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Other uses for Black Tank with composting toilet


NCeagle
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Hi all, I've been reading and learning all about the fresh, gray and black water tanks.  Fresh water and/or filling up the gray tank seem to be the main drivers of having to pack up and leave your dry site (assuming the gray tank cannot be emptied on-site).  Our Ollie will have the composting toilet option since we plan on boondocking often.  I confirmed with Oliver sales that the black tank is still installed and just not used, so I'm thinking that it would be great to take advantage of that to increase the capacity of both the black and gray tanks.

Has anyone with the composting toilet ever done anything innovative with the spare tank?

Based on the assumption we will always have filtered and/or bottled water with us and will never drink or cook with the water from our fresh tank, would this be feasible:

- Pre-campsite, fill both the clean fresh and black water tanks with fresh water.  So 32.5 + 18.5 = 51 gallons of fresh water to start with.

- when 18.5+ gallons have been used from the fresh water tank, transfer / pump the fresh water in the black tank into the fresh water tank (essentially, refill it back to 32.5 gallons). 

- transfer / pump 18.5 gallons from the gray tank into the now empty black tank to make room for the new water in the fresh tank.

- leave campsite when there is no more water in the fresh tank and the gray and black tanks are both full of "gray" water

- Empty tanks in a legal place, rinse, wash/bleach and repeat. 

I'm looking into various water storage solutions and before I buy anything I'd like to see if this is a possibility.  Any thoughts on this appreciated!

Thanks!

John

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It's been discussed several times before, but to my knowledge, no one has followed through with anything.  I removed my black tank and use the space for storage, if that counts.  

I'm certain that something is possible, but only with a lot of work and lowered expectations.  And I think that combination, combined with plentiful, inexpensive, and much simpler solutions for storing extra water elsewhere, is why no one ever follows up.  

Specifically to what you're thinking - I certainly wouldn't want to use the black tank for both fresh and grey water - I don't think you can sanitize it nearly as thoroughly as you'd need.  

I do think that you could fairly simply transfer fresh water from the black tank to the fresh, but you'd have to remove the drain connection between the black and grey tanks to prevent contamination, and then remove the check valve on the cleanout port so that you could use to it both fill and empty the tank.  Perhaps replace it with a manual valve.  And you'd have to add an overflow of some sort.  But if you did all that, then you could just simply run hose from there to the boondocking port and pump the water in.  

But, I think that's a lot of trouble when compared to a couple of $15 plastic jugs in the bed of your truck.  

Edited by Overland
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1 hour ago, Overland said:

It's been discussed several times before, but to my knowledge, no one has followed through with anything.  I removed my black tank and use the space for storage, if that counts.  

I'm certain that something is possible, but only with a lot of work and lowered expectations.  And I think that combination, combined with plentiful, inexpensive, and much simpler solutions for storing extra water elsewhere, is why no one ever follows up.  

Specifically to what you're thinking - I certainly wouldn't want to use the black tank for both fresh and grey water - I don't think you can sanitize it nearly as thoroughly as you'd need.  

I do think that you could fairly simply transfer fresh water from the black tank to the fresh, but you'd have to remove the drain connection between the black and grey tanks to prevent contamination, and then remove the check valve on the cleanout port so that you could use to it both fill and empty the tank.  Perhaps replace it with a manual valve.  And you'd have to add an overflow of some sort.  But if you did all that, then you could just simply run hose from there to the boondocking port and pump the water in.  

But, I think that's a lot of trouble when compared to a couple of $15 plastic jugs in the bed of your truck.  

Yep - definitely good points and sounds like far more trouble than it's worth.  Taking the tank out and using the space for storage definitely counts!  The reason I started thinking about this was storage space in the first place - trying to conserve some space in the back of the truck if possible.

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I agree with Overland. 

The only likely "simple" (and maybe not so simple) use I could see for the unused black tank would be for extra grey, by  plumbing the vanity sink to the black (which is often actually done in many rvs and boats.)

