Thursday, March 19, 2009

Thursday Tips: Creative Sanitation

Tuesday's post garnered a comment about, umm, sewage that I feel needs to be shared here in the main blog, for two reasons. First and foremost is that I don't want anyone reading here to make the sort of mistake that is alleged in that comment, especially if they got the idea here in the first place. Second is that I want to be sure no other readers have the same misunderstanding of what happened as did that commenter. That said, if talking about (and photos of) sewage and dumping of RV waste tanks is not your thing, feel free to skip the rest of this post.

The comment specifically addressed this statement in Tuesday's post:
... this particular spot was just 20 yards from Freightliner's city sewer connection, and ... my macerator hose end ... fit in the pick hole on the manhole cover ...
To which reader Leland responded:
Sanitary sewers are sealed, pressurized systems, if you found an unsealed cover it is access to valves and pumps now covered with .....
First, let me say that, having overseen the construction of a dozen or so major buildings, right down to the sewer connections, I have more than a passing familiarity with sanitary sewer systems. I am not sure where the impression is coming from that sewer systems are sealed and pressurized. While there are, indeed, some types of sewage transport pipes that happen to be pump-fed and thus pressurized, this is not true of the vast majority of the sewer network in most cities. Sewers almost universally work by gravity alone, at least until there's no further down that you can go, at which point a "lift" or "ejector" pump is used to move the effluent back up to a higher level. These systems are not pressurized, and, in fact, rely on open venting to the environment at periodic intervals to avoid hydraulic locks in the pipes.

This is one reason that every few hundred feet or so there will be an "SSMH" (sanitary sewer man hole). Sewer manhole lids, BTW, are also never sealed or tight-fitting, and usually have extra large "pick holes" (so called because manhole covers are removed with a bent iron bar called a "pick," and this is where the pick is inserted to remove the cover), for a very important reason: Sewer gas contains methane, which rises and needs to escape from the manhole. If methane is allowed to build up in the manhole, a spark (from, for example, an iron tool, or a passing vehicle) can ignite it and cause an explosion, which can easily eject the ~300lb manhole cover hundreds of feet. People can be and have been killed or injured by such flying manhole covers.

There are dozens of different kinds of manholes; many contain electrical wires, water mains, natural gas lines, telephone cables, fiber optics, or cable TV lines. I have spent more than my fair share of time in many such manholes, including sanitary sewer ones. Some manholes also lead to "storm drains," which are sometimes confusingly called "storm sewers" although that term is not really accurate. To avoid confusion, sanitary sewers are usually referred to by that term explicitly, and manholes for sanitary sewers are usually marked SSMH or SS, and sometimes just Sewer, which is how they are marked here in Whittier.

Sewer manhole in front of Freightliner

If you are going to dump into a sewer manhole, you had best be absolutely certain that the manhole you've found is, indeed, a sanitary sewer. It helps to know not only how they are marked, but also generally how they are designed and laid out. But the last step must always be a visual check. If there is a pick hole large enough to insert a hose, then it is large enough to see inside. The trick is to wait until it's dark out (your eyes will never adjust enough in the daylight), cram your flashlight into one pick-hole, and put your eyeball up to the other one. If you don't see sewage, it's probably not the right kind of manhole.

This is much easier with the naked eye than with a moderate-priced digital camera, but I attempted to capture a picture of the aforementioned manhole this evening. The super-bright LED flashlight that I used Monday puts out a too tightly focussed beam, so I had to resort to a Mini-Maglite I had lying around, and set the camera on manual with as wide a shutter as I could get. It's blurry, because only the lens fit in the pick-hole, and the autofocus window was obscured:

Inside view, as seen through the pick hole

The city lateral flows from right to left in this photo, and, yes, that's raw sewage (toilet paper, I think) in the right quarter of the shot (timing is everything). The connection from Freightliner comes in at the top of the photo; note the channel is "sweeped" in a curve toward the direction of flow. To the left is visible the bottom rung of the built-in ladder, obscured by the shadow of the top rung. As you can see, the sewage flows "open" in the bottom of the manhole, but there is a "floor" level that normally is dry. When sewers run heavy, this floor will sometimes be under water -- you can just make out that the floor level is below the tops of the sewer pipes. Nevertheless, I try to get the hose to land in the "channel." Those "dots" all over the floor are, yes, cockroaches.

Now, the legality of emptying effluent into a city sewer system is another matter entirely, and I'm not really going to get into it here. Suffice it to say that sewers are paid for by the residents and businesses in a city, and fees are assessed for their use. It is generally best to utilize the sewer system on private property with the permission of the owner, who is paying the fees.

We generally try to do this whenever possible. We will hunt around for what is known as a "sewer cleanout," usually a 4" or 6" diameter pipe which rises vertically from the building's underground sewer connection to the city lateral.

Graphic: City of Santa Clara

Cleanouts sometimes stick up through the grass or shrubery right next to a building, but more commonly, they are in the driveway or parking lot, recessed a few inches into the ground, and covered with a heavy iron plate called a "traffic cover" (so named because it supports the weight of vehicles driving over it).

Image: Genista

The cleanout pipe itself will have a threaded PVC or metal pipe end on it as well, which must be unscrewed with a wrench.

Image: State of Hawaii

Once again, you must be certain that the pipe you are unscrewing is a sewer cleanout, and not, for example, access to water or irrigation valves. The traffic cover, if any, will usually be marked "Sewer."

