Saturday, September 4, 2010

Instead of a Plunger, Use Bernoulli's Principle

Here in our Arizona home, we have not just one, but 2 bathrooms - a big deal having grown up in a Midwest house with only one. And working at home, for me the rest room is just about 10 steps away - not down the hall and past the boss's office in a public lavatory. And living in Arizona, and having kicked my Diet Coke addiction (too much fake sweeteners confusing my pancreas & brain, too much bone leaching phosphoric acid, too much reflux) I drink alot of organic tea, and a glass of Britta filtered water along with it. So at least once an hour, I'm making a short trip to the home-office-adjacent hall bath.

Now, since this is Arizona, and it's the Sonoran desert, we try to conserve water as much as possible. Low flow wash machine, low flow showers, etc. And since getting rid of tea from one's lower renal tract doesn't require a large amount of flush-able toilet tank water, I've installed several large glasses to act as displacement cylinders inside the toilet tank, reducing the over-all volume of water discharged. Works great for #1, not always so great for #2, when lack of toilet tank flow leads to a stopped up toilet.

So, a logical person could use a plunger, and for almost 3 years, I occasionally DID use a plunger to create artificially high pressure above the blockage, and force it down into the sewer. But then this year, I realized, just let Bernoulli do the work. No more nasty plunging. Instead, I toggle the handle of the toilet tank, to get the bowl nearly full of water. Now, all that water has gravity acting upon it, and it wants to find the lowest point - but there's a blockage in the way. *

*Note: Gravity always works in the same direction - except for those who don't believe in evolution (since it is a theory, and gravity is a theory too, and their both part of nature), so if you're a fundamentalist Christian[TM] you'll need to keep your plunger handy. This method won't work for you.

Now, given alot of time, and patience, the pressure of the water above the blockage, will gradually push down on the blockage at the bottom of the bowl, and the toilet will clear itself. But lots of people do not have time or patience. So, what you can do instead, is run water in an adjacent tub, or flush a 2nd toilet that shares the same sewer trunk line. The water rushing down the drain on the down-stream side of the blockage, will help to induce a lower pressure back there, urging the blockage (and the water in the toilet bowl pushing down on it also) to come join them in their journey to the waste treatment plant. No mechanical force necessary. Hands not dirtied using a plunger, no splashing or sloshing - it's an elegant leverage of science and logic over brute force, and I've employed this principle 3 times in the last month. Works sublimely0 well.

People think it's about "suction" in hydrodynamics, but "suction" is imaginary. There's simply areas of higher, and lower pressure, and they're all trying to get to equilibrium whenever they if they can. Nature abhors a vaccuum, and Bernoulli, back in the 16th century, proved it's all about differential pressure, long before anyone knew what molecules or friction were.

Yes, critics of this method might say "a properly vented toilet or tub would not share a common vent line to the roof, so your assumption is invalid" - but this is Arizona. The Home Depots have signs first in Spanish, and then in English. Subdivisions sprung up on reclaimed farm land 10 years ago faster than weeds without RoundUp[TM] on a non-organic farm, and many homes were slapped together with inadequate plumbing vents - each roof penetration costs money and time you know! Also, many older homes, especially those in large urban areas like Chicago, NYC, SF, LA, etc, are possible not compliant with "current Universal Building Code" and could benefit from the same patient application of Bernoulli's principle, rending millions of plungers obsolete.


  1. The start of your post talks about conservation of water and how important it is when living in the desert. But then you lead into a novel idea for replacing plungers by using more water, like by flushing a toilet or draining a bathtub on the same trunk line. The plunger is better at conserving water than the Bernoulli method.

    Also plungers don't just pressurize the blockage, they also create "suction", ie. an area of low pressure, behind the the blockage to help free it up by reversing the blockage momentarily. Plungers also can create an oscillating positive/negative pressure wave behind the blockage by somebody .. errr... plunging them up and down. There is no way for your Bernoulli method to do this.

    I like the idea, though I am admittedly surprised it works so well. But it seems to solve one problem at the same time making another problem worse (using additional water).

    Perhaps try raising the toilet tank high above the the bowl like toilets were originally in the old days, being actuated by a chain pull instead of a handle. The extra pressure head of the water might help flush the toilet better without using more water. I think some toilets use compressed air too now, so maybe that would be another way to use Bernoulli without adding more water to the equation. A kindo of compressed air system plunger or something.

    I don't want to sound militantly pro-plunger here, but give the plunger it's due. ;)

  2. Plungers are a fine instrument of applied mechanical force, to dislodge a hydraulic blockage, but I abhor having to clean them. After all, look at what it just plunged, and then store it behind the tank, or elsewhere, nasty? Ew. I'd rather not.

    And yes, I could increase the toilet tank capacity again, and use copious amounts of water on a daily basis, but I've only had to employ the Bernoulli principle 3 times in the last month or so - saving 60 to 100 extra gallons, and using perhaps 2 extra.

    Using compressed air or a raised tank would be fine for new construction, or where cost is no object, but when I'm already underwater by 50%, adding more improvements doesn't sound worth it.

    The use of "more water" by employing Bernoulli is not a daily occurrence. It is a rare phenomenon, chez nous.

  3. I am going to try the JoeP/Bernoulli method next time I get the chance.

  4. Honestly, in the 4 years since I posted this, each time I've tried it (1/2 a dozen) it's only worked about 1/2 the time. A MUCH BETTER solution is to buy the new smooth-flow toilets that (in California at least) are free, once you fill out all the rebates from the city & the water company. We bought one a few months ago, and it is flushing like a champ, no issues. Much less water, smooth surfaces inside the bowl and tubes, better construction and flow with less turns and restrictions. Highly recommended.


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