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Automatic BlackTank Vent

First, I want to present the concept: I have invented so many things, and I suppose, this is another one. I am the first to do this.

The standard residental commode has a PTrap, or U shaped collum of water to isolate sewage smells and gasses. But the residental commode is water hungry, and is not suited for the RV.

The RV commode, on the other hand, only has a small amount of water in the bowle, and it is dumped directly, straight down, into the BlackTank. A mechanical valve shuts off the smells and gasses from coming up into the RV through the commode. However, during the time that the valve is open, sewage odors can come up from the BlackTank. This is especially noticeable if the bathroom has a bathroom Vent Fan running in the Draft-Out mode. In this case, the bathroom fan not only throws out bathroom air, but also sucks bad smells up from the BlackTank. The return air is permitted through the black ABS Vent Pipe.


Here is the intire path for the process:
Fresh air on the roof, goes down the ABS Vent Pipe, into the BlackTank, across the water, up through the commode, and into your nose, and eventually out through Bathroom fan.


No smell will come up until a user uses the DumpValve. An open DumpValve allows air flow in a negative way. Despite the fact that MaxAir Fans, and Fantastic Fans can produce a lot of draw, most professional RVers experience little odor.

Many RVers know how to maintain their Tanks. It is a science, and unfortunately most RV information is wrong. We have been RVing for over 10 years, and do not experience much odor. I have recently viewed the inside of my BlackTank. There is absolutely no buildup on the sides or floor. I never thought that I would describe the inside of a sewage tank as beautiful.

The owners of multimillion dollar coaches have a problem that no one has figured out how to solve. I have seen it with my own eyes. It is a disgusting and smelly plague more common with expensive rigs. From the diagram above, the owners leave the DumpValve attached to the hose, and leave the DumpValve OPEN. From the diagram, you will see the parks sewer gasses, from large communal underground tanks, travel up through the sewer hose, into the BlankTank, and up and out the BlankTank Vent, located on the roof. This forms a completed path with lots of air flow. This is important. There is lots of air flow! The gasses and odors leave the Vent area on the roof, and flow down the sides of the RV into neighbor's yards. The sewer hose itself, as well as the BlackTank are contaminated with communal pathogens. There have been no studies specific to RVs, but many studies on COVID, and pathogens in general, in communal sewage. In fact, all around the world, it has been a great measurement tool. A solution to the Big Rig problem may involve the training of humans. Or, the purchase of an RV certificate, if you have enough money.

My rules:
Never ever Winterize with fluids in any Tanks.
Never ever use cleaners in any Tanks.
Never use chemicals in the Fresh, Gray, or Black tanks. The Fresh can contaminate the Black.
Use plenty of water in the BlackTank. Initially and throughout.
And Nicola Tesla says to drive around the block three times before Dumping. Why three?
Use and cherish microbes, enzyme catalysts, and bacteria. And protect them!


No matter the care of the Tank itself, there remains a possibility of odor on high travel days, and even with wind.



There is a better way. And I invented it.




-25% $8.99 Amazon
80mm or 3.1 inch Fan Made by GDSTime.
12 volt; 0.2 Amp; Rated Speed: 2800 RPM;
Air flow: 43.6CFM; Noise:31dBA; Power: 2.1Watt
Bearing Type: Sleeve Bearing


Desired is high RPM 2800 RPM to create static pressure, not Volume.
Desired is high wattage 2.1 watt, and high incidental CFM Volume.



I have designed a system using an automated fan. The fan creates a low pressure inside the BlackTank. At this point there is no air flow, just a low pressure in the BlackTank. But just as soon as the commode Valve is opened, air is free to move from the inside of the bathroom, down into the commode, into the Black Tank, and out the BlackVent pipe. Odors can not invade the living space.

We can not leave out the human factor:
Non of this would work without the MotionDetector. No one can remember to turn on a vent fan, much less to turn it back off. Although there is plenty of idle time to think about it while on the pot, humans can not reliably do this.

I have chosen this engineering approach to solve the odor problem rather than the political. Believe it or not, there are politicians that can legislate away bad smells. But I am not one of those that can wave it away with a piece of paper. Nor am I like the Pope, that can ride in a trailer without making any poop, in the first place. I have a solution that has not been attacked by building codes or politicians.