Most of us don't use that sink much, so it might not even be worth the effort. Even if you routinely dumped dishwater into that sink from a dish pan, it's not that much water, though it would help. The shower is the big grey water generator. 

Sherry

 

Edited by SeaDawg

2008 Ram 1500 4 × 4

2008 Oliver Elite, Hull #12
 

 

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2 hours ago, NCeagle said:

Yep - definitely good points and sounds like far more trouble than it's worth.  Taking the tank out and using the space for storage definitely counts!  The reason I started thinking about this was storage space in the first place - trying to conserve some space in the back of the truck if possible.

You’ll find that even taking the tank out for storage space gives limited benefit and isn’t all that easy. I had to chop mine into pieces to get it out, which was fun but also not fun. You could of course take out the toilet floor and remove the tank in one piece but that’s even more trouble. 

Then there’s the question of what to do with that space. It’s narrow and not easily accessed so you need to put some thought into what you’d actually store there before you go through the trouble. I cut out a hatch in the floor just smaller than the footprint of the toilet, added a tray underneath and that’s where I store extra bags of peat for the toilet. That actually works quite well since of course you have to remove the toilet to empty it, so there’s your extra peat.  I also gained a bit more space under the dinette seat and that’s where I carry spares, my repair kit, and an electric heater. 

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Wow.  Now I know why it's been discussed but no one has tried anything like I was thinking.  I don't think I'll be removing the tank either if I can't take it out whole and replace it if we ever decide to sell or switch toilets.  I'll just rest easy for now knowing that I have a spare tank on board that won't need any special attention.  Thanks Overland and SeaDawg for sharing your thoughts and experience.  I'll just have to make do with various water storage containers to make it all work if/when we'll be camping dry for an extended period. 

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I still want to do this, to turn it into an “Aux Fresh Water” tank, it would not be especially hard to do and the tank is higher than the main fresh tank, so it would gravity drain, through a 1/2” PEX line and ball valve, when that one is empty. It is not very high on my Honey Do List tho....
 

If you do this, it will mean a future owner will not be able to bolt down a conventional toilet. For me, that reason would not be important enough to stop me from cutting pipes....😀 Some folks with SUVs cannot simply throw three jerry cans or a bladder in the truck bed. A converted black tank would be an excellent solution for those owners.

When you have converted yours, please post pics and a shopping list of parts. Being a pioneer/ Beta engineer is hard.

John Davies

Spokane WA

 

"Mouse":  2017 Legacy Elite II NARV (Not An RV) Two Beds, Hull Number 218, See my HOW TO threads: https://olivertraveltrailers.com/topic/john-e-davies-how-to-threads-and-tech-articles-links/

Tow Vehicle: 2013 Land Cruiser 200, 33" LT tires, airbags.

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I'm going to look closer at this once we have our Ollie in November - it's tough right now for me to envision and understand what is involved without getting my head down in the plumbing.  One of the first things I'll be working on will be trying to improve the insulation and/or heat around all the plumbing.  I know winter camping is more challenging but I'm an avid skier and with Covid ruining ski season last year and threatening again this season (hotel availability mainly), I'm thinking a winter camping trip to a ski resort parking lot may be in the cards sooner rather than later.  Some ski resorts offer dry camping in their parking lots for free or a very nominal fee.  One of the (many) challenges with this "winter" use case is using a bladder may not be possible due to the freezing potential.  With a converted black tank and proper insulation and heating, that shouldn't be as much of a concern.  Fun to think about!

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>> How to utilize the existing black water tank (deposit liquids) from the bath/shower space in the case where a composting toilet is fitted ?

(0) I am assuming that depositing partially treated urine or other liquids into the black tank could be a benefit in some situations. 

***************

I have the thought that a flat box (rectangular hollow and slightly bigger than the footprint of the composting toilet) can be constructed that :: 

(1) will increase the height of the composting toilet ( ? 1.5 to 3 inches ?) and I acknowledge the extra height is a challenge.

(2) has an opening at the bottom that fits into the black tank floor toilet hole.

(3) has access port or ports outside the footprint of the composting toilet such that a tube/funnel will permit pouring in liquids.

