Bleeding greywater into black tank

[Ted S.]

Has anyone ever come up with a mod to feed greywater into the black tank - we tend to fill grey faster than black and end up dumping due to full grey but with not so full black. It would be helpful to make use of that capacity.

[trvler]

I bought a twist-on blade valve for $20. It goes on the sewer outlet, and with the twist-on valve closed, you can open the black and grey valves, then the two tanks will mix in the main outlet. I've only used it once, and probably not to full capacity, since I'm still trying to figure out the relative heights of the two tanks (ie if the black tank is higher than the grey, then this will just further fill the grey with the contents of the black).

Before anyone gets excited about the prospect of mixing grey and black - it's no problem for me since we only pee in the trailer.

Anyone know if the two holding tanks are on the same level?

It's a pain that AS makes the classic with a 54 gal fresh tank, and only 39 gal grey. I use very little in the black tank.

[overlander63]

Doesn't the bunkhouse model have a macerater? I suppose you could, for example, place a small basin in the sink, either kitchen or bathroom, put washwater in it, then dump in the toilet.

[Ted S.]

Originally Posted by overlander63

Doesn't the bunkhouse model have a macerater? I suppose you could, for example, place a small basin in the sink, either kitchen or bathroom, put washwater in it, then dump in the toilet.

Yes the bunkhouse has a macernator

We also do wash dishes in a basin and dump in the toilet.

The issue is that the showers fill the grey and so I'd like to get some that grey already in the tank over to the black tank.

I would probably not go the other way contaminating the grey tank with black water, my assumption is the grey tank and associated plumbing is not suitable for black water.

[Protagonist]

Originally Posted by Ted S.

we tend to fill grey faster than black and end up dumping due to full grey but with not so full black.

Isn't that what a Thetford "blue boy" is for? And with a macerator pump, you don't need a giormous blue boy that's the same size as your gray tank, a smaller and easier-to-handle model will do just fine, because you can shut off the macerator pump with the gray tank only partially emptied in order to avoid overfilling the smaller blue boy. It's also a lot easier to take a blue boy to the dump station than it is to take the whole trailer there.

[Ted S.]

I have that tote, Thetford is grey, the blue ones are by Barker Mfg. I actually built a system with 2 totes on a cargo carrier mounted on a front hitch of my truck. I use a Macerator to pump from the tanks up into the totes and go to the dump station. But that is a lot of equipment for a 2-3 day weekend. If I had another 20 gallons of grey capacity I could leave all that behind. That's a big deal if you put together a long trip with a fequent stops. I kind of try to be a minimalist these days from former years of bringing way too much "stuff." It seems silly to me there hasn't been more thought put into maximizing tank efficiency by the manufacturer.

[cwf]

Well, Ted... perhaps using paper plates might reduce 'gray water' usage. Also, some modifications in showering in the AS.. commonly referred to as 'Navy Shower'.. but basically wet, soap, rinse... Or, use the local 'showers'.... Another option would be to set up an 'outdoor' shower for the 'big rinse off', then the shower in the AS would be minimal.

We have found that using paper plates when we have no 'sewer connection' at the site really increases our capability.

With that said, I personally would NOT 'mix' the gray/black tank contents. Here is one reason... Imagine, your 'gray' is really full. You then 'move' your AS... and if you 'brake', the contents can slosh toward the bow... then filling up your shower pan with 'cross-mixed' contents... not the best I would think... If your shower pan is behind the gray tank, accelerating or if not level, the contents will seek 'level'...

I would not ask my lovely bride to clean up that mess... and, if it sloshes outside on to the floor, that might be bad.

Good luck figuring out what works for you..

[HiJoeSilver]

Is this when boondocking? Can't you just drain the gray to the ground? Guess not if you're in a camp w/o hookups.

[Ted S.]

Just to be clear, I would never allow black water in the grey tank, only excess grey into the black tank.

This is when dumping greywater on the ground is not permitted.

However, thank you all for your input.

