Low Flow Toilets Equals No-Flow Sewers In San Francisco

If you’re an environmentalist, particularly a San Francisco version of that creature (one of the most virulent of the breed), it must have come as quite a shock for you to learn that your muck stinks just as bad as a Rush Limbaugh fan’s output. The stench from the sewers in that earth-loving city has become overwhelming, “especially during the dry summer months.”

Why? The low-flow toilets insisted upon (by force of law) by enlightened legislators are not saving the San Francisco environment as the science said they would. According to SF Gate, the near water-free commodes have forced city engineers to mix in 27 million pounds of “highly concentrated sodium hypochlorite” with the sewage “before it’s dumped into the bay.”

San Francisco SewerAgain, why? The ineludible Doctrine of Unintended Consequences.

Now, it wasn’t that long ago that folks like writer Alexandra Marks thought that she could “become a better human being” by teaching us to “flush with clean consciences.” Low-flow toilets, as the science said and as the chant went, would save the environment (from what or for whom is never told).

The motive was pure, but the problem was that most low-flow toilets were crappy. Marks quoted Dave Berry:

They work fine for one type of bodily function, which, in the interest of decency, I will refer to here only by the euphemistic term ‘No. 1.’ But many of the new toilets do a very poor job of handling “acts of Congress,” if you get my drift.

Many low-flow toilets had to be flushed at least twice for acts of Congress, thus using as much water as the old-style toilets they replaced. But if governments are good at anything, it is moving muck, and they had soon passed enough laws and granted enough grants that new breeds of low-flow toilets performed their functions admirably.

Indeed, it was learned that it would even be possible, by purely mechanical means, of removing acts of Congress from toilets and shoving them into the sewage system using almost no water whatsoever! What a boon for the environment!

Alas, this dream merely proved that activists could only see as far as the bottom of their bowls. The Doctrine of Unintended Consequences struck with force when it was discovered that the water which relocated the acts of Congress from toilets was also necessary to shift the Congressional output through the sewer system! Who knew!

Instead of a laminar movement of muck found with the old toilets, low-flow toilets caused stagnation. The acts of Congress left the homes of the benevolent, but when they plopped dry into the sewer, there they sat, festering and bubbling and turning into a giant petri dish. And they stank.

And still stink, hence the plan for dumpling concentrated bleach into the sewers to make up for the lost water. Some of the bleach must also be used to kill critters in the drinking water, too.

In what must be a fascinating sociological experiment, the very forces of benevolence which created the demand for low-flow toilets is now pressuring politicians to eschew chemicals. “Don’t Bleach Our Bay!” is the new environmentalist cry. Activists are claiming that the bleach will cause an “environmental disaster” and is thus not “planet-friendly.” They suggest—I kid you not—using Oxyclean, or it’s sewer equivalent, to scrub clean their effluvia.

This being a world in which politicians are driven by fear more than by conviction, those who throw the biggest tantrums usually get their way. Consequences don’t matter: what really does is how much you care. And who cares as much as an activist? Thus how long until San Francisco visitors are advised not to drink the water?


  1. John B

    Similar propaganda drive for London, but no legislation, to put objects such as house bricks in the cisterns to reduce water use.

    However additional problem for London’s Victorian brick and mortar sewers, if the mortar dries out, it contracts, crumbles and the sewers collapse.

    Meanwhile water is 100% recyclable so what exactly is being “saved”? Its precessing? So what.

  2. Pat Moffitt

    That Stink is hydrogen sulfide– which volatilizes within the sewer lines and is acted upon by bacteria forming sulfuric acid. This acid then drip down the walls of the sewer eventually causing them to collapse.

  3. Mike B


    Too bad Billy Mays isn’t still around to shill for it.

    I hear Charlie Sheen is looking for work….

  4. The whole idea was a plot by Napa Valley vineyard interests to convince tourists to skip drinking the water in favor of more “user friendly” local liquid outputs. Besides, they are “organic”.

    Mike B. I think Charlie isn’t so much looking for work, but “validation”. As if.

  5. The other thing that struck me as odd is why they did not use sea water to flush the mains? Too far from the ocean? Should be a lot easier to neutralize afterward than bleach, but what do I know?