(4) built to come apart so that the interior can be cleaned as needed.

(5) Gas/drain Trap: possibly ?? the interior construction could allow a sort of drain trap to keep gasses/smells from easily exiting any time the input port/tube/funnel is used. This feature seems a bit of a stretch when trying to keep the unit thin so as to not raise the composting toilet too too high.

(6) the top surface of the box would fit/accommodate the bottom of the composting toilet so all items may be secured. the fitting of the box into the toilet tank drain would in itself prevent any siding/shifting.

***************

Boondocking :: Thoughts on efficient use of water. 

Having spent some time 'long long ago in a land far away' living on very small boats, I found it possible to live a clean and comfortable life while using very little water for washing everything. The trick was to use "Low Flow/High Pressure" ( pump up garden sprayer in my case ). We as a society assume water is an infinite free resource and easy disposal is a given, hence we commonly use Low Pressure/High Flow which doesn't work out too well when boon-docking etc.

If a luxury warm shower for two is a gallon or less and if rinsing off dishes after washing is measured in ounces, it is conceivable that one can easily boondock for extended times even if one has to transport potable water in and grey and black water out of the campsite.

***************

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'There is so much good in the worst of us, and so much bad in the best of us,it doesn't behoove any of us to speak evil of the rest of us'

> 2021 OTT EII , TAB Teardrop has good home after 10,000 miles of pleasant learning <

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  • 4 months later...

With a composting toilet installed, I would like to use the BLACK water tank as another GRAY water tank to expand the time I have before I have to dump either. Would it be that difficult to plumb a connection between the BLACK and GRAY, so that the GRAY would overflow to the BLACK?

I'm assuming that the "vanity sinK" is currently connected to the GRAY tank.

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DeeKay, As I mentioned a couple of posts above, the black tank is several inches higher than the grey. So you would need a pump to do what you suggest. Also it would be difficult to keep an inlet screen free from debris like hair and soap scum. Draining in the reverse direction, black to grey or black to fresh, would be simple.

And yes, the bathroom sink drains into the grey tank, along with the shower. They share a common drain line, which is where the isolation (“travel”) valve comes into play, it blocks that pipe so smelly water does not slosh up into the shower pan when you hit the brakes.

PS, I think in another post you mentioned you were getting an Elite, you need to clarify when asking questions, since there are differences in the way the systems are laid out. If you don’t specify, most people will assume the larger trailer since that is by far the most common model.

John Davies

Spokane WAl

Edited by John E Davies
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"Mouse":  2017 Legacy Elite II NARV (Not An RV) Two Beds, Hull Number 218, See my HOW TO threads: https://olivertraveltrailers.com/topic/john-e-davies-how-to-threads-and-tech-articles-links/

Tow Vehicle: 2013 Land Cruiser 200, 33" LT tires, airbags.

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I am still in my Casita but wanted to say that I use my sink very little. I don't cook inside so clean up is done outside. I enjoy long hot showers and stay in campgrounds....I enjoy the walk to the showers...find them clean...I still wear shower shoes. And this may be TMI, but I never use the the camper  toliet for anything but #1 and dispose of paper in a small lined container/trash can that I empty daily. Dumping is a breeze and I have zero issues. I really like having the camping adventure which reminds me of my younger days of tent camping...except now my sleeping is dry, warm/cool, not on the hard ground/... comfortable...lol. I'm sure I will try boondocking someday but until now this is how I travel....

 

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  • 2 months later...

Still thinking about unused Black Tank: ( EII #751 w/ composting )

Motivated by dreams of extended stays at places with few or no facilities.

URINE STORAGE ::: People generate LOTS of urine but 18 gallons of urine storage would last a while . . 

BLACK KITCHEN WATER STORAGE :::  We are trying to control the quality of the water in grey tank to make it less noxious/intrusive/nasty so as to facilitate disposal into the environment when necessary/possible.  The water in kitchen is going into small dishpan in sink where fats/oils are broken down with soap and solids/particulates settle out before liquids go down the drain .  BLACK TANK is a great place for the stuff that is messy, chunky and stinky and with care 18 gallons of storage could last for a while . .

