Motorhome - 2000 Safari SerengetiThe black tank in our MH on our last couple of trip has overfilled twice only 2 days into our trip. After the second time we could hear water going into the black tank while using the sink in the bathroom. I know, impossible.We completely drained and washed out the black tank to do some of our own troubleshooting. Gray tank registered at 60% which is usually pretty close to actual. We turned off all the water to our MH and used a garden hose and placed water into the bathroom sink and could hear water enter the black tank and water did drain when the black tank dump valve was pulled. This will happen if we use the kitchen sink or the shower, I know all one tank but did it to confirm that.In the past if the gray over filled it would come out in the shower, lowest point in our MH. But it is not over filling.Help, we have no clue to what could be happening. Anyone out there have any idea what could be happening

We have friends with a mid 90s Serengeti. The bathroom sink is plumbed into the black tank. What about a washer...do you have one, and does it go in the black tank?

Many RVs, including mine, have the bathroom sink drain into the black tank. The reasoning is to be sure you have plenty of water in the black tank to prevent buildup of solids. I prefer it that way. Are you using too much water from the bathroom sink?

Our Monaco is the same way. Bathroom sink drains in to the black tank. Kitchen sink and shower in to the grey tank.

With my clipper (40 years old), the kitchen sink and shower drain to the gray tank; the bathroom sink and toilet drain to the black tank. Much more common than you think.

Consider it a feature, not a bug, and plan accordingly. As zigzagrv noted, this helps ensure that the black tank is adequately hydrated, although overflowing after 2 days may suggest you'll need to cut back on using the bathroom sink, or just dump more frequently.

Black Tank Fillin to Fast | Good Sam Community

13 Replies

DSDP_Don
Explorer
Jul 13, 2015
Even though you have a plumbing diagram, keep in mind that many of those diagrams are for several lengths of coach. Often, plumbing the bath sink into the black tank is a matter of convenience/fit, where it may be too hard to reach the grey tank or a cost savings issue.
jplante4
Explorer II
Jul 13, 2015
Your Serengeti should have a black tank flush (hose connection right next to the water fill on the water panel).
Fishbreath
Explorer II
Jul 13, 2015
If you have gotten much more usage out of it on prior trips, I would suspect that you now have an accumulation of solids in the tank, hence reducing the capacity.

I agree with the above post. You should place some ice in it and drive around (taking corners!) to break up any solids.

After draining, I would then use a 5 gallon bucket to fill it up to check capacity.

Good luck.
Bill
Passin_Thru
Explorer
Jul 13, 2015
Drain it and run the Bathroom sink. You can put 20 lb of ice int he tanks after you drain it a d ride around a bit then redrain and see if it breaks up some solids in the tank. Stranger things have happened.
Old-Biscuit
Explorer III
Jul 12, 2015
dwurnitsch wrote:
Thank you all for you input.

The local RV shop said that it would be impossible for the bathroom sink to drain into the black. Thank you for confirming it does. But looking at the diagram of the system the bath sink does shows draining to the Grey Tank. Reading the holding tank alittle closer does confirm bath sink does drain into black. Diagram is wrong.

So maybe the hose water test into the kitchen sink to see if it went into the black tank actually didn't. We will need to retest during our next trip.

Washer we don't use but it drains directly to the main tank drain and not into a holding tank.

Again thank you for your comments.

Aren't you glad you came HERE and got the correct information vs relying on that local RV SHop??

I would think twice before having them do any repairs.

Bathroom sinks draining into black tank is not only common but has been done for many years
Vulcan_Rider
Explorer
Jul 12, 2015
Also.....how many female members are there in your "camping group"?

Maybe somebody needs to be coached about using less water per flush.

Nobody leaves the water running in the sink while brushing their teeth......right ??
CarlGeo
Explorer
Jul 12, 2015
dwurnitsch wrote:
Thank you all for you input.

The local RV shop said that it would be impossible for the bathroom sink to drain into the black. Thank you for confirming it does. But looking at the diagram of the system the bath sink does shows draining to the Grey Tank. Reading the holding tank alittle closer does confirm bath sink does drain into black. Diagram is wrong.

So maybe the hose water test into the kitchen sink to see if it went into the black tank actually didn't. We will need to retest during our next trip.

Washer we don't use but it drains directly to the main tank drain and not into a holding tank.

I have a 1997 Safari Serengeti, and my bathroom sink does drain into the black tank. I believe this is the case for all Safari coaches of similar vintage.

Again thank you for your comments.
dwurnitsch
Explorer
Jul 12, 2015
Thank you all for you input.

The local RV shop said that it would be impossible for the bathroom sink to drain into the black. Thank you for confirming it does. But looking at the diagram of the system the bath sink does shows draining to the Grey Tank. Reading the holding tank alittle closer does confirm bath sink does drain into black. Diagram is wrong.

So maybe the hose water test into the kitchen sink to see if it went into the black tank actually didn't. We will need to retest during our next trip.

Washer we don't use but it drains directly to the main tank drain and not into a holding tank.

Again thank you for your comments.
NoVa_RT
Explorer
Jul 12, 2015
Consider it a feature, not a bug, and plan accordingly. As zigzagrv noted, this helps ensure that the black tank is adequately hydrated, although overflowing after 2 days may suggest you'll need to cut back on using the bathroom sink, or just dump more frequently.
toedtoes
Explorer III
Jul 12, 2015
With my clipper (40 years old), the kitchen sink and shower drain to the gray tank; the bathroom sink and toilet drain to the black tank. Much more common than you think.