How to Drain an RV's Black and Gray Tanks.

My girlfriend and I  recently bought an RV. We bought a 1990 Holiday Rambler Alumalite tow trailer. It's about 27' (or about 8 meters) long. This being our first RV, we knew nothing about how to operate or care for it. We bought it with the intent to become full-time RVers and have been living in it (comfortably) for about 2 months now. One issue we ran into quickly was how to drain the tanks, after searching online I found nothing for this specific model and very little for any other, so here is my instructable for how to dump the gray and black tanks.

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Step 1: Overview and Materials

 I will be showing you where to find the drain valves, how to attach the hose and drain the tanks, how to clean the black tank and also some of the tools I use to do this with. 

I use

Gloves - preferably rubber or anything that won't let water or "yuck" through.

A wand - a length of cpvc pipe with a valve used to put into the toilet and rinse the tank.
                 The picture of the wand is easy to miss - it's next to the detergent.

Sewer hose - a special hose used to drain RV tanks.

Female to Female (not as interesting as it sounds) - a female to female garden hose adapter used                                                                                                 to connect the hose to the wand

Laundry detergent - powdered laundry detergent (the cheaper the better) I have read on several                                          forums that the detergent helps break apart the waste and decrease smell,                                            and it seems to work very well.

Hand sanitizer - for sanitizing your hand as often as you need!!

I also use at our present location a portable waste tank - because there is no immediate sewer                                                                                                                 hookup available.

Step 2: Find the Valves

 On our RV the valves are on the backside towards the rear, on most RVs I have noticed that it is hard to miss. Look under your Rv for a large pipe and some handles. Ours is easy to find and plainly labeled "Waste Water" for the sinks and shower (this is also known as the gray water) and "Sewage Water" (also known as the black water).

Step 3: Attaching the Sewer Hose

 Remove the cap from the Drain pipe by twisting (most likely counter clockwise). and attach the sewer hose by twisting the channels around the protruding plastic pins on the pipe.

Slide the other end of the pipe into the sewage connection in the ground or into your portable tank (this connection does not lock in but rather slips).

Some may have the locking channels on both ends for different types of connections, some amount of analyzing may need to be done to make sure that you have the proper fittings for your particular situation.

Try to make sure that the hose drops elevation from your RV to your destination (becomes lower).

It is also a good Idea to support your hose so that it has good downhill flow. There are products sold for this but I have found that a board works just fine, and it was free.

Pull your sewage valve open and let it drain for a few minutes. I usually let mine go until I can't hear water flowing through it.

Close the valve. If you are connected to a sanitary sewer line (!!! NOT A STORM SEWER !!!) then proceed to the next step but  if you are using a tank like I am then I have added some extra steps at the end of this intractable for how I dump the portable tank.

Step 4: Clean the Tank

After dumping the black tank be sure that your valve is closed.

Some people just fill the tank and then dump it again but for best odor control and to prolong the life of your tank it is best to rinse it with a wand, or something that will break solid waste and toilet paper free from the walls.

I rinse the tank by:

Turning off the water pump.

Opening the toilet and pouring about 4 cups of laundry detergent into the tank.

Then I use the wand to rinse around in the tank until I see that the water level has risen to the bottom of the pipe leading from the toilet to the tank. ( I made the wand out of 1/2 inch cpvc for about 4 dollars)

After rinsing the tank, pull open the drain valve and allow to completely drain.

When the tank is completely empty add a tank deodorizer and follow the directions for that product. We use a deodorizer that contains no formaldehyde (we have read in many forums that the formaldehyde can damage the rubber seals in the tank).
Close the drain valve, remove the hose and replace the cap. Now you have successfully drained and rinsed your tank.
I usually have to do this once a week. Every three weeks I do this twice (not sure if it's necessary but it doesn't hurt).


Step 5: If You Have a Portable Waste Tank.

 If you have a portable waste tank like we do currently, then there are some extra steps.

This step is more of an overview of how we do it rather than a "how to"

Our tank drains from the broad face rather than the thinner bottom, this in combination with where we have access to drain it forced us to create a way to elevate the tank. 

