Black tank mounting

pennuja · September 17, 2017, 07:02:13 PM

My 4104 only has a single holding tank, for many reasons I would like to add a separate black tank.

The only location I have open that is right under the toilet is also right above the generator. Does anyone know how close the holding tank can be to the top of the generator. I have a Onan Emerald series generator and I am looking at plastic tanks. The plastic tank would almost (within an inch or two) touch the generator top cover.

TomC · September 17, 2017, 07:52:14 PM

First off, your gravity toilet does NOT have to be directly under the toilet. My 45gal black tank runs length wise down the center of the bus, but my toilet is mounted next to the wall on the right side wall. I have about a 3ft run from the toilet to the tank. By first filling the bowl with water like about what your home toilet has, I have had no problems flushing #2. So look for another spot away from your generator. Good Luck, TomC

eagle19952 · September 17, 2017, 10:20:48 PM

My terlet and it's tank are 4-5 feet apart.
the tank inlet is on the side. 4" pipe. drop is maybe 3/4"
been using it since 2003
installed by PO about 1996,to answer your question..i would say no, don't do it regarding proximity to your gen.
mine is 3 inches away parallel to my gen, but there is a walled insulated sandwich of 3/4" ply and 1 1/2 of insulation and soundproofing...

Zephod · September 18, 2017, 01:58:19 AM

Above the generator could lead to hot, bubbling poo and lovely poo aromas percolating deliciously through the bus.

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chessie4905 · September 18, 2017, 03:48:09 AM

I wouldn't recommend that location. Heat could cause plastic tank to eventually fail, potential fire hazard, and heat from generator will cause great increase of sewer gas production, possibly leaking into interior of coach.

pennuja · September 18, 2017, 04:22:43 AM

Thanks guys, I figured it was a bad idea. Good to know about the distance, I will look elsewhere.

Oonrahnjay · September 18, 2017, 04:43:56 AM

Quote from: eagle19952 on September 17, 2017, 10:20:48 PM
My terlet and it's tank are 4-5 feet apart.
the tank inlet is on the side. 4" pipe. drop is maybe 3/4" ...

I think that Don has included an important factor here. I was working with a guy who was putting an office with rest room in an old warehouse. He wanted to put in a direct toilet drain that would have been a drop of about 1 foot down for every foot side measurement. A guy who was helping with the drywall had had some plumbing experience before he retired was adamant about not doing that. He said "there's a perfect drop for a toilet drain pipe if you have to go sideways -- of course, you never want to go "uphill" but if you have too much drop in what's a basically horizontal section, the flushing water just rushes right by the solid contents and leaves them to just sit there and harden and cause a blockage. If you're almost flat horizontal, the flushing water pretty much floats the solid material along and keeps it moving." It would seem to me (not having a lot of experience with designing these kinds of things but following the "other old guy's" advice), that one secret to the success of Don's system that there's only a little bit of downward angle and that's working just like the guy told us it would.
If working to this principle is correct, then it's good news for us when we're dealing with limited underfloor height dimensions in a bus's bays -- the toilet drain, if it can't be a "direct vertical fall", should not run diagonally down across a bay but can be tucked up with only a slight drop angle against the underside of the floor.
This is only one word-of-mouth piece of advice so I'd appreciate other people's knowledge on this but it seems like something that could be considered. Anybody else got any info on this??

gg04 · September 18, 2017, 09:19:20 AM

Our bus has about 1/2" for 6' run. For commercial and RV parks we used under 2" per 100' for feed and under 1" per 100' for field.
4" pipe is great for 4 bedroom house, or tying a run of spots together, but small house, bus, or RV spot only needs 3" to keep volume of water under poop...

Zephod · September 18, 2017, 09:29:49 AM

The problem with shallow angles is that when parked on slopes, the angles could run backwards.

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richard5933 · September 18, 2017, 09:45:55 AM

Jim - What's the reason for upsetting the apple cart and adding the extra tank? Our coach is an older conversion and we only have one holding tank, black & grey in one tank (which of course makes it a black tank). It's plenty large, so I decided to just run with it as is.

Since the toilet is directly over the existing tank, if we were to split at some point in the future into two holding tanks I'd probably swap the current tank for a slightly smaller black tank in the same location, and then add a new large tank for grey water. Seems much easier to route grey water to a remote tank than black. This way I'd be able to maintain the current toilet-over-tank situation.

Richard

Scott & Heather · September 18, 2017, 02:09:58 PM

Zephod brings up a good point. If you're going to go easy with the slopes, you'd better be leveling your coach every time you park.

I'm also with Richard here, I have a 150 gallon combo tank and it works perfectly. No need to waste space and money and time with separate tanks. I have a diverted valve that I can turn on the main grey water drain that everything goes to so I can dump it into the combo tank, or straight on the ground or into one of my hose connections when I'm connected to sewer and I just use a WYE to run the grey into the sewer connection. Easy peasy. And you never have to worry about things getting a bit too sludgy in the tank because you're constantly diluting your solids with liquids from the kitchen sink, bathroom sink, and shower.

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gg04 · September 18, 2017, 05:03:24 PM

Quote from: Zephod on September 18, 2017, 09:29:49 AM
The problem with shallow angles is that when parked on slopes, the angles could run backwards.
Lol... to get mine to run backwards would take an angle past 60 degrees downhill ....not gonna park there .a...Thanks rdw

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pennuja · September 18, 2017, 05:07:13 PM

Thanks for all of the info.

My reasons for wanting to add the black tank are that we camp in a lot of places without water or hookups and cannot easily move during our stay (We go to a lot of events where we are blocked in for the weekend) so it is sometimes nice to let some of the grey out and add more clean water. This is not as big of a deal as with our regular RV with smaller tanks.

I also like to clean out my hose with the grey after dumping, this makes the hose much more pleasant to handle. The tank in the bus has a hose connection to run in water and clean out the tank but I have been finding more places that do not have water available at the dump station. I do have caps for my hose but the grey really cleans it out nicely.

Finally the layout in my bus has a lot of wasted space in the bathroom, and since we were gutting the bathroom I decided to move the shower from across the hall into the bathroom and gain another storage closet. By doing that I had to move the toilet over another 6" from the tank. It was only about 6" away to begin with, but I figured while I was doing all of this I would add in the black tank and get a straight down drop to avoid the possibility of clogs.

kyle4501 · September 18, 2017, 05:52:48 PM

You could put a smaller (~10 gallon) stainless steel tank under the toilet with heat shielding & insulation to minimize heating the contents. You can then add a macerator pump to transfer the contents to another tank that is removable if necessary . . . .

Having the toilet directly over the tank reduces the amount of water needed per flush - which extends your time away from the dumping station.

Zephod · September 19, 2017, 08:58:33 AM

One of the things I've thought about is a 10 gallon tank under the floor of my bus -specifically for black water. I could cut an old fridge up and weld a square box with a bolt-on end with a DIY silicone gasket. Simply paint the inside thoroughly with anti-rust primer and then topcoat. If it rusts through, ah well. And a bit of duct tape will stop the leak until I get to a place where I can build another or am flush enough to pay for a better version.

As for draining etc, I don't really see much problem with not using a macerator but instead using enzymes. They work pretty well on all but unflushable towelettes.

Then you could always have a portable black tank that can just be unhooked and lowered, to cart to the dump site by hand. Wheels on it, of course. No need for nasty hoses!

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