Really? Does your RV’s bathroom sink drain into the sewer tank?

40

Most RVers assume the sinks in their RV drain exclusively into a gray holding tank. The toilet, most RVers believe, drains exclusively into the black (sewer) tank. But is that always true? In this eight-minute interview by RVtravel.com editor Chuck Woodbury with RV waste systems authority Doug Swarts of Drainmaster.com, you’ll learn that sometimes the bathroom sink does, in fact, drain into the black tank.

Doug even points out that at least one manufacturer drains the liquids from the sink, shower and toilet into the same tank!

While it may be no big deal to most RVers where the water in their bathroom sink drains, to some it can, indeed, be a big deal when conservation of liquid waste is important — as in boondocking, when every ounce of waste liquid matters.

After you watch the video, please answer our brief poll directly below the video. Do you know where the water in your bathroom sink drains?

Okay, would you now please take our survey. Thanks.

##RVT975


 

Subscribe
Notify of

This site uses Akismet to reduce spam. Learn how your comment data is processed.

40 Comments
Newest
Oldest
Inline Feedbacks
View all comments

John
3 days ago

Easy to find out. With all tanks empty. Open the black water drain. Turn on faucets and shower see if any water comes out black water drain.

Tom Macfarlane
7 days ago

I assume it goes into the gray tank, and I know for sure that the shower water does.

Robert Lea
7 days ago

I was mystified by how fast my black tank filled up while parked for the winter at a FL RV park. I was dumping it about every 4 days. No way were we using the toilet that much. A neighbor suggested that perhaps another fixture, such as the bathroom sink, was draining into the tank. So I performed a simple test.
Emk

Robert Lea
7 days ago
Reply to  Robert Lea

Simple test (continued): drain both black & grey tanks & flush. Run substantial quantity of water down the drain of suspect fixture. Open black tank dump valve. Any water discharged? Open grey water dump valve. Any water discharged? You will easily determine where each fixture drains to. What did I find? The kitchen sink drained into the black tank! That’s why we were filling the black tank so quickly! Now I’m trying to determine if and how I might replumb the drain. Doesn’t look good.

eric
7 days ago

I have a 1955 Spartan Mansion (32 ft) trailer that was originally a park model with no tanks. The toilet sits between the two axles with minimal clearance so the best design I could come up with is a 26 gallon black tank for my toilet, kitchen and bathroom sink connected to a 12v macerator pump (which pumps to another 26gallon auxiliary tank, then to my sewer connection. My shower is on a separate 26 gallon gray tank with a separate sewer connection so in total I have 72 gallons of gray/black storage. I bought the tanks from Elkhart Plastics which was the only tank supplier that had a tank with the dimensions i needed.

It works great but I dread the day the macerator pump breaks. Macerator pumps are used in boats all the time so they do have a good track record.

Linda
7 days ago

The manual says the bathroom sink drains into the black tank. I know this is right because you can smell the fumes coming out of the sink when water is running or when we are driving. Thought I’d put in one of those white things you see advertised that take out the u-joint and says it stops the stink. Turns out there is already one there. I now leave the plug in all the time with a cup of water in the sink. No more stink. Have to be careful brushing teeth not to get a mouthful of stinky air when spitting.

Norm Worthington
8 days ago

We have a 2017 Redwood and while just getting it back from the factory shop (4th time) we wanted to be sure that they fixed ALL the tank level indicators. With empty tanks we first stuck a garden hose into the kitchen sink and filled it until it was backing up in the sink…ok. that one’s full….however the indicator showed 1/3 filled. Then to the shower…same thing, filled till I had water above the drain (indicatorshows 2/3d full)…well, might as well flush the bathroom sink a little to clean the gooseneck…..to my surprise the water level in the shower didn’t come up…? but we checked the black tank and showed enough water in it to light up the black tank indicator. Finished by filling the black tank with the hose. my thought is that the drain for the washer (prep) was going into the shower gray tank instead of the black. The tanks all needed fresh cleaning anyway…found out I can take longer showers now!☆

Cheryl Sheldon
8 days ago

I have a Heartland Edge M18. I haven’t confirmed but suspect the sink drains into the black tank based on how quickly the black fills.

John Koenig
8 days ago

Something related but not mentioned: I’ve seen standard RV “drop” toilets (as opposed to macerating toilets) where there is a SHARP BEND (think ~ 90º) IMMEDIATELY and, the “solid waste” MUST make said sharp bend before it is carried off to the black tank. In stick & brick homes, waste lines MUST be CAREFULLY installed. I believe the the requirement is 1/8″ drop for each 12″ of pipe run. That’s a VERY small margin. More than 1/8″ drop allows liquid to drain faster than it can carry solid waste away. Less then 1/8″ drop allows the solids to collect IN the pipe rather than be carried away. This means that LEVELING the RV would be critical (even more so than an RV refrigerator requires). Fail to achieve this high level of accuracy when leveling an RV virtually guarantees plumbing problems. I saw this type of drop toilet at an RV rally. I have no idea if this installation technique is commonplace. RVers with this plumbing should probably use extra water when flushing solid waste.

