Connection grey to black tank

[vtraudt]

As in our Class C, our habbits/use of grey and black water capacity always creates the problem that the grey tank is FULL quickly, and the black is almost empty.

Over the years I always thought but never further looked into the possibility of an 'overflow' where the grey tank can overflow into the black tank to make use of this wasted capacity.

I assumbe both tanks (Forest River travel trailer) are rectangular and fairly close together.

I also assume that all grey water 'feeders' (shower, toilet sink, kitchen sink) have traps (smell), so no additional trap is needed between the 2 tanks?

Aside from plumbing issues (adding to connections to the top of both tanks, finding space, etc), any other things to consider?

[2112]

Oh, and when you have the new waste valve closed, you open the gray dump valve, wait a few seconds and then open the black dump valve, and your wife says it smells like the cat took a dump under the bathroom sink, it's time for a new air admittance valve. Mine failed while transferring gray tank contents to the black tank. I carry a spare air valve now. When you have to buy one, you might as well buy two.

[2112]

vtraudt wrote:
That (tub in sink) is one way, certainly. Just trying to come with one more along the 'work smarter, not harder'.
Its desease (engineer), can't help it.

The idea is to get a strong, hard flush of water straight down into the black tank to bust up what may have stuck to the bottom. Would you rather stick your arm or a broom handle down there to bust it up?

I understand your disease very well. Retired EE, master tinkerer here.

[vtraudt]

That (tub in sink) is one way, certainly. Just trying to come with one more along the 'work smarter, not harder'.
Its desease (engineer), can't help it.

[shum02]

2112 wrote:


We also use a plastic tub in the sink when washing dishes and pour that soapy water into the toilet. In my mind it helps prevent the dreaded pyramid and keeps the black tank clean. Does it actually work? I have no idea.

We do the exact same thing and I do believe it works great. I've never had issue with the black tank and the dreaded pyramid of poo.

[ktmrfs]

vtraudt wrote:
Yes, I now see what you say: the grey and black MERGE ("T") already at the drain hose.

Just modify to make a "Y" with 3 valves (grey, black, main drain) or 2 (main/black (3.25 I think in my case) and grey (much smaller, maybe 2").

Normal operation: all closed.

Move grey to black: keep main/drain closed, open grey. If grey level is higher, will push into (fill) black.

Empty: open all.

exactly. And in our trailer we have a 36 gallon grey tank for the bathroom and a 36 gallon grey water for the galley. do the same thing if one grey gets full to equalize between the two grey tanks.

BTW when dumping, this also makes a quick and easy way to backflush the black tank. Empty the black, close main outlet, open grey and let it backfill into the empty black, close it, then drain the black again. repeat as appropriate.

[jdc1]

A Valtera Flush King 45 Degree Reverse Flush Valve Attachment would be what you want to use....like Valhalla 360 says. Close the adapter. Open grey. Open black. Close grey and black when they level out. Now your 40 gallon grey is 60+- gallons

[2112]

I do it as Valhalla360 outlined. I usually wait until I hear my shower burping before I open the gray.

We also use a plastic tub in the sink when washing dishes and pour that soapy water into the toilet. In my mind it helps prevent the dreaded pyramid and keeps the black tank clean. Does it actually work? I have no idea.

[vtraudt]

Yes, I now see what you say: the grey and black MERGE ("T") already at the drain hose.

Just modify to make a "Y" with 3 valves (grey, black, main drain) or 2 (main/black (3.25 I think in my case) and grey (much smaller, maybe 2").

Normal operation: all closed.

Move grey to black: keep main/drain closed, open grey. If grey level is higher, will push into (fill) black.

Empty: open all.

[valhalla360]

JRscooby wrote:
As for connecting the tanks. Once you do that you have no grey water, it is all black, unless the black can't back into the other tank. And that connecter will be a good place for blockage, hard to clean, and real stink to grow.

Who cares if it's legally black water?

Gray water often smells worse, so no real stink concern.

Assuming everything drains to a single point, a simple and cheap solution is to buy a temporary twist on valve.

https://www.amazon.com/Valterra-T58-Twist-On-Waste-Valve/dp/B000BGHYJS/ref=asc_df_B000BGHYJS?tag=bingshoppinga-20&linkCode=df0&hvadid=80401840125241&hvnetw=o&hvqmt=e&hvbmt=be&hvdev=c&hvlocint=&hvlocphy=&hvtargid=pla-4584001431142158&psc=1

Attach the temporary drain valve and leave closed.
- After the gray gets full, open the gray valve.
- Then open the black valve
- (again keeping the temporary valve closed)
- The greater amount of water in the gray tank will flow down and then back up into the black tank.
- When you do get around to dumping, close all the valves, attach the hose to the temporary valve, then open the black followed by the temporary valve...once empty open the gray valve.

[JRscooby]

1 of the Mods Dad had me do to his 5th wheel was put a drain point at about the 3/4 level of the grey tank. Had 2 valves; Open 1, would drain into stinky slinky, the other thru a hose bib to fill a container, into the sewer with a small hose, or where allowed, to water bushes.
FHU site, drain top of grey until black full, still plenty to chase the black. When he had to haul all water, do dishes in pan, and dump in toilet. (Can flush with dirty water)

As for connecting the tanks. Once you do that you have no grey water, it is all black, unless the black can't back into the other tank. And that connecter will be a good place for blockage, hard to clean, and real stink to grow.