There are a couple of ways to run a wire up on the roof. One is to come up through the Refrigerator Vent. But a novel way is to come up through one of the Tank Vents. And how convenient; That is just what I am working on. I guess that I will be the first to do this. Although it is unheard of, there is nothing wrong with it. Here I have tied off the wire so that it does not slip back down the ABS pipe.

The black ABS pipe that vents to the roof has an outside diameter of 2.0 inches, and it has a 1.5 inch inside diameter. But there are three measurement schemes for ABS and PVC. One is the outside diameter OD, ID, and Nominal. None of the three are the same, and none have a reference to a standard tape measure. It is like 2x4 studs not having dimensions of two inches or 4 inches. It is just what they are called. It is a name given to this type of lumber, and has no reference to actual measurement.

I had gone to the hardware store and grabbed a "two inch" elbow. When I returned up on the roof, I discovered the elbow was way to big and sloppy. The elbow came out of the correct bin at the store because it had a "2" printed on the end. But measuring with a ruller showed 2.35 inches, inside diameter of the elbow. Also, "2 inch" ABS pipe at the store reads 2.3 inches OD. I would hate to be a plummer because Names of pipe and fittings, and Measurements of those pipes and fittings have nothing to do with each other.

This elbow in the picture is labeled a 1.5 elbow. It has a 2.0 inch ID and fits good over the 2.0 inch OD black ABS pipe sticking up.




Down below in a cut-out of the wall, you can see 1.5 inch black ABS Pipe. I have drilled a whole into the pipe. I have fed the 20 gauge wire into the hole, and retrieved the wire coming out the top of the ABS vent pipe on the roof. I have sealed the hole with white adhesive caulk. The caulk has to seal very well. We do not want odors in the living area, howbeit in a wall.










My first idea was to simple come off the Vent with an elbow, and go some place else with a box.
But it is not going to work, the elbow sticks up too high.




My first idea was to simply get away from all these solar panels. You can do this with a long pipe. You have to get away because the box is way to high with its shadowing to be near solar panels.

Once away, in addition, I thought that I would mount the fan with a tilted floor. That way, rain would run back out and away from the fan. But, a mute point. This will not work do to hight restrictions.




But this idea will not work. The box is too big for ANY WHERE on the roof. And I can see the the stupid looking 1.5 inch black ABS elbow and pipe sticking up on the roof. I can stand back from the trailer and clearly see some kind of contraption on the roof. I would rather be only thought stupid than to provide clear evidence.




Here is a better way...
Take off the top and bottom boards. Replace the top board with a very thin plywood cover. The box will slip directly over the ABS vent pipe. The pipe will come up from the bottom of the box. The box will have to be modified a little to slip over the plastic roof-housing. Solves a lot of problems. K.I.S.S.




Just to test out the idea, the box is sat over the pipe. The profile is much lower and will not shadow a panel too bad. Here the orientation is wrong, facing to the left, instead of facing backward. You want to form a natural draft when going down the road. You do not want to blow air down the ABS Vent Pipe. A dormant box needs to face backwards. So I will have to move a panel.




Here is inside the box. There is enough room above the open end of the ABS pipe and the top of the box. Looks to be about an inch. The fan will suck air up the pipe, and will be diverted by the box ceiling before the air heads out the front of the box.




This is the orientation that I want. I need to moved a panel to the back and opened some space. I have made a little "awning" at the front of the box where it is open.

A 2% shadow will kill the intire panel, sense all cells are wired in series. So the shadow of the box opening is quite severe. But that is Ok. This panel is only a 30 watt panel; the very first panel that I bought, some 10 years ago, for this RV. I am an engineer, and I have never calculated how much wattage I have on the roof. But I know I can do 600 watts. So, the 30 watt panel is a minor sacrifice.

But the other panel to the left is a 100 watt panel. I do not want to loose that. I should be OK with the box having a sloped roof. A sloped roof favoring this panel.




