Low Flow meets Physical Chemistry

OK, so I’d been on the road a few days. Time to get the ‘road grime’ off, so I hit the shower for a ‘quick wash’.

I’d been doing “Efficiency Showers” in Orlando as first thing in the morning, time is dear. Similarly, after a load of ‘Push’ on the road, you just want an ‘Efficiency Shower’ to get the dirt off as you REALLY just want sleep…
So I took a long shower.

The Low Flow Problem

In Orlando, I’d gotten used to the ‘regular flow’ (or ‘high flow’) showers. Nice. Fast. Without the slow adjustment of showers at progressively more restrictive places as I crossed the country (being I was ‘all drive, no stop’) I had a ‘reentry shock’ here in Kalifornia. The Low Flow Shower Head, mandated by local laws.

So I soaped up, and began to rinse. And rinse. And rinse.

Plenty of time to contemplate “Why?”. Why was it taking so long?

I think it is the reality of physical chemistry.

A Body of Soap

A person has a fixed surface area. It has a fixed amount of dirt and oils on it for any given shower event. This requires a fixed (though you can use excess) amount of soap and water to get the hydrophobic ends of the soap molecules dissolved into the oil film layer. The lower the flow rate, the longer it takes to get enough soap and water on. I’d not noticed the added time from the low flow on the ‘soap up’ all that much, probably as it’s the first step and fairly fast any way. You only need enough water to dissolve some soap off the bar and spread it around. A little slower, but even 1 gallon is enough, so we’re in the fractional minutes range for any flow rate over 1 gpm.


Rinsing is another matter. Now you must make an emulsion out of that oil/soap film and disperse it into an excess of water. That takes more water and a fair amount of turbulence. The formation of an emulsion takes the hydrophilic ends of the soap and gets them entangled in a small water droplet, that then physically pulls the soap and the oil film attached to the other end off of your skin. That takes more pressure, flow, time, and water.

I rinsed. And rinsed. And rinsed.

Eventually I was clean. But the length of time needed was far longer than in the high flow showers I’d been taking.

Now I’ve not had time to ‘do the math’. There may yet be some actual ‘water savings’ in the process. BUT… It is at the cost of human time. My time is far more valuable than a gallon or three of water. I also have to wonder just how much the low flow also means ‘less clean’. I do feel like I never did quite get all the soap film off. Like I gave up too soon.

In Conclusion

I’m fairly sure that the Low Flow idea is sold based on a direct volume / time comparison. It needs a “volume to get the same amount of clean” comparison instead; and an adjustment for “$ worth of labor / time wasted” per cleaning. Basically, the math of the present justification is wrong.

A simple “what do I feel about it” says that the bias in the Low Flow mandate in California is way too far the wrong way. Next time I’m out of state I think I’m going to pick up a Florida Shower Head ( or maybe a Nevada if they are normal sized…)

In the end, I think that physical chemistry mandates that at some point you end up spending more time for the same benefit, but not saving any water. IMHO, that point is at about 2 x the mandated water flow rate in California.

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About E.M.Smith

A technical managerial sort interested in things from Stonehenge to computer science. My present "hot buttons' are the mythology of Climate Change and ancient metrology; but things change...
This entry was posted in Political Current Events, Science Bits and tagged , , . Bookmark the permalink.

10 Responses to Low Flow meets Physical Chemistry

  1. Scott Finegan says:

    The hardness, or softness of the water has a larger effect on soap effectiveness and dirt removal, than water flow. It takes far less hard water to wash the soap and dirt down the drain. Change to cold, hard water to accelerate the process even more :)

  2. Judy F. says:

    In the “just the same but different” category, I have a problem with my dishwasher. With my old dishwasher, I could use 1/2 the recommended soap, skip the soak cycle and in 45 minutes I would have clean dishes. Now I have an Energy Star dishwasher, that takes over 90 minutes to run the cycle and I frequently have to wash some of the dishes twice. To top it off, I have to use the strongest kind of detergent to get the dishes any kind of clean. The water saving feature runs on a timer, instead of a float, so if you have low water pressure, you don’t get enough water in the dishwasher. Since the cycle takes so long to run, the incoming hot water cools off in the pipes, so then the heating element turns on to heat the water in the dishwasher. How in the world it deserves an Energy Star rating is beyond me- It runs twice as long, requires a heating element for the water, and needs extra strong soap. I guess it does save a gallon or two of water, although that savings is negated when you have to scrub any residue off your dishes before you put them in the dishwasher. Sigh. I love the law of unintended consequences!

  3. H.R. says:

    I say, “Get the government the heck out of our bathrooms!!!!”

    Take your pick: a low flow toilet that needs flushed 2-3 times or a good ol’ fashioned loo that does the job with one mighty whoosh.

    If I am elected, I solemnly promise that I shall return the freedom of the bathroom to the people of this great and glorious land.

