when he empties.

The OP was unfortunately not clear at all as to how he determined his 40 gal tank is only holding 20 gals but if I had to guess it would be that he's relying on that silly tank monitor which as anyone who has been at this for awhile knows will almost always read tank content inaccurately. This is all speculation for now though, until the OP clarifies. ;)

Just a guess but an obstruction could be holding back half the tank contents while dumping. I would poke something in there from one of two directions and determine if it's dry. Also it's easy to determine the capacity of the tank by dumping measured water from a bucket through the toilet and into the tank.

I measured going in, three gallons at a time, doing a visual inspection of the water level after each bucket full. The specs say 40, but I can only put 20 in it before it will overflow into the trailer.

And, as gross as it sounds, I measured the volume of what came out. It had been flushed a bunch of times, so it wasn't too yucky.

The reason I'm doing all this is because on our first campout, the black tank filled up after only day of use and I had to visit the dump site. I took it back to the dealer and they said it seemed to have had some old stuff in it, but was now flushed out, however, it appears to only hold 1/2 of what the specs say.

Being new to this, I'm not sure what to do next.

One more thing. Unless I'm understanding wrong, the tanks are mislabeled on the outside. The gate that says "Body Waste" is the gray tank. The one that says "Liquid Waste" is the black tank. Of that I'm sure.

Steelhawk wrote:
One more thing. Unless I'm understanding wrong, the tanks are mislabeled on the outside. The gate that says "Body Waste" is the gray tank. The one that says "Liquid Waste" is the black tank. Of that I'm sure.

You "sure"? Regardless of the labeling the black water valve will have a 3" blade, the grey will have a 1.5" blade.

No way a travel trailer the size of yours would have just a 20 gal black water tank ... it's a 2007 model and if the tank isn't draining properly it's either clogged or the tank itself has developed "pyramids of poo", which is not uncommon at all if the owner is in the habit of leaving the waste gate open all the time rather than closed as it should be.