  6. DAV

    I think I’ll start stocking up on tomato seeds.

  7. Doug M

    Mostly this is a story of green hyperventilation with no real news. Bleach dumped into a storm drain in the summer months would find its way to a treatment plant before it hits the bay. Untreated runoff only flows to the bay after big storms.

    Low flush toilets have made the problem worse, but it isn’t new. San Francisco has had stinking storm drains for ages. We have a dry summer, and there is no rain water to flush out the storm drains. Many neighborhoods have groups of volunteers sniffing strom drains and recommending when one needs to be cleaned out. I can’t say for sure if this is the first time the city has approached the problem with bleach, but I would guess that it is not.

    On the politics of water — As California is effectively a desert, we have to dam large valleys to make our reservoirs. The rain falls in the north of the state, and we pump it into the central valley and the cities. Any water flushed down the toilet is less water for use elsewhere. 1.6 gallon toilets are California code and not just city code. Furthermore, Enviros want more water to flow down the rivers. When we have a dry year, the smelt rank higher than the farmers.

    Speed, the sea lions are back at the pier.

  8. GoneWithTheWind

    Something stinks with this story. All the water you use in the house goes down the same drain that #2 does. A typical household may send 200 gallons a day down the drain from non-toilet use and perhaps 4-5 gallons from going #2. So I fail to see how the small change in flow from toilets could cause this problem.

  9. Lynn Clark

    GoneWithTheWind said, “…and perhaps 4-5 gallons from going #2.”

    And how much from going #1? Low-flow toilets don’t just do the “low-flow” thing when you go #2. Sewer systems are designed based on assumptions of average water flows within them (among other considerations). Going from say, 3-4 gallons per flush, to 1.6 gpf has an effect on the average water flow in the system. And don’t forget about the effect of the other government mandate for low-flow faucets (I know, we’re all too stupid to know how much water to use). I routinely run the water in my kitchen sink for a lot longer than I used to before I replaced the old faucet with a new low-flow faucet, just to try to make sure all the stuff that goes into the garbage disposal makes it to the sewer pipe in the street instead of plugging up my plumbing.

  10. andy

    Putting bleach down has to be the worst idea ever. The sewers smell cos of the bacteria breaking down the poopoo. Kill them off and you have solid poopoo with nothing to break it down. Solid poopoo builds up and blocks your sewers. Which overflow and smell.

  11. DEEBEE

    Matt – can’t resist – that was MMM MMM MMM …

    GoneWithTheWind — check out laminar flow vs. stagnation. The instantaneous flow is more important than the daily flow. Once the Congressional output plunk down you can only hope to shave off the top layers with the remaining flow. Sorry TMI

  12. John Newcomb (Victoria, BC)

    While the only toilets one may install now are 6-litre variety, San Francisco is old enough city that there would be mostly older 13/22 litre toilets actually installed, so I’m skeptical that low-flow toilets that would be the most significant cause of stink, but I guess it is the one thing that appears to have been changing in past couple of decades so its the prime candidate for the cause. However, there may be other things happening too, such as climate change reducing further SF’s rainfall to virtually nothing in summer months, and not so much in winter months? As well, the issues of inflow and infiltration to sewage pipes, while usually high in older systems, may have been fixed recently. I&I means less sewage water to treat, but would also reduce in-pipe flow. At same time, if pipes are an aging problem, issue of exfiltration – losing sewage water out of pipes and into the ground – might be related issue?

  13. JH

    Ewww… thanks to the olfactory adaptation, people can get used to the stench.

    Is this post supposed to be a joke?

    Having lived in a big city before, I have always thought that sewage problems are an inevitable consequence (and cost) of population growth.

  14. Can’t you hear Tony Bennett crooning ” I smelt a fart in San Franciscoooo”?

  15. Pat Moffitt

    The real story here is to see if any warnings and cautions from the engineers were ignored. This problem should not have surprised the engineers as the potential is rather easy to calculate from the sewer design.

    JH and Gone with the Wind- The higher the flow the less the problem as hydrogen sulfide can only be evolved in an oxygen free environment. (So increasing population “solves” the hydrogen sulfide issue by reducing residence time) Low flow means low velocity allowing the solids to drop out in the sewer lines exacerbating the problem. The low flow toilets most likely add to the low flow shower heads and other water conservation devices.

