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Other uses for Black Tank with composting toilet


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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

John and Anita

Future (11/20) Oliver Elite II Owners, Hull TBD

Tow Vehicle:  2006 Silverado 2500HD Crew Cab.  6.6L Duramax

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Posted (edited)

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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Snowball • 256 • 2018 Ford Raptor

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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.

John and Anita

Future (11/20) Oliver Elite II Owners, Hull TBD

Tow Vehicle:  2006 Silverado 2500HD Crew Cab.  6.6L Duramax

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Posted (edited)

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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Snowball • 256 • 2018 Ford Raptor

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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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John and Anita

Future (11/20) Oliver Elite II Owners, Hull TBD

Tow Vehicle:  2006 Silverado 2500HD Crew Cab.  6.6L Duramax

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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!

John and Anita

Future (11/20) Oliver Elite II Owners, Hull TBD

Tow Vehicle:  2006 Silverado 2500HD Crew Cab.  6.6L Duramax

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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.

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

'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'

> In line for 2021 OTT EII , TAB Teardrop is up for sale after about 10,000 miles of pleasant learning <

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