Mary Hazel
8 days ago

My 84 Toyota Dolphin front bath has sink and shower draining into black tank-found out hard way. Ugh. After much research on replumbing etc I switched to a C-Head compost toilet and now have 2 grey tanks and no black tank. All working very well!

Ron Hale
8 days ago

We discovered the bathroom sink drains to the black tank shortly after we purchased our Class C motorhome. I found a deep plastic kitchen food storage container that fits perfectly in the sink, which we use for tooth brushing, shaving, etc. Then it is dumped down one side of the kitchen sink, and into the grey tank. Helps keep the black tank from filling so quickly.

John Koenig
8 days ago

A simple way to check where your sink(s) empty into would be to empty ALL holding tanks. Then, empty several gallons of water down the sink you want to test. Open the BLACK tank and check if water is running through the sewer hose. If water IS running through said hose, you know that sink empties into the black water tank. No water emptying through said hose? Then close the the black tank valve and open the grey tank valve. If water IS emptying through the sewer hose, that sink empties into a grey water tank. The easy way to run this test would be at a FHU (Full Hook Up) RV site. The tests shouldn’t take very long and, you’d know for sure which sinks / drains on YOUR RV empty into which tanks. It would also be a good time to give your holding tanks a thorough cleaning.

Robert N. Cordy
8 days ago

Why do we really need to separate gray and black waste? Why not just one “integrated” tank, or more for larger rigs? I could understand the need in the distant past when we drained our gray water onto the ground, but now?

KellyR
8 days ago

Not that long ago I was at a park that upon check in I was told I could dump gray on the ground. No site hook-up but had a dump station. I assumed it was so they did not have to pump the dump station as often.

Ken
8 days ago

Now I need to buy some food coloring and run some tests. I boondock a lot.

John Sciortino
8 days ago

Chuck,
Next spring on my first camping trip, I’m going to fill my bathroom sink & plug it with the stopper. Then I’ll turn off the pump & flush the toilet until the water stops running in the toilet. Then with the toilet valve still open, I’ll empty the sink. I should be able to hear or see the sink water splashing into the empty black tank, if that’s where it goes. Then I’ll do the same thing with the tub.
What do you think?

Scooter
8 days ago

Our puma 295bhss has two grey tanks. Aft tank only is fed by the outside kitchen sink. Forward grey tank is fed by the main kitchen sink, bathroom sink, and the shower. It fills up fast unless crosslinked with the aft tank (giving full 70 gallons of capacity). Got one of those external gate valves to link the two tanks without making a total mess when uncapping the sewer cap.

Drew
8 days ago

Not such a bad thing. For dry campers it leaves a little reserve for the gray- which fills faster anyway.

Ralph Caldwell
8 days ago

Scamp 16 trailer. No bathroom sink. Bathroom shower pumps to grey water tank. Kitchen sink (only sink) gravity drains to grey water tank.

Brian Baker
8 days ago

I’ve had three motorhomes , a Triple E, an Empress and a Miramar. All three bathroom basins have drained into the black tank. It’s very easy to tell which tank the basin drains into. Have your tanks empty, with the tank valves closed and fill your basin. Drain the basin, open your grey tank. If water comes out it is going in the grey tank, if not it is going in the black tank.

David S
8 days ago

The sink in the half bath drains into the black tank. The full bath in the back goes to the gray. 2014 Winnebago Tour. 

BadWolfe
8 days ago

Learned that the bathroom sink drained into the black tank while cross country traveling. We were definitely surprised. Didn’t like the black tank filling up so quickly, so we started thinking of “work arounds”. Didn’t like the thought of washing our hands in the kitchen sink, so, if we are traveling or boondocking, we place bowl in the bathroom sink. Then, when full, dump it in the shower drain. I was even thinking about rerouting the plumbing.. but that is for another day.

John
5 days ago
Reply to  BadWolfe

I dont understand why your worried about washing your hands in the kitchen sink? Our RV bathroom sink has a standard trap under the sink which protects any smells coming up thru the black tank into the sink… just like houses are built. If your RV doesnt have a trap then that is a big problem and makes no sense.

BadWolfe
5 days ago
Reply to  John

You are so correct. I know it doesn’t make actual sense, it’s just the thought of using the facilities, then washing our hands in the same place we wash our vegetables, prepare meals and fill water bottles.