Why not use grey water tank for black water?

Discussion in 'Plumbing Systems (The Fresh, The Blue, The Grey, &' started by hrhchuck235, Apr 6, 2017.

  1. hrhchuck235

    hrhchuck235 Member

    Mar 26, 2014
    We have a Jayco Baja. It came with a Thetford cassette which works great. However, my husband, who is in charge of the Thetford, is wondering why the hooch wasn't plumbed with a black water tank? It has a grey water tank which takes in the shower water only. (We rarely shower in the Baja and so it is empty 95% of the time.)

    So, portal experts....is there some reason why the black water couldn't be diverted to the grey water tank which, ostensibly, would hold more than our little cassette?
  2. Haybale

    Haybale I'd rather be camping!!

    Aug 22, 2013
    San Diego via MN
    I would say it mostly depends on the valves and what not to drain it.
  3. hrhchuck235

    hrhchuck235 Member

    Mar 26, 2014
    Thank you Haybale - will check the valves and their capacity, etc.
  4. BelchFire

    BelchFire I speak fluent vise-grip

    Mar 29, 2012
    SE Georgia
    The simple answer is that someone at Jayco decided that it was either cheaper or simpler (or both) to go with a cassette rather than add a flush toilet and a second tank up under the floor. They can buy the cassette ready to install (no plumbing on their part). Additionally, a cassette toilet uses less water because it's not trying to drain through a pipe over any distance; it sits directly above the tank. For your Baja, I imagine that water conservation was probably a top priority in the design process.

    As for the diversion, there's a big difference between gray water and black water. You can dump gray water in a designated area in some campgrounds, but black water MUST go in the sewer. Now, if you were to divert the Thetford into the gray water tank, it has become a black water tank and must be treated as such, and labeled as such, so that no one (you, someone camping with you, or a future owner) inadvertently drains black water into a gray water disposal site. Is the gray water drain large enough to handle the solids that would be present? Is your gray water tank set up to allow it to be flushed?

    I'm not aware of any way that Thetford allowed for a conversion to be done and I doubt very seriously that it would be easy. You might be able to remove the cassette and use the space for a macerator pump, but connecting that to the existing potty would be a real job. I have visions of a custom hack up under the bowl that might leak. For that matter, would you get fumes from the tank up through the shower drain? You know, I've never looked; is there a P-trap in the shower drain to prevent that?

    If you can't finagle a way to convert the Thetford, you may consider replacing it entirely (shower and all) and if you do that -- well, if I were personally considering this, I would have to know more about the specifics of the existing plumbing before I could decide if it was worth the effort and expense of pulling a (gloriously simple and effective) cassette toilet and replacing it with a flush toilet.
  5. Snow

    Snow Well-Known Member

    Jul 19, 2007
    Everything above, plus the fact grey tanks are designed to back up into the shower pans if the tanks become full and the sensors (as they usually do) stop working.. Black tanks usually sit right below the toilet, so it is a straight drop or slight angled drop from toilet bowl into tank..
  6. hrhchuck235

    hrhchuck235 Member

    Mar 26, 2014
    Thank you all for your insight. Right now, we're thinking about the Thetford in a whole new light - it's staying and we're "flushing" the idea of using the gray water tank for anything but shower water. The Portal saves another marriage!
    BelchFire and Orchid like this.
  7. SteveP

    SteveP Active Member

    May 21, 2015
    There is no p-trap between the shower and the grey tank. The grey tank vents to the curb side of the camper, under the awning. Unless you like the smell of black water these would have to be addressed and a new vent installed that goes through the roof.

    I don't see any advantage of a 5 gallon black tank over a 5 gallon cassette. Quite the opposite.
  8. Fleetwood Max

    Fleetwood Max Member

    Aug 14, 2005
    St Louis. Mo
    Very smart move...,
  9. 94-D2

    94-D2 Happy Campin'

    May 21, 2010
    Sutter Creek CA
    I didn't see this posted but In Addition to all stated regarding p traps, vents etc, the gray tank is supposed to be used to flush the hose after dumping the black. I suppose you could flush with clean water but what if you don't have any and then there is the sewer fitting itself. You would have to Rinse that out and I don't see a way of doing it with the hose connected if you have no gray to do it with.

    The cassette is quite easy. Remove from the cassette holder, hand carry to a receptacle and dump. I had one on my niagara and it is useful when set up at a campsite without a sewer. easy. Both systems have their advantages and disadvantages. I didn't like having to rinse out the cassette. But I also don't like having to empty the black tank into a tote and rinsing that either.

    Stick with what you got with the trailer. Changing over is not as simple as it seems.
  10. blondedriver

    blondedriver Member

    Sep 2, 2008
    you can get s
    You can get a spare cassette if you are having a issue of filling to fast
  11. jonshonda

    jonshonda Member

    Aug 22, 2016
    Your husband was not alone in thinking about bypassing the cassette and converting the grey tank. I thought about it too, but came to the same conclusion about all the things missing and issues. I am just really curious how much people use the shower in their pup, vs filling the advantage of a black water tank.

    One of the main reasons we got our Jayco 12hw was the toilet, and my wife and 5/3yo use it either late at night or in the mornings, or the "PAPA I GOTTA GO POTTY" and waited wayyyyy too long to tell you issue. I like the idea of getting a spare cassette though, maybe make a tray under the camper to hold the spare when not in use.

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