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Black and Gray Tanks and Waste Master Install

Our Wet Bay in our 45LP Allegro Bus

Our Wet Bay in our 45LP Allegro Bus – Before Upgrade

Well, it is now time to talk about a dirty subject…Gray and Black Tanks! “Oh what joy!” Yea, I know! I am super excited about it also. (hummmm….)

Now many people asked about this and this usually means they are new to RVing and just do not really know. We have all been at that point of not knowing how this should be done and seeing we get asked at least three times a month, well, we are over due at making a post and a video that we can point people to. But this also gave me a great chance to put in a new sewer hose system that uses a totally different fitting that does not leak, with a MUCH more industrial hose that would take a lot to hurt it. It’s called the Waste Master. Waste Master was designed and tested for years by Drain Master and then it was sold to LCI as they had a much larger distribution network. (Thus the like names) However the Drain Master company is still involved. (Ok, that was more than you needed to know, but thought I would mention it as you may find it on either site and the names are, well, the same but different.)

So, black and gray tanks. I will make this quick and easy as their really is not much to understanding the use of the tanks. (Ok, after writing the blog post it was not a quick post after all. Who knew their was so much to write on the topic?) Now I KNOW that people WILL HAVE AN OPINION on this. But this is how WE do it and the logic as to why we do it the way we do. And after all, we are the ones being asked. :) But of course, please feel free to comment and help others.

The “Black” tank is used to store your digestive waste. This comes from the thought that the waste is much darker in color. I guess it could have been called the “brown” tank seeing the “Gray” tank is used to store used water such as sinks and showers and as such the way it actually looks is gray when it comes out.  But oh well that is the way it is. (Guessing that maybe early on the tanks themselves were actually black and gray in color and so it stuck. Today they are usually the same color…black.)

RULE: Dump black tank first and then the gray tank right after it so it will flush out the tube. So what this also means is that if you are one to leave the gray tank open all the time…BE SURE to close the gray tank so you can build up liquid in it of at least 30% before you dump the black tank. You NEED to flush out the tube after you dump the black tank. So, when black gets to about 50%, close the gray tank and by the time you are needing to dump the black, you will have enough gray water for the tube flush out.

BLACK TANK – Leave this CLOSED all the time until it is time to empty it. “But Dave, I have full hookups and so I am connected to a sewer.” Well great! But leave it closed! “But why Dave?” Well, your “solid” waste has no way of being able to flow out of the tank without being pulled out by all the liquid waste and flush water that is allowed to build up when you have it closed. So if you leave the tank open, your solid waste would just go “Plunk” down into the tank and would just stay there while the flush water and “#1” would just run out. (That is until the outgoing opening gets plugged from to much solid build up then you are in for some bad times.) So leaving it closed allows for all the flush water and “#1” to build up and up and up. You dump the tank when it gets to be above 70% (Give or take.)  This way you would have built up enough liquids that when you open the tank it would create a “whoosh” and a suction effect that would then pull the solids out with it.

Then if your RV has a tank rinse, you turn that on when the meter gets down to about 20% left and let it run some. This will help to knock things down the walls and also help to push some of the solids towards the opening. After a few minutes I then close the black tank and let the rinse run some to put some liquid into the tank to start it off.  Again, I do not want solids to just go “plunk” into the tank and stick there. Having liquid already in the tank will help with it not sticking so it can be pulled out.

GRAY TANK – Ok, this is the touchy one. I think we can all agree that the black tank stays closed until needed to dump for the reason stated. But the Gray Tank can go either way…open or closed when hooked up to a sewer line. So what is one to do?  Well, like the black tank, the gray tank can also have solids in it from rinsing plates etc.  But what is worse, the grease or oils that can and do go down the drain no matter how you may try not to. They can and will build up on the side walls and even the bottom of the tank making a “mucky paste” of ick!

Icky muck build up from Gary Tank!

Icky muck build up from Gary Tank! (Click to see larger Image if you dare.)

To prove this in the video you will see that I added a clear drain extension and left the gray tank OPEN for a month. You will see that over time an oil and grease sludge built up on the side of the clear tube that the gray tank was on. So what this means is if you leave the tank open all the time, you WILL get a build up in your tank as these will stick to the sides and grow in thickness. If however you leave it closed, then just like the black tank, you will then be able to have a lot of it pulled out when dumped at about 70% (give or take) as most will be floating on top of the water and thus be pulled out.