I know that the concept will work. Its getting too hot to work on the roof. I will finish roof work tomorrow. I will now go down below, and work on the motion detector.




Down below in the bathroom of the RV, I have the Motion Detector opened up. The motion detector is a 12 volt, Relayed, 360, Socobeta PIR. $11.39 from Amazon. No reviews, but this thing is real nice.

There is no way - for sure - to know which way the wires go. The information is on a tiny piece of paper, and it is only in Chinese. But I am an engineer and do not need to be informed of this information:
Standard nomenclature in the US is for Red to be the 12v, Black to be Ground, and Yellow to be the Output. Upon taking the Unit apart, I can see that this is correct. The Yellow comes from the Relay, and its trace is heavy going into the relay contact and heavy leaving the relay contact going to the yellow wire. Yellow is a relay switched Output. For sure. The Black goes to a Negative side of an Electrolytic Capacitor. Obviously the Black is Ground. For sure.




A photocell can be seen at the lower right side of the PIR. (It has a red serpentine feature in an oblong can.) That is not a good thing! The PhotoCell can stop the Motion Detector from working in the daytime. I covered the cell with two layers of tape to block any light from hitting it. I probably should have used caulk, as the RV is going to take a lot vibration. They have an indicator LED at 10:00 of the PIR. If they keep it dim, it will be OK. Everything looks OK. i like this company.




I mounted the MotionDetector beside the light switch. I had good access from the inside of the wall.




There are two adjustments:
The bottom adjustment, called Lux, disables operation in the daytime. Which, of course, is bad use of a motion detector in general. It should operate in any light level. While I had the unit tore apart, I blocked the light sensor with tape. Some light still got through, and I had to rely on this adjustment. Turning clockwise increases the light required to stop operation. Now, maximum sun coming through the skylights does not stop the motion detector. Perfect!

The top adjustment is for the Delay.









In the wall, I have access to everything, all the wires and connections, behind these two panels.




The first thing that I did was to put a courtesy light on the toilet paper.
The wire that goes to the fan on the roof is the main event.
This toilet paper light is only an coincidental auxillary function.

Anytime someone is in the bathroom several lights will come on. All these lights are only an indication that the Black Tank Vent Fan is on, up on the roof. Other inventions are only "spin offs".

I have to chuckle. Not even the big boys with multimillion dollar coaches have a Toilet Paper Courtesy Light. Now, how special is that?




Also, I put two blue light strips along side one of the towel bars, for no reason. They are just pretty. Well, there is a reason: they let me know the fan is on.

On the right hand wall, you can see the motion detector mounted next to the switch for the main bathroom lights. No wires show, and it is perfect. Works perfectly.




Also, I put a bright white light strip under one of my shelves. It is hard to see because the sun is coming in the front door. There is more ambient sun light from two skylights from above. There is plenty of light for sitting on the pot, day or night, despite the fact that this is not the purpose.

I did a quick test:
I lit a piece of paper, and held it burning over the commode. I opened the dump valve, but could not see that the smoke was going downward. I was hoping the smoke would be drawn down into the commode. I thought of inviting a cigarette smoker into my trailer to blow a little smoke into the commode. But I quickly realized that this would defeat the purpose. And I do not know if the smell of cigarette smoke would ever get out of the RV. It might linger for a long time. So, that is a bad idea. Cigarette smoke killed my Mom and my Dad. No cigarette smoke is ever getting in my place. You would swear to God that the Pope and SnowWhite live in this RV.




Up on the roof, I can hear the fan, even though there is no air flow without the flushing of the toilet, and momentarily holding the flush valve open. Otherwise, it is only a static negative pressure in the tank. Seemingly, the fan works in vain against a brick wall. Seems to work perfectly.

"For my thoughts are not your thoughts, Nor my thoughts are not your thoughts, Neither are your ways my ways," declares the Lord. "As the heavens are higher than the earth, so are my ways higher than your ways and my thoughts than your thoughts." - Isaiah 55:7-9

But the only way to know for absolutely for sure, is to hitch her up and get to the lake. All it takes is a little nudge and a reason. Not too much of a reason; just a little reason. If it is not too much from me, perhaps it is God's reason to go to the lake.