21NE tiny black tank

Your 30 gallon black tank is a whole lot bigger than a 13 gallon tank. Apples to oranges.
I never caught that. I went and looked. 13.8 gal, I do have to wonder why, must not really be room? Still, that is a fair bit of waste, I have no idea after 1 week how much volume is in my tank, I just know there is plenty of room left and I go and dump. ;D

For us it definitely is the grey tank volume and we do lots of things to minimize how much grey water we have to store. Still, we survive.....barely. :cool:
 
While certainly possible, I would think installing a larger/custom black tank would be a daunting task. The entire bathroom and driver's-side dinette area might have to be disassembled...as well as various other systems relocated to make room for a larger tank.

If a secondary tote tank isn't an option, It might be less intrusive to look at converting to either a composting or incinerating toilet. These would either eliminate the need for a black tank or limit use of the black tank to liquid waste only.
 
IMHO, 10 gallons is a lot of business for two people. Even on a long weekend, we never come close to filling up the black tank. The grey tank is the limiting factor. In fact, I don't think you want a bigger tank unless you are sure you need it because the 10gal tank in there flushes and drains very fast and very clean. If you put in a larger tank, it's likely to drain slowly and incomplete, which can be a real pain to flush out each time you dump.
 
If you put in a larger tank, it's likely to drain slowly and incomplete, which can be a real pain to clean out each time you dump.

Unlike the grey tank, the black tank has an elevation change and a much larger cross-sectional area so it's still going to drain fairly well.

A larger capacity tank would take longer to drain but not by much. Yes, the longer the tank the more likely there's a pyramid to deal with. :rolleyes: We routinely dump a bucket or two in to move things along.

Ron
 
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We tend to use some dish water in the black to add moisture and keep it out of the gray. Unlike some here, we are not a fan of the outside dish washing station, but that also works for some.
 
Tiny black tank update

Update: I have thought about adding a second tank adjacent to the existing one which projects into the space under dinette bench. There is room to add another tank. The project would include adding tank flush fittings to both tanks. The second tank would have its own outlet. Please see attached sketch. All input appreciated.
 

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Hate to be negative but I think that design would be problematic given the nature of the contents.

I think that the connecting pipe between the two tanks would cause the solids to settle out just before the exit of the first tank and concentrate them in the one area.

Clearing an area of concentrated solids might be more trouble than its worth.

But who knows for sure.

Ron
 
Well, you're apparently seriously motivated to increase your on-board black tank capacity!

Looking at the sketched proposal, it seems to me that by the time you go through all the effort and additional connections (each a potential leak point for waste or odors, IMO) you would just be better off cutting out the OE tank and installing a single custom tank to meet your specs.

That could likely be fabricated to match the OE toilet, vent, and outlet, and add a 'flushing hose' connection if desired, all with factory welded fittings of the most robust and high-integrity type.

Given the bath module similarities, one might wonder if the 30-gallon black-tank ETI installs in the 5.0 (which extends into the front jack compartment) might work?

Yeah, the idea of multiple-black tanks with interconnections inside the trailer (at least one of them being a 'field-installed fitting') and multiple dump outlets just strikes me as an undesirable long-term arrangement, worth working very hard (and perhaps paying 'extra' for) in the short-term to avoid.

Not suggesting this would be 'easy', but I'm confident it's do-able working from the bench area without disturbing the molded fiberglass bath module and would be a much more desirable arrangement in the long run.

IMO if you're driven to solve this 'problem' with out of the box 'solutions', it should be done 'right'.

Just one opinion for your consideration, Good Luck!
 
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Crow’s Nest, I think your design would work as it is quite similar to the design of a septic tank with two connected chambers. In a septic tank the connection is via a baffle that leaves a wide opening between the chambers. The concern with your schematic is the size of the connecting pipe so that it doesn’t get clogged with paper. The larger the connection the better. (Your schematic isn’t a septic tank because in a septic system tank 1 is only pumped out every few years, not drained every 7-10 days.)

Dumping the tanks regularly and using the rinse hose should avoid sludge building up. Also you need to vent the tanks.

That being said, I would look at the one larger tank option. The connection pipe introduces a potential point of failure. And I think it would be inconvenient to have to jockey the trailer around to get to both dump valves.
 
One bigger tank sounds like a good idea.

Do you have space underneath the trailer to add another tank? I added a 13 gallon external tank in 2007 on my 17b because the black water tank is only 7.5 gallons, which was a bit small for the four of us. Tank venting and a new plumbing manifold to link the grey, black and added tanks together was the hardest part.

The mod is described on this link https://www.fiberglassrv.com/forums/f56/escape-trailer-auxiliary-tank-30273.html

The added tank has worked well for 17 years but a few years ago I added a metal, adhesively bonded, cover to improve road hazard protection and improve the tank mounting.
 
Update: I have thought about adding a second tank adjacent to the existing one which projects into the space under dinette bench. There is room to add another tank. The project would include adding tank flush fittings to both tanks. The second tank would have its own outlet. Please see attached sketch. All input appreciated.

What you have drawn out is a basic residential septic system where solids fall into the first tank and liquids move on to the second tank and then on to the leach field. Only you do not have a leach field. Solids would have to be pmped out of the first tank rather than drained. IMHO, not a good design for an RV.
 
Oh well. Back to the drawing board. Meanwhile the tote tank works fine. Thanks for the reality check.
 

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