Merging gray and black tanks

[MattE]

Hi. First post so please re-direct me if this belongs elsewhere. I searched but didn't see a pertinent thread.

 

We have a Legacy Elite II, and opted for the Nature's Head composting toilet  That means we are not using the black tank, so want to re-purpose it as an auxiliary gray tank. Has anyone added a slide valve (like a Valterra blade valve) at the outlet in the bumper, then pulled both gray and black valves to let the water equalize between the two tanks?  If so, are there any gotchas or tips that you would like to relay?

 

We'll be very careful not to overfill the black tank, but if it did overfill, would the first exit point be the roof vent? In other words, did OTT completely seal off the pipe where the standard toilet would normally connect to the black tank? They covered it so that I can't see what's under there easily. Or, is there somewhere else water would escape that I'm not thinking of?

 

Many thanks

 

Matt

[Going]

Hi Matt. Great question. I have same situation. Don’t know the answer but would like too. Hopefully you will get an answer.

[John E Davies]

Matt, what you are suggesting has been discussed, but using the black tank for gray storage will just not work without some sort of positive displacement electrical transfer pump. The bottom of the black tank is several inches higher than the rest of the system, so the water will just sit in the drain pipe. You could drastically lower the tongue, but then the grey tank could not drain since its outlet is at the very rear....

 

Using the black tank to gravity feed extra FRESH water to the main tank will work, but I do not think anybody has actually done this yet. It is on my honey-do list, near the very bottom....

 

Use the black rinse port to fill the tank through the existing nozzles.

 

Disconnect the big waste vent and block it off under the bathroom sink, and add a new overflow/ vent hose in the top of the tank, exiting out the floor. Access is easy under the Natures Head.

 

Disconnect and cap the big waste discharge line forward of the slide valve.

 

Add a custom 3 inch slip to 1/2” FPT adapter to the tank outlet,.

 

install a 1/2” line and manual ball valve.

 

Route the line to the right rear and tee the line to the tank fill system near the water heater.

 

Voila.

 

If you can figure out a simple and effective way to store gray water there, please let us know since I actually would rather have that capability.

 

Finally, welcome to the forum. Your input is valued.

 

John Davies

 

Spokane WA

[John E Davies]

Search is 99% useless here, I cannot find the old thread discussing repurposing the black tank. If you haven’t seen this one, check it out.

 

http://olivertraveltrailers.com/topic/natures-head-composting-toilet-installation-in-an-oliver-big-thread/

 

aaaaaaand:

 

http://olivertraveltrailers.com/topic/natures-head-venting/

 

John Davies

 

Spokane WA

[MattE]

Very helpful ,John, thank you. I had seen - and read the majority of - the first thread, but hadn't run across the second. Having read the second one now, I have a question about Jason's response to you. He said ...

 

It is tied into the plumbing line under the bath vanity that vents out the roof of the camper. This plumbing pipe is used to allow air to vent out of the system for proper draining. It is not tied into the black tank, but the black tank flush port is on the outside of the camper. No one can run water into the black tank from outside because under the dinette seat inside the camper we have an inline shark bite valve that you will leave closed to prevent this from happening. The vent is also connected so if they did fill up the black tank it would overflow into the vent pipe and drain into the grey tank.

 

Is he saying that the inline shark valve is between the outside flush port and the black tank? Or between the black tank and the outlet in the bumper? I can't see a shark bite valve under the dinette, but I don't quite know what I'm looking for. If he meant the the former (which I think he meant), it doesn't affect my plan to re-purpose the black tank as an auxiliary gray tank. However, if the latter, it seems it would prevent me from allowing gray water to flow "backwards" into the black tank.

 

Having said that, it may be a moot point though, because it appears to me that the black tank sits higher than the gray tank. In that case, water from the gray will never equalize itself UP into the black tank.

 

Anyone have comments?

 

 

 

Thanks

 

Matt

[ScubaRx]

I think this is doable, not necessarily easy though.

 

During our build of hull # 050 back in late 2013, we discussed using an auxiliary pump to utilize gray water to flush the commode. That idea was a abandoned due to RVIA requirements. My idea was to conserve fresh water for our boondocking adventures and I may yet revisit it.

 

In over ten years of owning two different Oliver’s we’ve never found a need to have greater grey water capacity.  We NEVER put any food particles down the kitchen sink as all dishes (that are not disposable) are washed in a tub. Therefore our grey water consists of nothing but water and a little biodegradable soap from the shower or lavatory.