Now that is not to say that you can not leave the gray tank open, and a lot of people do. But that does mean you should be using something like Happy Campers Holding Tank Treatment to help treat the tank to dissolve it the best you can. We do this when we travel by having at least 50% in the gray tank and adding Happy Campers to it when we travel. As we drive it will slosh around and when we arrive, we will then dump the tank, thus clearing it out the best we can. We do try to wait at least 8 hours (say 4 hours of driving and then another 4 hours. Or better yet, letting it sit overnight after the drive and then dumping in the morning. (Gray tank only…If doing it on the black tank, dump right away as it will all be mixed up thus not having time to skink to the bottom.)

So…Do we leave ours open or closed? Well, that changes for us. If we know we will be doing laundry all day we will open the tank and thus we will not have a quick build up of gray water.  However, for the most part, we keep the gray closed and open as needed. Yes, of course you then tend to need to dump the tank more often then just when the black is full. This is one reason in the future I will be adding electronic dump valves so we can do it right from our bathroom. :)

“So Dave, why now make this post?”  That is because I just got a new hose system that needed to be installed and thought I would do it all at the same time.  Tank talk and tube talk.


RhinoFlex – IMHO

You see, I have grown frustrated with the darn hoses because the one I used to use, the RhinoFlex by Camco, has gotten really bad in manufacturing IMHO. I went through two of them in three months because the hoses would split at the spine. In the past I had used them for years without issue. Then we bought the new coach and I wanted a nice new hose. Well it seems that they changed the plastic or something and I had two bad experiences due to cracks. So then I looked for another solution and I found the gray Viper hose by Valterra that was looking to be great! Well not so fast. While I like it a lot better than the RhinoFlex, I did end up getting a hole in it that I needed to seal with Emergency Tape and I did not like the fact it would not stay in place as the rubbery tube will not stay coiled when used. As such, even if you are 5 feet from the sewer, all of the 20 feet of hose will be out and uncoiled.


Waste Master

I then came across the Waste Master hose system. After being stung to many times, I was fearful of the price as I hated to spend more only to have more expensive issues. Also, it was different. And by that, I mean that it does not use the bayonet locks that are on almost all RV’s, it uses a CAM lock system. Unlike the bayonet locks that seem to be used ONLY in the RV industry for liquid. CAM locks are used across the world as a secure, leak free, easy to use hose linkage system. Ever see a fuel tanker truck hooking up to unload fuel to a gas station tank? If so, you had seen CAM locks in use. They are used industry wide from fire trucks to tankers and even fueling jets. So why is it that the RV industry choose long ago to use a bayonet flitting vs a proven positive locking system for dumping waste? NO CLUE! I can only guess to make after market products that are only used for RV’s, thus being able to make more income.  HOWEVER, they still could have used a system that THE ENTIRE WORLD uses just as easy and still made their own hoses etc.



So…After researching and actually talking to the guy that came up with the CAM lock hose system for RV use, I was willing to modify our coach to use CAM locks and thus allowing me to use an industrial, patented, drainage hose!  (Do you know how hard it is to patent a hose? Lets just say it is as hard as one would think, a hose is a hose is a hose. Nope.)

Cutting off tab with hacksaw blade.

Cutting off tab with hacksaw blade.

But when I say modify the coach it may sound worse than it is. It actually takes under 10 minutes to do and can be done by anyone. (Well, almost.  I asked Brenda to and she said no.) It just involved cutting off the four tabs that the bayonet uses on the bottom of the “Y” pipe and then glueing on the new CAM fitting to the end of the “Y” pipe.  POOF!  New industrial fitting that uses a hose that seems to really be something that would take a lot, and I mean A LOT, to hurt. Also when you have it in place where you want it…It says in place. It will not uncoil like the gray hose did.

I did mentioned the higher price of the system. However what I did not mention is I did spend more in three months on replacement hoses than the system costed me. So, in theory, this should be the last hose system I should ever have to buy.  Also, when we change coaches some day, I will simply buy a new “Y” pipe and replace the one I put the CAM fitting on thus allowing me to take my totally awesome new waste drainage system with me. (Well, as totally awesome as sewer waste goes.)

