What happens to the "stuff" falling down in a vertical pipe in a skyscraper? The answer:
The problem with wastewater running downhill and picking up a lot of momentum isn't as severe as it might seem. For one thing, flowing water tends to adhere to a surface, such as the inside of a pipe, and the friction slows things down considerably. There's also the phenomenon known as "terminal velocity," which skydivers are familiar with: after you fall through the air awhile, you reach a maximum speed. For water inside a pipe, this usually comes out to around 10 to 20 feet per second, depending on the diameter of the pipe and such.I love "and such".
3 comments:
As the article points out, the challenging technical question is not how you let the water down (since gravity takes care of this nicely), but how you let the air in to replace it (venting). Recently I had to replace a sewage ejection pump in my basement. There is a utility sink down there below the level of the sewer main so the waste water has to be pumped up maybe 2 meters. I found a very nice French made submersible pump with small holding tank and float valve - a one piece unit that you just plug in, very easy to install. In order to allow air in, it has a very simple and reliable one way air admittance valve at the top of the sump chamber which allows air in but no odors or water out. This valve suffices for venting under EU codes. However, according to American codes you are supposed to cap that valve off and install a large diameter vent pipe (equal to the size of the waste pipe) going all the way to the roof of the building to allow air in. Needless to say I did not follow the code (and since plumbing inspectors do not visit private homes unless you ask them to, no one is the wiser and the pump operates flawlessly). If you multiply this by millions of homes, many millions of $ are wasted on obsolete requirements like this (and even more millions are wasted because the roof penetrations for vent pipes often leak and cause damage). Plumbers must like this because it adds greatly to the cost of the job.
K
I dont recommend those small pumping units. if it fails, you have a flood in the basement, mold, odor.
What is the alternative (other than no sink at all) if your floor level is below that of the sewer? In any case I MUST have some sort of ejector - my HVAC unit is in the same room and produces condensate water (summer and winter) which must be pumped up somehow. Pumping it directly to the outside is not permitted because the line could freeze in winter.
There's no toilet down there which is much harder on pumps. The last pump which this one replaced looked to be maybe 40 years old and I had it for almost 20 with no problem until the bearings on the pump finally wore out (and this was a crude cast iron unit, not a modern stainless submersible)
The only possible "bad" failure mode would be a multiple failure (which is not impossible but is rare). The main sewer line would have to become completely clogged and backed up, sending sewage down the ejector line AND the check valve on the ejector line would also have to fail. It is possible but it is also possible to be hit with a meteor - I'm not worried. We had over 60 cm of snow here yesterday - that's more worrisome. Some buildings roof collapsed from the weight of the snow and I've had leaks before in my house when the snow begins to melt - the roof system is not properly engineered for that amount of snow.
K
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