Our Forest River Work & Play is configured so that the kitchen sink drains into the black tank. I'm not fond of this configuration because it fills up the black tank faster--the one tank you don't want filling up quickly when you're dry camping. Is this common? In my mind it certainly makes more sense to have it drain into the grey tank.

I can't tell you what it's common, but my kitchen has it's own gray tank which is great. Have you looked to see if adding a tank is possible? It not only adds capacity but when I have full hookups I leave that one open and never have to worry about it.

Some makers feel that the black tank needs more water to be effective. This is their way of creating that assuming that most owners don't use enough water when they flush.

I would think, in a two tank system, that would be ideal. Many people complain of running out of gray tank space and pouring water into the toilet to save what space they have. This lessens the problem and also helps alleviate the 'black tank pyramid.'I have a three tank system and would love to have my kitchen sink running to my black tank and using both gray tanks for the shower/bathroom sink. I could go even longer when boondocking. After five days, my shower gray is almost full but my black and kitchen gray are about 1/3 full each.

Technically kitchen sink water is black water due to the food particles. But it is really unusual for it to be plumbed into the black water tank. The kitchen sink usually goes to the gray water tank or a separate galley tank.When in ultra conservative mode we wash dishes in tubs and poor the water into the toilet to save space in the gray. We fill the gray tank probably three times to filling the black tank once in normal use.

My bathroom sink runs into the black tank. It was probably done because it was easier than running it to the grey tank. This seems to be fairly common.In any case, I like it because the grey tank always fills faster than the black. In previous RVs we used to dump dishwater into the black tank.This is the first I have heard of the kitchen sink being plumbed into the black tank.

Kitchen Sink Drains to Black Tank | Good Sam Community

25 Replies

DaButcher
Explorer
Sep 06, 2013
This is what I'm doing
dougrainer
Nomad
Sep 06, 2013
hershey wrote:
I have said before that I would like to have my sink drain into my black tank, but:
I would have some reservations about the possibility of the smell baking up thru the sink drain??? I know there is a trap but travel motion can cause that trap to fail. Could that be a problem or am I nit-pickin'?

You worry too much:B IF the travel motion "could" cause the P trap to empty (it does NOT), then there would be thousands of motorhomes/trailers with horrible smells in them. One thing I CANNOT get my customers to understand is this---GRAY tanks smell 10 times worse than Black tanks. Almost ALL tank odor problems in an RV come from a Gray tank issue, NOT the Black Tank. Most RV'ers use Black tank Chemicals. THAT breaks down the Black content and also masks any odors. Don't use a chemical and everytime you flush you get that "outhouse" type odor coming back up. IF you do NOT smell anything bad at your toilet when you open the flush valve, then the odds are, if you have a tank odor in your RV, it is coming from the Gray tank. YES, if any P trap or mechanical vent in the RV fails, then you will get a horrible gray odor inside the RV in transit. Doug
64thunderbolt
Explorer II
Sep 06, 2013
They are mfg for ease of assembly. Not to be practical or convenient for us. If it holds together till the warranty is up they are happy.
Lantley
Nomad
Sep 06, 2013
John&Joey wrote:
Some makers feel that the black tank needs more water to be effective. This is their way of creating that assuming that most owners don't use enough water when they flush.

I agree my kitchen has its own Gray tank. It's a pain because it seldom has more than 10 gallons of water in it, if that. My 40 gallon black could easily accommodate 10 more gallons.

I understand the tanks have to be strategically placed within the infrastructure of the RV. However I don't think enough real life input is considered in the engineering/layout/design process
hershey
Explorer
Sep 06, 2013
I have said before that I would like to have my sink drain into my black tank, but:
I would have some reservations about the possibility of the smell baking up thru the sink drain??? I know there is a trap but travel motion can cause that trap to fail. Could that be a problem or am I nit-pickin'?
Bobbo
Explorer III
Sep 06, 2013
beemerphile1 wrote:
SteveB wrote:
1st: kitchen water is not black water....

The Free Dictionary
"blackwater (blkwôtr)
Wastewater containing bodily or other biological wastes, as from toilets, dishwashers, or kitchen drains."

Business Dictionary.com
"Black Water
Water polluted with food, animal, or human waste."

And we all know the internet can not be wrong.

My bathroom sink drains into the black tank. I like that feature.
robatthelake
Explorer
Sep 06, 2013
When You get right down to it ,maybe there really only needs to be One Tank ! black!

Obviously the Toilet is Black Water, so should be the Food Scraps in the Kitchen Sink and seriously who hasn't peed in the Shower or Bathtub?

One Tank ...One Dumping Rule ..End of Problems!
Harvard
Explorer
Sep 05, 2013
Our batroom sink is plumbed into the black tank and the additional water helps with keeping the solids floating.
otrfun
Explorer II
Sep 05, 2013
beemerphile1 wrote:
otrfun wrote:
...After two days, our black tank was about 2/3 full, the grey tank about 1/3 full....

If you are basing this on the factory tank monitor - you have no idea how much is in the tanks. Many of us just ignore the monitor due to its inaccuracy.

I've flushed both my grey and black tanks with a Flush King a few times. I use a water flow meter to make sure I don't overfill them. When I compare the water flow meter results with the onboard water level gauge the results are pretty close on my unit. I also have a clear view of the bottom of the black tank through the toilet. Very easy to visually gauge how full it is.

Now the freshwater onboard level gauge on my TT is another story. It reads 1/3 when it's empty :(
dougrainer
Nomad
Sep 05, 2013
1. There is NO CODE that says a gray water cannot be plumbed to the Black Tank. The reason a Gray would be plumbed to the Black tank is because the Floorplan of the RV does not allow that particular sink/shower to be plumbed to the gray tank. So, they run it to the Black tank
2. NEVER leave a holding tank valve open when using the RV. The reason is this--IF you leave it open, the solids do not always flow out the tank (Gray or Black) and then you get a sludge in the tank. ALSO, you do not want that slime/sludge flowing over the Dump Valve Cavity when the knife valve is left open. Those foreign debris will migrate into that cavity and cause the valve to not seal when you then try to close it. Doug