TIP: If you choose to also go with the Waste Master system, be sure to get the “Back to Bayonet Adaptor” also. Why? Say you are dry camping somewhere and they offer pump out service, then they will likely come with a bayonet fitting to attached to your RV. (Because that is what they would expect you would have of course.)  So you then can pop in the adaptor and have the correct fitting so you can then dump. You can also get a 20 foot extension hose for those times when you just can’t reach.

New CAM Lock Fitting Installed!!!

New CAM Lock Fitting Installed!!!


After using this new system for a short time I will already go on record to say, I truly think that this is the best waste draining system hands down! From the correct type fitting, IMHO, to the totally great industrial hose, right on down to the “business” end having a shut off.

Attn RV Industry: Please be so kind to switch to a proven system that just works and does not leak. And by that I mean going to a CAM lock fitting that is simple to use, does not bind up, and does not leak.




So I made a video.  (Of course) In the video I talk about the the tank usage, then go on to talk about hoses which gets me to the Waste Master, and then I do the install of the Waste Master and dump our tanks. Seeing the entire thing is 35 minutes long, in the beginning of the video I tell the starting time of each section. As such, you can jump to the part that interests you.  Enjoy our waste.

29 thoughts on “Black and Gray Tanks and Waste Master Install

  1. Dave Wettaufer

    I’ve been using the original Drainmaster system for more than five years now. Our 2007 Carriage Carri-lite was factory equipped with Drainmaster’s 12 VDC electric dump valves. Unfortunately when the factory did the plumbing to the black valve they managed to crack the flange that’s attached to the Drainmaster valve, resulting in a slow leak which eventually made itself known. That’s when I contacted Doug at Drainmaster for a replacement flange and ended up purchasing the entire cam lock hose system. (I did a video on my retrofit and am amazed it has had over 8000 views over the years. Maybe the RV sewer hose is more popular than we think!) It’s a great system. I know Doug worked a long time on developing the system and I’m happy to see he was able to get a deal with LCI. However, no matter how good the system is, my wife still won’t dump the tanks.

  2. Frank C

    I bought the WasteMaster some years ago before they sold to Lippert . It has been a great trouble free system.. Just a quick thought , if you have a mostly full gray tank you can rinse the black after empting it by closing the hose end valve and opening the gray valve . Both tanks will seek to equalize their level and partially fill the black tank . Now close the gray vakve , open the hose end valve and proceed to empty the partially filled black tank . Now empty the gray tank as you usually do . repeat if you want to or say Job Done ..
    Thanks Dave for another good and helpful video ..

  3. Steve and Karen Fischer

    The new system looks very interesting and worthy of additional investigation. Just one thought, however. What would happen if the CG’s sewer connection was recessed into an area where you couldn’t attach that large bulky hose drain end coupling? I don’t it wouldn’t be a common occurrence, but I have been to CGs over the years in which this happened. When that happened, it was simple to remove my hard plastic 90 degree “L” and put a rubber doughnut onto the end of my hose, then compression fit the doughnut into the CGs pipe. With this system, I see no way around that. Not a criticism, just a thought.
    Good video.

  4. Steve and Karen Fischer

    Dave I was doing further investigation on Amazon and see that LCI now makes a standard bayonet to cam lock converter for those who do not want to cut the tabs off of their existing system. I know, it defeats the idea of the cam lock, but it might be an alternative for those who are nervous about making a permanent modification to their existing plumbing.
    Here’s the Amazon link:

    1. David.B Post author

      Hi…You must have missed that it is not a permanent change. You can alway put it back by replacing the Y as was mentioned. Also, that fitting is one the brings you BACK to bayonet and not the other way around. Note it has TABS, the things you need to cut off. :) I mentioned the use of this fitting if it was needed.

  5. Gary Gallerstein

    Dave & Brenda; This is simply a thank you VERY VERY MUCH for all of your ‘Pearls of RV Wisdom’ that we’ve learned thru your posts and videos for which Laura & I have benefited GREATLY. We’ve been ‘full-timing’ in our Tiffin Phaeton for a total of 18 months and still going strong. We first met you both, soon after we started RV’ing, when we were camping across from each other at the Grand Canyon National Park. (you very kindly pointed out that our front tires were lifted off the ground and this wasn’t good…)

    When we started RV’ing we didn’t know anything… not even Class A from B,C or even what black/water was, Really!! But with lots and lots of studying, time and your excellent instruction we have come a very long way!! I think we’ve read and watched all of your presentations. We’ve installed your recommended Mi-Fi system, Dyson Vacuum cleaner and now a Waste Master drainage system, and SO MUCH MORE.