************************************************

ACCESS to BLACK TANK:

OLD Original idea was: ( complicated flat drain box under composter that used regular toilet drain flange-pipe assemble )

(a) lift compost toilet 

(b) Install std toilet hardware (flange w/pipe and sealing bushing into plastic tank top)

(c) construct somewhat complicated flat hollow base under compost with inlet ports to side of composter that sets on top of std flange and under composter /// weird-wonky and raises an already tall composter . . 

----------

NEW Improved idea from Jason is: ( small pipe into top of black tank set near bathroom wall with some funnel/cap thing at top of pipe )

Talked to Jason at new owner pickup time and asked to purchase the parts used to plumb the std toilet so as I could proceed with OLD ORIGINAL IDEA and his suggestion was (a) a new hole in fiberglass floor (b) enter black tank top with same type rubber-ish sealing bushing but do this off to the side ?somewhere? and thereby avoid the rather complicated construction and future cleaning/sealing issues of the OLD Original Idea shown above. 

So , (i) identify the pipe-in-hole sealing bushing type/name/mfg like that which Oliver uses in std toilet install and then check available sizes, (ii) measure/find black tank under floor to evaluate possible placement of new pipe (iii) figure out details of pipe size/location/top fittings-funnel-cap-?trap or notrap?-mounting/bracing/prettyness . . . stuff. (iv) start using the black tank.

-----------

Any thoughts appreciated.

 

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'There is so much good in the worst of us, and so much bad in the best of us,it doesn't behoove any of us to speak evil of the rest of us'

> 2021 OTT EII , TAB Teardrop has good home after 10,000 miles of pleasant learning <

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It’s great to see all these ideas.  For us, the black tank is our limiting factor when dry camping.  The composting toilet wasn’t available when we ordered, I guess I could swap out.  I just wish Oliver would use a larger capacity black tank.

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I think that using the black tank as you suggest would work, but personally I would be horrified to have the big ugly pipe just sticking up out of the floor. How about instead, using the vent pipe as a fill tube? Install a hinged waterproof access hatch under the vanity as others have done, tee into the vent and bring a new pipe out to where it can be accessed. If you could figure out a rubber gasketed coupling that would allow it to pivot, that would be more excellent.  I would not like to dump cooking waste where it might spill and run down inside the hull 😬

I also wonder how you will clean all the new parts, the black tank was never intended to store greasy stuff, just more natural, errr, organic deposits. A regular flush of nearly boiling water when you are connected to a sewer might work.

Or do what we do, just wipe the pots and pans with a paper towel and put it in the trash bag - no solids and very little grease goes down the sink.

John Davies

Spokane WA

Edited by John E Davies

"Mouse":  2017 Legacy Elite II NARV (Not An RV) Two Beds, Hull Number 218, See my HOW TO threads: https://olivertraveltrailers.com/topic/john-e-davies-how-to-threads-and-tech-articles-links/

Tow Vehicle: 2013 Land Cruiser 200, 33" LT tires, airbags.

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3 hours ago, georgelewisray said:

URINE STORAGE ::: People generate LOTS of urine but 18 gallons of urine storage would last a while . . 

BLACK KITCHEN WATER STORAGE :::  We are trying to control the quality of the water in grey tank to make it less noxious/intrusive/nasty so as to facilitate disposal into the environment when necessary/possible.  The water in kitchen is going into small dishpan in sink where fats/oils are broken down with soap and solids/particulates settle out before liquids go down the drain .  BLACK TANK is a great place for the stuff that is messy, chunky and stinky and with care 18 gallons of storage could last for a while . .

I'd think a better option for pee would be to just buy an extra bottle.  But we've never found disposal to be difficult.

With the kitchen water, aren't you just trading one yucky tank for another?  Or realistically, adding a second one?  Personally, I think the fewer things to keep clean the better.

I still think the best use of the black tank is to cut it out for storage space.  No regrets here.  

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