Bathroom Sink Water: Does it go to grey or black tank?

[chaseav]

I've heard that in "some models" the bathroom sink waste water discharges into the black tank instead of the grey one in order to ensure there is a better solid / liquid ratio in the black tank. Any truth to that?

Specifically interested if the 2015 25FB Intl Signature does.

[CruizinDux]

Originally Posted by chaseav

I've heard that in "some models" the bathroom sink waste water discharges into the black tank instead of the grey one in order to ensure there is a better solid / liquid ratio in the black tank. Any truth to that?

Specifically interested if the 2015 25FB Intl Signature does.

I had heard that the above was the case for the 20's. I called JC and they emailed me a plumbing detail and it didn't appear to be true.

After flushing the BW/GW tanks I turned off the supply to the toilet, turned on the vanity faucet, and listened when I opened the flush valve. There may be a delay depending on your layout. Mine was not connected, tho I can see the convenience and intent of that connection.

Bob

[CRH]

Why not just run the sink faucet and open a valve when the tanks are empty to see for yourself?

[overlander63]

Originally Posted by chaseav

I've heard that in "some models" the bathroom sink waste water discharges into the black tank instead of the grey one in order to ensure there is a better solid / liquid ratio in the black tank. Any truth to that?

Specifically interested if the 2015 25FB Intl Signature does.

Nope.
Airstream did that a few years ago, but seem to have stopped after owner complaints about the practice. Now instead of simply dumping the bathroom sink water into the black tank directly below it, there is a pipe running some distance just to put it in the grey tank.

[OTRA15]

Ditto to Bob CruizinDux, our FC20 head sink goes to the grey tank.

[Wayne&Sam]

My 2014 25' rear twin does.

Just turn off the pump and/or city water, dump a pitcher of water down the sink, hold the flush valve open on the toilet and look and listen.

I think it's a good feature. Our grey tank fills up, but the black never does. So putting the sink into the black tank helps the grey tank last longer.

[Sphere Guy]

That's incorrect overlander63.

My 2016 28FC has the bath sink dump into the black tank. It is said they do this because of mouth waste entering the grey tank, is better to go into the black. Rather, it is because it is closer to the black tank and easier to plumb in.

I don't have an issue with the bath sink waste going into the black tank. It increases the liquid volume for dumping.

[Chuck]

I'm doing a full reno, and when I re-assemble, I could just as easily plumb the lav sink into the grey or black tank. The replacement black tank is big (22gallons).

What is your vote? (anyone)

I'm thinking that there isn't much volume coming from the lav sink, so it wouldn't likely negatively impact the black tank;
There can never be enough grey storage, so every little bit helps.

[CruizinDux]

Originally Posted by Chuck

I'm doing a full reno, and when I re-assemble, I could just as easily plumb the lav sink into the grey or black tank. The replacement black tank is big (22gallons).

What is your vote? (anyone)

I'm thinking that there isn't much volume coming from the lav sink, so it wouldn't likely negatively impact the black tank;
There can never be enough grey storage, so every little bit helps.

Vote: I would have preferred the BW connection for the above reason. I'm staying pat as I have other/higher priorities.

Bob

[OTRA15]

Chuck, I would prefer the black tank for this use, but how about plumbing a waste line to each (B/G) so that future owners can have the choice? Or maybe a "Y" valve which would permit an active ongoing choice? This way, if the grey tank is getting full, one can always switch to the black tank, and also be able to pour galley sink grey water (captured in a Rubbermaid clean-up tub for instance) down the head sink.

Future owners might balk at having the head sink permanently plumbed to the black water tank IMO.

BTW, do you have the option during your reno. to increase the grey tank size? That would be cool but space is probably limited.

Good Luck!

Peter

[Chuck]

I was actually thinking that same thing, about having a choice...but I can't picture how you would plumb that with 1 1/2" drain line.
Grey tanks have definitely been enlarged. Went from 0 (no factory grey) to 36gallons.

[HowieE]

What in Gods name is going on here? What difference does it make where the waste water goes. Do you think the dump station has a little man hiding down there that directs things based on what tank you just drained.

The solution I have used on several trailer to extend the volume of the gray tank was to couple close to the top of the gray tank into the lower side of the black tank. That way when the gray tank fill it automatically drains to the black tank.

[$hide]

Umm, just make sure if yours is drained into the black tank that you never let the bathroom sink drip in cold weather. Voice of experience speaking here. It is a mess. That was 20 years ago. With every trailer since then that is the first thing I check since we are often in below freezing weather.

[HowieE]

Originally Posted by $hide

Umm, just make sure if yours is drained into the black tank that you never let the bathroom sink drip in cold weather. Voice of experience speaking here. It is a mess. That was 20 years ago. With every trailer since then that is the first thing I check since we are often in below freezing weather.

The only time it would be advisable to offset freezing weather with a dripping faucet would be if you had and were using a sewer connection.
Generally during anticipated freezing one should disconnect from a city connection and let the city hose cock drip. That protects the city side so it is available in the morning. Use the fresh water tank water while disconnected.

[Minno]

We originally plumbed our bathroom sink into the grey tank, but found we were having issues with not enough liquids in the black tank. Before we completely closed up the bathroom plumbing, we replumbed the sink into the blank tank, and haven't had those issues since.

Kay

[OTRA15]

Originally Posted by Chuck

I was actually thinking that same thing, about having a choice...but I can't picture how you would plumb that with 1 1/2" drain line.
Grey tanks have definitely been enlarged. Went from 0 (no factory grey) to 36gallons.

You could stub up from each tank, and put an inline ball valve in each riser, then Y -- or aligned T's -- to the single sink drain. Always keep one ball valve closed. Granted you would have to operate each valve regularly, so it did not freeze up from the gunk just above it.

Great move to go for 36 gallons of grey. Our FC20 only has about 20 grey and it is limiting. We just ordered a rolling grey water tote for the next trip.

What is the size of your new black water tank?

Peter

[OTRA15]

Originally Posted by HowieE

What in Gods name is going on here? What difference does it make where the waste water goes. Do you think the dump station has a little man hiding down there that directs things based on what tank you just drained.
. . .

Easy . . . easy . . .



Actually it makes a big difference, as grey water can be disposed of legally in many spots (like the flowers-only garden behind our garage), and in many rural campgrounds if permitted.

For those who boondock, or who are otherwise not hooked up to a sewer connection, maximizing the amount of waste water that can be handled without dumping is of paramount importance. We aim to have both holding tanks full when we dump.

If putting the bath sink waste water into the black tank stretches out the need to dump for one more day, that is a big difference worth having IMO.

[Chuck]

Black tank is 22gallons. Replaces the original 13 gallon tank...which was good enough for a typical weekend (but just barely). So I'm thinking that 22 will seem "huge" to us, now.
there's 3 of us...one of whom is much larger than he was the last time we camped, and continues to grow...so that matters, too.

[Sisu]

We have a 2013 International 30; our bathroom sink drains into the black water tank. This occasionally becomes an issue when we have no sewer hookup and stay in same site for 2 weeks. We deal with the gray water by using a portable tank; I prefer not to use the portable tank for black water.

[Zybane]

The owners manual on 2015+ Classics show a diagram of the bathroom sink emptying straight down into the black tank.