We prefer these, both because they are on private property, thus avoiding any legal issues, and they are large enough to accommodate our regular sewer hose. Dumping is just as easy, just as fast, and utilizes the same procedure as at a regular dump station (however, do not use a threaded or other "tight" coupling -- the cleanout is not, itself, vented, and you'll need some room around the hose for air to escape the pipe). Freightliner has one of these, but, as luck would have it, it is right smack in the middle of their main entrance to the service department -- a very busy driveway indeed. The manhole I chose happens to be where Freightliner's connection to the city system is made, and so my position is that I used Freightliner's sewer connection. (As their customer, to the tune of several thousand dollars when we are done, I have no moral qualms about using their sewer connection, just as I used their spigot today to fill the water tank.)

Dumping our tanks into sewage connections that would otherwise be inaccessible to us is the key reason why we have a permanently installed macerator pump on board. While we have traditional gravity dump valves on the left side of the bus, with 3" terminations for both black and gray water (it would take much longer to empty our 135 gallon gray tank through the more common 1-½" valve), we also have additional 1-½" gate valves on the curb side of the coach leading directly to the macerator. A "garden hose" fitting underneath the coach allows us to connect a ¾" diameter, 50' long rubber hose we keep separate just for this purpose (note: do not mix up special macerator hose and fresh water hose!).

To date, the macerator has come in handy mostly in Mexico, where the Mexicans have cleverly located dump stations 30' away from the closest place you can drive, and sometimes up hill to boot. The macerator pump will, indeed, allow us to pump our sewage uphill. But it could also be used to pump out into a household toilet, for example, or a sewer cleanout too far away or too high for our gravity hose to work, or a vault toilet in a primitive campground. Or, as we've now discussed, through a small pick-hole in a manhole cover.

The problem Monday was that the heavy brass end on our super-duty rubber hose has hexagonal wrench lands on it, and those would not fit through the pick-hole. While the end would fit in far enough to, umm, spray sewage into the manhole, that's rather discourteous. I wanted to be able to get the hose down the 5' or so to the actual sewage troughs in the bottom, and so I bought a cheap 5/8" diameter hose (which slowed things down a bit -- the ¾" hose is faster) with an even cheaper stamped-metal end on it (which I was prepared to cut off, if necessary), which slipped right through the hole.

So there you have it -- a more detailed explanation of Tuesday's post, and a primer on creative RV dumping as well. Complete with graphics and a mildly disgusting photo; oh, the things I do for an informed readership.


  1. Hi Sean:

    An excellent article on sanitation, it will educate some folks on how these systems work.

    We use our macerator pump in Mexico as well, it also reduces the "solids" pressure on the systems they have down there.

    I also note that the phrase "man hole" has been replaced by the phrase "maintenance hole" in some recent drawings to satisfy the politically correct zealots out there, it has the advantage of not needing to change older drawings when the MH short form is used.

  2. Very informative, we usually try to use a dump station, but this is a great primer on emergency measures.

    Thanks for taking the time to write it all up.


  3. I hope you sanitized MY camera after taking that photo...

  4. Geez Louise. A poor guy just never knows when the wife is watching.
    Anyway....I was kinda wondering about that whole "pressurised" thing. Pretty much figured somebody had been inhaling a little too much methane. (or as the Brits might pronounce it , "meethane")
    The basic elements of sewer systems are the same all over the world, with gravity being your biggest friend.
    Thanks for the tutorial. Took considerable effort. Your efforts are appreciated.
    Keep yer stick on the ice.
    Oh, and wash your hands.


  5. Sean:
    please dump ONLY in an approved location.
    once more you expound enough miss-information to show your ignorance... you know a bit about it but just a little bit. there is no way to tell if that is truly a sanitary sewer from reading the markings on the lid or even opening it up.

    please quit being the ugly American and put your Sh__ where it belongs.

    Folks: in most places a stunt like this could get you a pair of handcuffs and a huge fine (thousands of dollars) and would in my city just a couple miles from their.

    Put it where it belongs!

  6. Very thorough post, and believe it or not - quite interesting! Learned lots of stuff I didn't know.

  7. @Anonymous #2: Gee, Al, you sure woke up on the wrong side of the bed. How're things in Bakersfield these days?

  8. Generally, when people choose to post anonymously it is due to a lack of courage to be identified with their "comment". The "person" who wrote the anonymous comment really enlightened the rest of us to his obvious ignorance, and poor disposition. Your explanations, and irrifutable photographic evidenced shows you know what you are talking about, and he does not. Thanks Sean!

  9. My two cents. I am a Civil Engineer, and have worked with water and sewer systems my whole career. This post was very accurate.

  10. Hmmm... didn't a really bright philosopher once say; "Insults, are the arguments used by those who are wrong... and KNOW IT?"...

    and I ain't anonymous!

  11. I was just reading back a bit on your posts Sean and wanted to thank you for this one. I always wondered what was under those Sewer covers. About 100 years ago when I was going to university they were the entrances to the Engineers' lounge and we used to paint that label on them to help the Engineers find their way home. But I had to assume that there couldn't possibly be that many engineers' lounges across North America so I have always wondered what was under the other ones.

    I don't know how to tag this with my name so I'll do it this way:
    R.J.(Bob) Evans

  12. In the City of Atlanta, only 'force' mains are under pressure. These are used to pump sewage from a lift station against the hydraulic flow. All commercial and residential connections are made on gravity systems (You know the saying - "shit runs down hill").

    Sewer charges are based of the monthly water meter bill. Logic is what went through the meter will be returned into the sewer. We recommend separate meters to be installed for irrigation systems.

    You can usually determine the difference between Sanitary and Storm sewers by looking in the manhole. Sanitary sewers will be wet as there is usually flow. Storm will be typically dry depending on the weather.

    Probably not a good idea to get caught dumping into a city manhole - Probably land you in jail.

    Good article.

  13. i must say sean knows his shit!!


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