Holding Tanks

Topic: Holding Tanks (Read 622 times) previous topic - next topic

Holding Tanks

May 02, 2016, 10:23:27 am

What flows into the "Black" waste tank beside the toilet ? Bath Sink, Shower, Kitchen sink? I have a 1994 U300 Unihome, build number 4466. Do not know of any pluming diagrams for these units.

Re: Holding Tanks

Reply #1 – May 02, 2016, 10:30:51 am

Our '93 U280 has the "Drop & Plop" toilet - the stool is directly above the black tank - straight shot down to the reservoir.

Nothing else (to the best of my knowledge) goes into the black tank.

Re: Holding Tanks

Reply #2 – May 02, 2016, 10:32:13 am

My thoughts too Chuck.
JohnH

Re: Holding Tanks

Reply #3 – May 02, 2016, 10:32:42 am

Only the toilet drains to the black tank. All other drains flow to the gray tank.

You could test to verify. Dump the tanks and leave the dump hose connected. Close the dump valve for the black tank and leave the gray valve open. Run water to each drain in the coach and see which flow to the dump hose.

Re: Holding Tanks

Reply #4 – May 02, 2016, 11:01:51 am

I had an SOB where the bathroom sink drained into the black tank. Probably a good idea.

Re: Holding Tanks

Reply #5 – May 02, 2016, 11:05:51 am

Quote from: Tom Lang – May 02, 2016, 11:01:51 am

Probably a good idea.

Why?

Re: Holding Tanks

Reply #6 – May 02, 2016, 11:21:47 am

Quote from: Chuck & Jeannie – May 02, 2016, 11:05:51 am

Why?

First, coach layout suggests what drains into what tank on most RV's.

Yes, toilet always into black. But with certain layouts the run from, say a sink, would be straighter if run into the black tank.

As to why that would be good:
IF, repeat IF gray and black are the same size, gray generally fills up 3-4 times faster than black. Better balance means longer between need to dump.

Adding more water to the black tank never hurts in terms of keeping everything liquefied.

Again, the vast majority of all coaches toilet to black, all else to gray.

Re: Holding Tanks

Reply #7 – May 02, 2016, 11:37:24 am

Quote from: wolfe10 – May 02, 2016, 11:21:47 am

IF, repeat IF gray and black are the same size, gray generally fills up 3-4 times faster than black. Better balance means longer between need to dump.
Adding more water to the black tank never hurts in terms of keeping everything liquefied.

Brett,

Those of us with third valves use it to rinse the black tank from the gray tank after dumping the black tank.

Without dumping, if the gray tank started getting too full, could you (keep the third valve closed throughout this procedure):

Open the gray valve,

After a short while, then Open the black valve.

Since water seeks its own level, I would expect the gray water to flow into the black tank. After closing both valves, then you have more room in the gray tank.

The only downside I see is you would have some gray water between the tanks and the third valve.

Or am I being too simplistic?

Trent

Re: Holding Tanks

Reply #8 – May 02, 2016, 12:03:39 pm

Trent,

Yes, a third valve works great when both tanks are at the same "elevation".

Have seen a guy with SOB try that only to find out that the gray tank was ABOVE the black. Didn't work out quite like he had hoped!

Re: Holding Tanks

Reply #9 – May 02, 2016, 12:31:28 pm

My holding tank level indicators have a resolution of 1/4 tank. Unless you're absolutely sure that the grey level is above the black - in the tank and in elevation, and also, water will flow back and forth after the initial flow, umm, I think I would not advise...

Re: Holding Tanks

Reply #10 – May 02, 2016, 01:00:05 pm

It's all non-potable, contaminated water. I don't think cross contamination either way makes any difference.

Rich

Re: Holding Tanks

Reply #11 – May 02, 2016, 01:08:32 pm

When equalizing tanks I put my ungloved hand on the plumbing and the instant I feel the flow rate drop I close the black valve.

Not as accurate with the valves behind a wall but might still work some?

Re: Holding Tanks

Reply #12 – May 02, 2016, 01:24:56 pm

And many coaches come with single tank for Black and Gray

Re: Holding Tanks

Reply #13 – May 02, 2016, 01:37:44 pm

Quote from: Tim Fiedler – May 02, 2016, 01:24:56 pm

And many coaches come with single tank for Black and Gray

I have had separate black/grey, currently have the single and love it.

Re: Holding Tanks

Reply #14 – May 02, 2016, 03:44:50 pm

Quote from: Rich Bowman – May 02, 2016, 01:00:05 pm

It's all non-potable, contaminated water. I don't think cross contamination either way makes any difference.

I'm with Rich. No need to fret about black tank capacity. If you have done the "3rd valve mod" to your coach, you can operate 2 tanks just like a single tank: leave the 3rd valve closed, and the two dump valves open. As long as the top of the tanks are level (or "on the same elevation" as Brett said), you don't have to worry about a "overflowing" situation until both tanks are full. This is unlikely to occur when dry camping in a Foretravel, because the total capacity of the two waste tanks usually exceeds the capacity of the fresh water tank by about 50%.