why separate tanks for grey and black water?

[porkslap]

Hi Folks,

Let's say I'm building my own RV. Is there a reason I can't use the same tank for grey and black water?

-Tom

[SuzzeeeQ2012]

porkslap wrote:
Hi Folks,

Let's say I'm building my own RV. Is there a reason I can't use the same tank for grey and black water?

-Tom

imagining the smell coming up from the sink
:E

[Bobbo]

As has been mentioned several times, I use the gray to flush the stinky slinky after dumping the gray, so for me, separate tanks are required.

An absolute NO NO is allowing black tank water to come up in the shower floor because the tank is over full due to incorrect indicator lights. We have the gray tank water come up into the shower floor at least once a year. This absolutely, positively requires separate tanks.

[Katdaddy]

We dry camp and are not particularly good at water management. We have a blue tote and dump our gray tank several times in the course of a week. Couldn't do that with a combined tank.

[dieharder]

If you forget to check your levels and fill the tank, most times it will fill up your bath first. DW will beat you butt raw if she's in there with a mix of grey and black water because there isn't any room for it to drain.

[Naio]

Thanks from me, too, to all who posted. I learned lots from this thread.

[porkslap]

Great thoughts, I appreciate all your insights.

I was thinking about one tank just for space and cost reasons. But I'm starting to think two tanks would probably be easier in the long run.

Thanks again everyone!

-Tom

[Mr_Mark1]

I like the one tank idea as the black tank is alway needing water. Of course it will all depend on the capacity of the tank.

MM.

[K3WE]

Let me repeat something with some emphasis.

You dump the black tank and then run what is PREDOMINATELY SOAPY gray WATER through the drain hose as a rinse-out...

It's a nice feature.

(This and all the other reasons folks have listed make the two tanks a nice way to do things)

[Community Alumni]

We sit in one location for several weeks a time, two tanks allow me to leave the grey open all the time and only flush/rinse the black once a week or so.

[ependydad]

TexasShadow wrote:
none other than practical.
gray water can be dumped, sometime, at some places, on the ground, legally, where black water must always be dumped in a legal sewer receptacle.
so sometimes, you can extend your stay at a campground without moving your rig.

This is interesting that it's been mentioned so many times. I've literally never camped in a campground that allowed this.

BB_TX wrote:
There has been a couple occasions when I forgot to check the grey tank level. Backed up into the shower while I was in there. Found myself standing in an inch or two of water. Glad it was grey and not a mix of black.

This alone would be a reason for 2 tanks. This happens to us quite often that we let a tank backup before I go empty them. Having poo-flavored water in any sink or shower would gross me out.

Randu wrote:
Much easier to store and handle a sewer hose that has been flushed out with gray water than one with black.
Randu

If I use a black tank flush, I don't worry about doing gray last for my sewer hoses. By the time that I am done, it's flushing clear water through which is better than the stinky gray tank any way. But, I only have dumped at my full hookup site where I didn't have to worry about time or a line behind me. If dumping at the campground's dump station is a regular thing, this might not be something that you can bank on as much.

[dave17352]

jplante4 wrote:

dave17352 wrote:
I actually explained what I do wrong. I leave the cap on the sewer outlet and open both the black and grey valve.

I did it this way...once. Then I realized that I had a mixture of black and grey water between the valves and the cap that had no place to go except into the waste bay. Holding the hose above tank level accomplishes the same thing with no mess.

My outlet is outside. I simply close the valves and open the little hose cap and drain what little is in the line into the hose then connect the hose and drain. No problem at all for me. I know some people simply hook a valve right to the end of there dump valve accomplishing the same thing.

[jplante4]

dave17352 wrote:
I actually explained what I do wrong. I leave the cap on the sewer outlet and open both the black and grey valve.

I did it this way...once. Then I realized that I had a mixture of black and grey water between the valves and the cap that had no place to go except into the waste bay. Holding the hose above tank level accomplishes the same thing with no mess.

[Golden_HVAC]

porkslap wrote:
Hi Folks,

Let's say I'm building my own RV. Is there a reason I can't use the same tank for grey and black water?

-Tom

Many times I can camp for a few weeks in one location, and dump my grey tank on the local plants (into a hole about 12" deep that is buried within about 1 hour to prevent flies from discovering the water). Sometimes in a National Park, or other developed campground (where you might have neighbors within 600 feet of you) you can not dump the grey water, and must do things like dump shower water into the black tank to extend your time before going to the dump station.

Also if you ever camped, and had the grey water back up into the shower, you will understand the NEED to not have black water in the grey tank.

Back in the 70's a lot of RV's only had one tank. And they might have backed up into the "Wet bath" when camping, and make a turn or drive down a winding road, and you could splash out a lot of water into the shower pan.

That is why RIVA requires two tanks in most RV's.

My buddy designed his RV and it's storage tanks. His grey water is mounted above the black water tank, and he has the ability to drain his 150 gallon grey tank independent of his 100 gallon black tank, or drain the grey into the black tank, to wash it out better.

So he can drain his black tank, then wash about 50 gallons of grey water into the black tank, and then drain that (removing all the solids) and then rinse again with the remaining grey water. Any time he is dry camping, and grey is say 90% full and black is only 10% full, he can drain some from black to grey and camp another week or so.

I think his fresh water tank is a stainless steel 150 gallon tank. He rarely needs to fill it completely, unless planning 3 weeks of dry camping!

For tanks, try this website. Tank-Depot.com

Good luck with the planning!

Fred.

SunElec.com sells solar panels for about $1 per rated watt. I would suggest a couple of 100 - 150 watt panels, and grow from there if you need a larger system.

[dave17352]

Dutch_12078 wrote:

jplante4 wrote:

dave17352 wrote:
I agree with all the posters here. Now on occasion I have equalized my tanks when I need more grey water room by opening the grey valve and leaving the black tank valve closed. This brings them to the same level.

I don't see how this equalizes the level. If you were to open both valves and hold the stinky slinky above the top of the tanks, then the fullest tank would sluice into the emptiest tank. Hopefully, the grey tank is fullest.:E

I do this to provide a little extra liquid to flush out the black tank. Be sure to hole the hose high.

I added a third "Main" valve to my dump setup. To equalize the tanks, I just leave it closed while opening the grey and black valves. When dumping, I open the black and main valves, and when the black tank is empty, give it a quick rinse by closing the main valve and opening the grey valve for a couple of minutes before opening the main valve again to drain the grey water.

I actually explained what I do wrong. I leave the cap on the sewer outlet and open both the black and grey valve. Both of my tanks are mounted at the same level in my TC holding area. With both valves open the tanks equalize. Like I said if doing this I know I will not have have sewer water in the shower because I know both holding tanks can hold the entire 46 gallon fresh tanks contents. I checked this to make sure before doing this. Works great if needed. But usually this is not necessary but when it is it works great.