[Jim Foster]

Drain a few gallons from the gray tank into a bucket and dump it into the toilet. That's one way.
If you do a lot of dry camping, you can put a tube down into the gray tank keeping the end well above the bottom of the tank. Connect that tube to the inlet of a second fresh water pump. There should be a valve behind the toilet which allows you to shut off the water to the toilet. Install a "T" fitting between that valve and the toilet. Connect the output from the second pump to that "T". Turn the water supply to the toilet off. Turn the second water pump on. When you flush, the flush water will be drawn from the gray tank to do the job. You can leave the pump turned on if you wish. It will turn on and off when you flush.
You will be saving fresh water and transferring gray water to the black tank.


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[ianrjam]

My 78 Trade Wind has separate dump valves for black and grey. I thought they all had that.


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[Protagonist]

Originally Posted by ianrjam

My 78 Trade Wind has separate dump valves for black and grey. I thought they all had that.

They do. But the dump lines still come together where you attach the slinky, and so it is possible to mix the black and gray water by opening both valves at once with the cap on in place of the slinky.

The problems with that are many. First, water doesn't just flow one direction unless one tank is higher than the other— it flows both ways— so you not only get gray water into the black tank, but you get black water into the gray tank. The reason is because black water and gray water have different densities due to the chemical composition— urine and feces are both heavier than plain or soapy water and will settle if not constantly agitated. As gray water flows into the black tank, black water flows out under it, until you have a uniform layer of gray water on top of a uniform layer of black water in both tanks.

Second, you can't get the mixed water back out of the dump lines because they're the low point in the whole system, so even after you close the valves again, as soon as you go to the dump station and take the cap off to connect the slinky, sploosh! A mixture of (mostly) black and (some) gray water all over.

Not to mention that driving to the dump station with the dump lines full of water runs the risk of rupturing those lines because they're not designed to bounce around full of water while in transit. Those lines aren't load-bearing.

Which is why if the OP wants to use his black tank to stretch his graywater capacity, it needs to be done by flushing the toilet with gray water and not by cross-connecting the two tanks by opening both dump valves at once.

[Al and Missy]

This is an interesting discussion. Just after buying our trailer about a year and a half ago I read a thread which advocated using gray water to help flush the black tank. As suggested in that thread, when emptying tanks I drain the black tank first, then close the dump valve and open the gray tank valve. After I hear the initial rush of water I close the gray valve and open the dump valve. The inital effluent looks like gray water, indicating to me that the water in the common pipe, and hopefully all the plumbing is, in fact, gray water. After a while (10-15 seconds) I begin to see black tank contents exit the drain. I will do this several times and then as a last step, empty the gray tank which always looks like gray water.

I don't know about the plumbing arrangements, but the bottoms of the tanks are at the same level, as are the pipes from the tanks leading into the dump valve. I would think that the inrush of gray water would push any black tank contents away from the drain outlet as long as the flow was in that direction.

I have not noticed any odor from the shower or sink drains in the trailer. Also, other than concerns about dumping gray water on the ground (which I have never done and probably wouldn't do) how would mixing the contents be any different from the older trailers that do not have gray tanks?

Al

[Foiled Again]

A simple thing is being made MUCH too complex. Get a plastic milk jug (1 gallon size), cut the top off, but leave the handle intact. Shower with the plug IN the shower drain. Bail the shower into the toilet using said milk jug. Flush. Repeat. When the water in the shower is so low it's hard to fill the milk jug, pull the plug.
If the black tank reaches the 3/4 full it's time for a trip to the dump station.

[Protagonist]

Originally Posted by Al and Missy

Also, other than concerns about dumping gray water on the ground (which I have never done and probably wouldn't do) how would mixing the contents be any different from the older trailers that do not have gray tanks?

It wouldn't. But many of the older trailers that have a black tank and no gray tank also have a direct discharge for gray water that bypasses the black tank, because in those days dumping gray water onto the ground was accepted practice everywhere and no one needed a gray tank. But those were also the days of phosphate soaps, and soapy water made excellent fertilizer.

The point is that once you cross-connect the black and gray tanks, you must consider them both as black tanks, and that pretty much puts an end to any chance of dumping gray water onto the ground even where it's allowed, at least until after you thoroughly flush the gray tank to get rid of any potential contamination. If you would never dump gray water on the ground even where allowed, then I guess it doesn't make a difference. But that's a matter of your personal choice, and I can only address the technical explanations. What you do with the information is entirely up to you. I'm not the sewer police.