    Thank you very much.

  4. R. Shearer says:

    A Dremel tool with appropriately sized bit can solve that low flow.

  5. Lynn Clark says:

    You really notice this when you remodel your kitchen and replace a 20+-year old faucet with a modern low-flow faucet (they’re all low-flow now; see below). Now it takes minutes for the hot water to make the trek from the hot water heater to the faucet. The same amount of water runs while I’m waiting for the hot water to get there, so where’s the benefit? Then, when I send left-overs and unusable parts of lettuce heads, etc., down the disposal, I have to run the water a heckuva lot longer to (hopefully) insure it all makes it to the sewer connection in the street instead of blocking the plumbing.

    I guess we can all thank (willful) misinterpretation of the commerce clause for this situation. When I first installed the faucet I was so dissatisfied with the low flow that I went to the Peerless (manufacturer of the faucet) website to see if there was any way to increase the flow. I about fell off my chair laughing when I read their response to a FAQ about this:

    Q: Why does my new faucet have reduced flow? My old faucet had plenty of volume.

    A: Well, here’s the thing. Every faucet produced since 1994 has been restricted to conserve water (per EPA code mandates). Older faucets were produced before those restrictions went into effect.

    I’m not making this up. Here’s the URL: http://www.peerlessfaucet.com/customer-support/faq/water+pressure/index.html

    If the above URL doesn’t make it past the wordpress filters, just go to peerlessfaucet dot com, then click on Customer Support -> FAQ -> Water Pressure.

    I just love it when politicians — mostly liberal, progressive idiots — think the rest of us are too stupid to not turn on the faucet full-blast when it’s not necessary.

  6. dearieme says:

    In our bathroom, in a dry part of England, we have a “Power Shower”, a pump-assisted device that really blasts the water out. It’s very hard, artesian water.

    Both our loos offer us the choice of big or small flush.

    We pay for our decisions because our water supply is metered.

  7. j ferguson says:

    Let me know when you run for office so I can move there and vote for you.

    I often wonder how someone with a program like yours would do. It might be fun to compile a list of the newly discovered morality choices made for us and inflicted by one law or another, compile the list into a program and then run on removing these obnoxious constraints.

    I don’t mind paying for water and the gas needed for the hotwater heater, but i really resent someone telling me at what rate I can use them at.

    Living on a boat sometimes requires that water be hauled in four 5 gallon plastic jugs and swung over the gunwhales to be poured into 150 gallon tank – by me.

    I have a very enthusiastic pump and have removed the inhibitor from the hand shower nozzle. We take very effective showers using what is known as a “navy shower” this is where you get yourself wet, turn off the nozzle, lather up, turn on the nozzle and blast it off. then maybe a little rinse. heat is either by exchange with engine coolant, or an electric calrod powered by the generator.

    I drilled out the restricters in the shower heads in our last several homes. I always imagined being hauled into court for this infraction, demanding a jury trial and getting off because “No jury in the land would convict for something like that.” I was even able to imagine being carried out of the court room on the shoulders of the jury members.

    I’ll have to cut this off. I’m getting froth on the keyboard.

  8. Verity Jones says:

    Ah, now here’s something that can help: a pulse showerhead. http://pulseecoshower.com/Technical/tabid/767/language/en-US/Default.aspx They’re in some European hotel chains and you really wouldn’t notice you are having a ‘low flow’ shower.

    “Pulse Showers showering performance @ 9 litre per min equals a standard showerhead @ 19 litres per min.”

    We studied the rain

    “The experience of a comfortable shower is strongly tied to the quantity of water used. High water consumption however does not ensure an efficient shower. There is, however, a clear connection between output and comfort. An important criteria for the Pulse Shower therefore, was to be able to harness the natural properties and physics of water.

    There are many examples showing that research and technical innovation have actually gathered ideas from nature. Similarly, Pulse Shower studied the rain.

    At Multishower we noticed that in a real cloud-burst, the water come as large, juicy drops at very high speeds. This was what PulseShower wanted to emulate for it’s new concept in shower heads. As in a cloud-burst the showerhead wanted to have a water structure with high kinetic energy: K = ½ Mv2, that is, large drops at high speed. And as opposed to other conventional showers, PulseShower did not want the water to hang together.”

    And a cool demo video: http://iebsoftware.com/multishower/multishowervideo/index.html

  9. Pascvaks says:

    Our only hope is two new political parties in this country: the Deleatocrats and the Repealicans. Oh yes! And a new phrase in the Constitution that mandates that no representative or senator can have more than a 3rd grade education or serve more than 2 terms in either the house or the senate. The problem with presidents will need to wait until the 22nd Century.

  10. PaulID says:

    J. Ferguson
    What we need is for those with a similar mind economically to move together and start a new state and prove to these idiots that good policy can work H R can be the first governor and E M can be in charge of setting up economic policy.

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