To elevate the tank we installed a pulley system which uses a metal ring at the bottom of the storage building, a pulley at the top and a cable puller and some rope to connect it all together.

These tanks are very heavy when full, I weight about 280 lbs. (127 kg) and with my entire weight on the other side of the pulley we could barely get the tank moving, so I would guess that the tank completely filled would weigh at least my weight. The point of mentioning this is ---SAFETY---, use only rings, pulleys, ropes and pullers rated for for the appropriate weight, everything in our system is rated for 400 lbs. (181 kg)

We have extended a pipe from the sanitary sewer to just outside the house. 

First with the tank still flat on the ground I remove the large cap from the tank and the sewer line from the house and attach the sewer hose to both,

I then lift the tank vertical and attach it to the rope (leaving the smaller breather cap on until after it is vertical and attached) then I remove the smaller cap so that the vacuum from the move starts a syphon and begins to drain the tank.

As the tank drains I lift it with the cable puller until it's as high as it will go, I drain until empty, and then lift and drain the excess in the hose.

After the tank is empty I attach the hose to the breather port and rinse the tank well before storing.


Step 6: Warning/Safety

This instructable involves human waste and elevating dangerous weights. Please do not do anything that you are uncomfortable with. Please do your research and find out what weight your tools can handle and the risks involved with being exposed to human waste. I am not an expert my advice is just that, advice, based on my own experience. Thank you for reading and good luck. 

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    13 Discussions


    10 months ago

    I also have a Holiday Rambler. Always drain the black tank first, then drain the grey water. That way, it cleans out your hose before you detach and store it. After all, the grey water is basically used, soapy water anyway, Waste not, want not...


    1 year ago

    I love it. Thanks for sharing!


    Question 1 year ago on Introduction

    I just purchased a 1989 alumn lite co. Holiday gambler I think! It' rough but plans are to restore it. If anyone has info about these campers it would be appreciated.


    2 years ago

    Thorough, well-illustrated, clear instructable. Well-done!


    Reply 2 years ago

    It is probably the converter that charges your battery while plugged into power. Mine does not work so I have to use a charger to keep it powered up.

    Please leave any improvement ideas, suggestions for deodorizers, or just general knowledge of the subject. I am not an expert and always appreciate learning a better way to achieve my goals.

    1 reply

    I have kind of a unrelated question, I recently got a Holiday Rambler travel trailer, close to 30 foot long and supposedly a 1993 aluma lite model, I'm not 100% sure though, I have a couple off topic questions for you, I plugged it in and there is a humming underneath the front (toward the tongue) about 4 or 5 feet back in the center underneath there was some kind of panel and that was where the noise was coming from, I got the noise to stop by turning off one of the breakers, but I would like to know if something is on that I can shut off, because until I find out I have no ceiling lights because that breaker is off.. the A/C is off and I think the heat is off since it uses gas. Since I really know nothing about the model other than it saying Holiday Rambler and Aluma lite on it, my question to you is, is there a place, a tag or something located in a common spot that has information on the trailer?


    4 years ago on Introduction

    Need help regarding draining black tank on a Dutchmen Aspen Trail travel trailer. It is not moveable. The sewer tank to dispose it into is about 40 feet away. It is also slightly elevated. Does the draining only work with the help of gravity, or is there an way to force the contents out, in spite of a slight elevation?



    6 years ago

    I've heard if you are traveling and want to clean your tanks, dump some ice down the toilet and drive... Cleans up the tank nicely


    8 years ago on Step 4

    Some RVs have a pump called a mascerating (spelling?) pump that is sort of like a high powered blender so that there are no solids in the tank at all. It might be a good idea to have that special pump. I believe that some rigs also use that pump to force the waste to dump.

    1 reply
    Lonnie Wglorybe

    Reply 7 years ago on Introduction

    I know this is an old thread, but a mascerator fits on the drain of the tanks. It only "blends" the stuff as you drain the tank. It doesn't do anything to the stuff going into the tank.


    8 years ago on Step 4

    this seems like a no brainer but i had a hell of a time draining my tank. definately gonna make myself a wand like yours, as well as use the laundry detergent, thanks!