There is no "inrush" of gray water into the black tank, unless the level of the water in the gray tank is much higher than the level of water in the black tank. If both tanks are only a few inches thick from top to bottom and both mounted below the floor of your trailer, you don't have enough hydraulic gradient (difference in water elevations over distance) to cause any kind of surge; the water surfaces are only a few inches different in elevation at most and a few feet apart in distance by the path the water has to take.

You won't notice any odor from the drains even if the contents of the two tanks are thoroughly mixed. That's why you have P-traps. The water in the P-trap blocks any malodorous vapors from escaping.

[dznf0g]

Although I don't use this practice to get more "trickle" transfer for gray capacity, I do, at the dump station:

1) drain the black tank
2) raise the hose end up high above both tank top levels
3) open the gray valve while black valve is still open
4) listen for inrush of gray into black tank
5) listen for inrush to subside
6) close gray valve
7) lower hose quickly to septic opening
8) repeat.

There is a lot more inrush into the black tank than one would think when the gray tank is at least 1/2 full and the black is empty. I have found this method of black tank flushing FAR more effective than either the AS black flusher or the clear elbow attachment flusher. If one is careful, it is no more risky for a spill than dangling the hose and using the septic water supply hose to clean it up....in fact less so, in my own experience.

[Skater]

We bought a dishpan that we use when doing the dishes to dump the dishwater into the black tank - it helps in a few ways, not the least of which is saving some capacity in the gray tank. Credit to someone on here for the idea.

Also, some newer trailers have the bathroom sink drain into the black tank, rather than the gray tank. If I ever have to work on that section of plumbing in ours, if it's not too difficult I might switch it. However, I know some people say that the black tank then becomes the tank that fills more quickly...

Which leads to the ultimate solution: Use less water. You probably need a lot less water than you think. Use less shampoo. Don't rinse dishes more than absolutely necessary. Turn off the faucet while you're brushing your teeth. Take a navy shower. If you use liquid hand soap, the bottles they come in usually give you WAY more soap than you actually need - learn to press it only partway (less soap - less rinsing).

[dznf0g]

Originally Posted by Skater

We bought a dishpan that we use when doing the dishes to dump the dishwater into the black tank - it helps in a few ways, not the least of which is saving some capacity in the gray tank. Credit to someone on here for the idea.

Also, some newer trailers have the bathroom sink drain into the black tank, rather than the gray tank. If I ever have to work on that section of plumbing in ours, if it's not too difficult I might switch it. However, I know some people say that the black tank then becomes the tank that fills more quickly...

Which leads to the ultimate solution: Use less water. You probably need a lot less water than you think. Use less shampoo. Don't rinse dishes more than absolutely necessary. Turn off the faucet while you're brushing your teeth. Take a navy shower. If you use liquid hand soap, the bottles they come in usually give you WAY more soap than you actually need - learn to press it only partway (less soap - less rinsing).

This, and Paula's solution are the best advice to even things out while dry camping or boondocking, IMO and practice.

[AnnArborBob]

I never liked the various "systems" people claim to use to "equalize" the water in the black and grey tanks in an effort to lengthen the time between dumps. These approaches always seem overly complicated and/or prone to failure.

We put a tub in the sink when we wash dishes and dump the dish water in the toilet, further we practice the "navy shower" approach. With this and with two people, our grey tank lasts over a week. At which time, if we are still in a place with no hook-ups and are not permitted to dump the grey water on the ground, I will bring the trailer to the dump station. Since we aren't going "down the road," the amount of preparation needed to do this is minimal and I can have the trailer back in it's site inside of half an hour. That "half hour" to dump the trailer once per week is a whole lot easier than dragging a "blue boy" with us everywhere we go for occasional usage or the "tank equalization" approach.

[Protagonist]

Originally Posted by Skater

We bought a dishpan that we use when doing the dishes to dump the dishwater into the black tank - it helps in a few ways, not the least of which is saving some capacity in the gray tank. Credit to someone on here for the idea.

I use one of these in my galley sink:
Amazon.com: Advanced Elements 10-Liter Portable Foldup Pocket Sink with Carry Bag

It fits neatly in my Dometic oval sink and by looping the handle over the faucet I make sure it doesn't collapse at an inconvenient moment. Got the idea from the "Small Space Living" thread.