    Thank you very much. We are a lot further ahead and able to enjoy our traveling around the country visiting all the national parks so much more because of your time and effort!!

    You both provide a wonderful, much needed, and MUCH APPRECIATED service to RV’ers!

    Best to you guys
    And again, THANK YOU!!


    1. David.B Post author

      Hi Guys….Very kind of you. Glad you find what we do of help as we do enjoy helping others enjoy their time on the road. What a way to live! Come join us in Quartzsite this year for OOBerfest! (If in the area of course.) Click the OOberfest banner at the top if you do not already know about it.

  6. Ted & Kathleem

    I have tried using many types of hose options. I now use a macerator as my primary option. I find it to be cleaner and less prone to issues than any option thus far. Have you considered this an option? If so, what do you see as the pros and cons?

    1. David.B Post author

      Hi…We had one and removed it because it can not PULL the solids from the tank. The big suction that takes place when you open the 3″ value is what is needed. Seeing it down not have that kind of draw power, solids are left in the tank and build up.

  7. Dave Wettaufer

    Dave I see your fresh water hose reel in the photo. That is something I am looking around for. Can you tell me what brand of reel it is and where it can be purchased? Is it powered? Any other comments about it would be great. Thanks!

      1. Dave Wettaufer

        Hi Doug, thanks for the link. I’ll check that out. I’ll have to decide if I really need an electric operated reel with one more thing that could go defective, or if a hand crank reel will suffice.

  8. Smitty

    Check out this Microbe product for your tanks. Very interesting all the different uses for Microbes on the web site: From fire fighting, to RV tanks! I’ve just started using it and I can say the toilet bowl is sparkling, so I assume the tank is too.

  9. Iggy Konrad

    I have 2 concerns, 1) I often need a sewer hook up that is only 5ft long as I often can park close to the sewer inlet and it seems the WasteMaster is too long and will have to be snaked around. 2) I’ve been to sites that had concert bowls around the sewer inlet, I assume to hold overflow, that makes it almost impossible to connect a sewer connections like the WasteMaster has. The concert side walls prevent my current drain outlet, the Valterra Sewer Adapter, from sitting fully into the sewer connection because the arm that connects to the drain tube hits the side walls of the concert bowl. This results is leakage but the bowl does collect most of it. The cam lock system does look very nice.

    1. Doug

      Hi Iggy,
      1. The Waste Master hose itself the collapsed position is only 5′ long. You only extend what you need to get to the sewer inlet. The WM hose does not snake around during dumping at any length up to its full 20′ extended length.
      2 To eliminate these “unusual situations” you can remove the sewer inlet donut on the nozzle, the barrel has threads on it. You can take a short length 12″ of your old hose, thread it on the nozzle barrel, then insert the hose into the sewer receptacle the nozzle on the ground beside the the inlet and open the nozzle. We recommend yyou put some paper towel under the barrel/hose interface to catch any small drips. Someday we hope most all RV sewer ground inlets are standardized so we can eliminate this issue all together.
      Glad you like the Cam Loc system it is the “right” fitting set for dumping any liquid and over time the RV industry will adapt as more and more OEMs switch to this industrial standard!

  10. Robert Smith

    Thank you for the very funny but serious video and a touchy subject. I hate my bayonet system and I will look into the cam lock for sure. Travel Safe!!

  11. Ron Carlson

    David, I bought and installed this system and was very pleased with the results. However, on our second trip since installation I noticed a leak in the hose. Closer inspection showed a small hole near one of the green rings. I think there is at least one more but I will not know until I unhook. The hose has not been abused. I hope they will replace it. What do you think/


    1. David.B Post author

      I find that shocking and kind of hard to believe as each hose setup is tested with 10PSI of air pressure after it is all assembled. I am sure it would be replaced and I am sure they would want to know. It really makes no sense.

        1. David.B Post author

          No need to send me a video as I did not sell it or make it. :) I would get in touch with whomever your purchased it through and get it replaced.

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