  16. I am reminded of this song performed by Art Carny:
    Song of the Sewer
    Song of the Sewer
    I work in the sewer, it’s a very hard job,
    You know they won’t hire just any old slob,
    You don’t have to wear a tie or a coat,
    You just have to know how to float.

    We sing the song of the sewer,
    Of the sewer we sing this song,
    Together we stand with shovel in hand
    To keep things rolling along.

  17. Eric Anderson

    John Newcomb: “such as climate change reducing further SF’s rainfall to virtually nothing in summer months, and not so much in winter months.”

    Do you have any statistics to back that up? I can tell you categorically that a few miles to the south (in San Jose) there hasn’t been any kind of meaningful trend over the last 100 years.

  18. JH

    Mr. Pat Moffitt,

    I just can’t imagine how a toilet flush with a lovely swirl (does yours swirl clockwise or counterclock-wise?) can have effects on the flow of the CITY sewer system? Powerful it must be.

  19. Pat Moffitt

    JH- given you “can’t imagine” makes it impossible to explain subcritical flow.

  20. JH

    Mr. Pat Moffitt,

    JH- given you “can’t imagine” makes it impossible to explain subcritical flow.

    Oh come on, this is bull… (I would say this in front of you also!)

    I don’t need your explanations of sub or super-critical flow. I need some explanations on how a toilet flush or the velocity of it affects the flow of the waste in the CITY (not residential) pipes.

    I am inclined to agree with Newcomb’s assessment that the sewage problems have more to do with the waste-carrying ability with a given volume water, and population growth has caused an increase in the amount of waste in those aging pipes. Well, I know this is not as simple as I think.

  21. Jeanjacque

    If the low-flow toilet is required to be flushed twice to move “acts of Congress,” would the water supply to sewers not be adequate?

  22. harrywr2

    GoneWithTheWind says:
    2 March 2011 at 1:17 pm

    “A typical household may send 200 gallons a day down the drain from non-toilet use and perhaps 4-5 gallons from going #2. ”

    I had the unfortunate experience of having to fix this problem at my wifes rental property that she rented to an ‘environmentally conscious person’.

    Ms. Environmentally conscious would put rice down the sink drain washing it down with only enough water to clear sink trap. Said rice made it all the way to the houses 4 inch waste pipe.
    Ms. Environmentally conscious would then go to bed and use no further water for the night. Said rice had plenty of time to dry and harden.

    In the space of 6 weeks, she managed to clog a 4″ drain pipe with rice. Just not enough water to keep the rice ‘moving along’.

  23. Pat Moffitt

    JH- do I think this is all the result of just low flow toilets – no- but there are any number of flow reduction intiatives at work- shower heads etc. Sewers are designed for Both a minimum and maximum flow. Minimum flow safeguards are needed to maintain a velocity sufficient to keep solids from settling in the pipe. When flows drops, velocity drops, solids deposition increases, retention time increases causing increased oxygen demand and anoxic conditions. The bacterial slime on the wetted perimeter of the pipe under anoxic conditions takes in SO4 from the wastewater and converts it to hydrogen sulfide which is emitted as a gas. Another set of bacteria that live on the crown of the pipe “eat” the H2S forming sulfuric acid which drips down the walls of the cement pipe causing it to crumble and the lines to eventually collapse. The gas is also more toxic than cyanide and is a leading cause of death for workers. (A reason why we evolved an ability to smell H2S at extremely low levels and find it so repugnant) Hydrogen sulfide is a low flow problem.

    It why I said I’m sure their engineers warned at some point against pushing too many water restriction devices.

  24. Parabellum

    Former plumber here. Here’s how I used to explain low-flow toilets to customers. Low-flow toilets have the same size tank (usually) as a standard toilet. A low flow toilet simply closes the flush valve (flapper) sooner than a standard toilet. The tank does not completely empty with a standard press of the lever, thereby ‘saving’ water.

    How to make a low-flow toilet function efficiently:

    When flushing #1, press the lever down and release it immediately.
    When flushing #2, press the lever down and hold it down until the tank empties completely.

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