 

When we are boondocking, the gray water is used to water the local plants. On the rare occasion that we are actually in a campground, it goes out at the dump station with the black water.

[MattE]

John -

 

Somehow I missed this, your initial, response. Yes, I had come to realize that the black tank is higher than the gray. So, my "equalizing" plan definitely will not work with some tricks like you mentioned.

 

I'll keep noodling it, and see if any brainstorms emerge. For now, though, I'm going to move on to something simpler.

 

Thanks again

 

Matt

[Newshoes]

John:

 

 

 

What about filling the black tank (unused with the composting toilet) from the flush port, use a GPM flow meter when filling (about 17 gallons)so you don't overfill the tank. Since the black tank has been unused you now have 17 gallons of potable water in that tank. Not sure how most use the grey tank but I put nothing but water and some dishwasher soap in that tank, no shaving/ toothpaste, food crumbs etc down the drains. So when you drain the grey tank you essentially have clean (some soapy) water. Once the grey tank drains then open the black tank and drain perhaps 3-4 gallons to flush leaving you with maybe 13-14 gallons in the black tank. Could that then be drained and diverted to a bucket for Boondock pumping back to the fresh water system. Seems like boondocking could get an additional 13-14  gallons since I am sure the drinking water would not be the fresh water tank. Since I am new to boondocking when you are in the right place your grey tank waters the plants thru a garden hose discharge connection? Your thoughts?

[SeaDawg]

Newshoes, you're (I think,) in the eastern US, where grey water discharge to the forest or anywhere but a dump station is typically discouraged, or prohibited, and/ or subject to big fines.

Out in the arid part of the west, rules are sometimes different.

Sherry

 

[Overland]

That does not sound like a wise plan.

[John E Davies]

[postquote quote=181317][/postquote]

You can’t keep a dump valve in the circuit when putting fresh drinking water in the black tank, it has to be totally isolated from the grey so contamination of your drinking supply cannot occur by leakage or operator error. Valves leak, owners have brain farts and pull the wrong handle, it must be built totally failsafe.

 

To use your black tank, you must modify the vent system and completely remove the connection to the sewer outlet.

 

John Davies

 

Spokane WA

[SeaDawg]

Yes. I totally misread your post, newshoes. The only viable use for the unused black tank is for extra grey storage, as it is still technically linked to the grey tank. I

suppose you could replumb the bathroom sink to drain to the unused black. A lot of rvs send bathroom sink water to the black tank.

 

Sherry

[Newshoes]

If the issue is sanitizing the combined "Black" / Grey Outfall waste line I have some thoughts on that. I hate to call it "Black tank" as it currently can not and has never been used for that purpose; prefer to call it an Auxiliary tank. Need to consult with my son (The engineer on a nuclear sub) before I resign myself to being uninformed! Thanks to all for the responses. I hope my ideas have merit as it could expand boondocking "days on station" by 3-4 days!

 

 

[Raspy]

I haven't looked to see how practical it would be, but maybe we could re-plumb the sink drains to go to the black tank, and then add a valve at the dump fitting in the rear bumper area, then leave the grey and black dump valves open.   The gray water would flow to the black tank and on to the gray tank.  When the gray tank was full, you'd shut off the gray dump valve and continue using water until the black was full.  It would not matter that it was higher than the gray.  Then dump them both by dumping the black first and then the gray.  Then start the process over.

 

This wouldn't give us any more fresh, but it would increase the gray significantly.

 

The problem might be that there would not be any slope in the drain lines leading to the black tank.  This might cause solids to settle and possibly build up in the smaller 2" lines.  Also, the shower would not drain to the black tank, because the shower floor is so low.  This would mean we'd have to manages the shower gate valve and only shower when the gray was not full.

[John E Davies]

[postquote quote=181362][/postquote]

I call it the Black Tank because it is black ABS (the others are translucent PVC), not because it has ever had any fecal nastiness inside it..

 

You also need to think about a future owner and the ability to easily put it back to a factory configuration.

 

John Davies

 

Spokane WA

 

 

[Overland]

[postquote quote=181362][/postquote]

As I said, this is not a wise plan. The valves on the grey and black tanks DO NOT IN THE SLIGHTEST provide a sanitary separation between the two, and your grey water is not nearly as sanitary as you think. So before you set sail on the Typhoid Ollie, you need to completely separate that tank from the grey, both the drain and vent.  Unless, that is, you plan to carry a good supply of Cipro and camp only in ER parking lots.