Lean Manufacturing

The Water Spider: What’s in a Name?

By Jon Miller Updated on May 29th, 2020

Lean Water SpiderOne of the things that keeps Lean manufacturing from being boring to the amateur linguist is the many odd-sounding words that make up the Lean lexicon.

And don’t even get me started on the acronyms!

What does a water spider have to do with lean?

There is this thing called the Water Spider. The Water Spider position is often confused with a simple material handler, or an entry level “go fetch” person. Far from it, the Water Spider needs to be thoroughly familiar with the materials, tools and methods of the process they are supporting. My teachers used to say the Water Spider role was a “right of passage” to becoming a supervisor. The Water Spider is an honored and critical role in making continuous flow and a smoothly functioning Lean system a reality.

Why the name Water Spider?

But what’s in a name? Why Water Spider? People often think this word comes from the insect that skims the surface of the water (water strider), but technically this is not correct. The water spider is the beetle that moves about inside the water, not on the surface. What makes this confusing is that the word “mizusumashi” in Japanese at times refers to both.
A good way to remember this is that while the water beetle dives into the water (dives into the process, gets close the the cell, even goes into the cell to do occasional relief work for operators), the water strider skims across the surface and does not go under the water (close to the process). The Water Spider in Lean manufacturing must be intimate with the process or cell they support, not just a pick-up-and-drop-off material handler.

Why is this important?

Who cares? Is this distinction important? Why are we even talking about beetles?

The similarity between the Water Spider (the person who moves about the factory or assembly line) and water beetle (swims under the water) was explained to me as how they move in the water or move about the factory. This explanation by itself might lead to the misunderstanding that the Water Spider is a typical material handler.

But here’s another theory. As I stated earlier, water spider is “mizusumashi” in Japanese. This is written phonetically as みずすまし or in kanji script as 水澄まし. The word literally means “make water cleaner” or “purify water”. I don’t know if this little beetle actually cleans the water or not. You would have to ask an entomologist. The water beetle does have little broom-like fibers on its rear legs, so perhaps that’s how it “cleans the water”. Or perhaps it was noticed that water spiders only lived in the clear water so they were given credit for making it clean.

If we suppose that the water spider (beetle) makes the water clean or keeps it clean, the water spider (human) also keeps the flow in the factory or in the flow line clean and smooth by taking on the occasional tasks (tasks that do not happen every cycle, such as material replenishment or making shipping containers). A clear process flow and defined work sequence (clear flowing water) is also a requirement for designing the workload of the Water Spider position.

Mike Wroblewski at the “Got Boondoggle?” blog wrote a great entry a while ago about his personal experience doing the work, and doing kaizen of the Water Spider job. Check it out.
The Water Spider role is very important and there is a lot more that could be said about the Water Spider in Lean manufacturing, but perhaps another day.

What’s your water spider experience?

Have you ever been in the water spider role, or are you currently serving in that role?  Let us know about your experience in the comments.

  1. emanon

    January 25, 2007 - 11:50 am

    You’re so about standard work but what is this terminology. It’s not standard. I went to Google and entered water spider alert your sight is the only sight with info on this term. Since this word is not standard terminology, perhaps you should ensure that the people receiving standard work procedures containing this term know the definition. I thought our plant was infested. Is this term completely proprietary to KAISEN?

  2. Jon Miller

    January 25, 2007 - 5:01 pm

    It is standard. Just not as well known as some other standard terms.
    If you want to find other references to “water spider” as used in the Toyota Production Sytem, Lean and kaizen, enter water+spider+lean in the Google search field.
    Do not use Google Alerts, this only gives you news or newly indexed pages.

  3. Ernesto Jorge

    May 18, 2007 - 11:09 am

    There is another native English-speaker that also speaks Japanese, whose name is Fred Harriman.
    He has a site on Kaizen where says that “water SPIDER” should be more properly called “water STRIDER”.
    But it do resembles a spider, not a beetle.
    I love both, Jon and Fred, for bridging the language gap in these issues. Perhaps they are anecdotic, but doubtless interesting.

  4. Jon Miller

    May 18, 2007 - 12:39 pm

    I’ve met Fred. He’s a good guy.
    I still hold that the water spider is a beetle that swims in the water, rather than on the water like the strider.
    If there are any entomologists reading, they can resolve this debate.

  5. Frank M Stroscio

    June 14, 2007 - 7:33 pm

    Can you explain how Pitch is calculated and used for water spider function?

  6. Jon

    June 15, 2007 - 7:30 am

    Hi Frank,
    The short answer is that pitch is a multiple of takt time, often tied to the pack out quantity, but basically any round number multiple that allows for a set interval of work to be performed by the water spider in synch with the paced production line.
    For example, if a product is produced every 90 seconds (takt time) and the container holds twenty units, the pitch increment would be 1,800 seconds or 30 minutes minutes.
    The water spider would make their round to that point every 30 minutes to pick up finished parts and move them to the next process. They would also drop off materials needed or perform other tasks to fulfill needs of that process, based on consumption of parts over the 30 minute pitch.
    It gets more complex when you are delivery materials to the line that come in non-standard packaging (returnable plastic containers from local suppliers with one quantity standard, cardboard boxes from overseas suppliers with a different quantity) since these will generally not have the same common denominator. I have been a situation where there is not enough space on the line to store large parts and the water spider needed to adjust the pitch to deliver parts every 2/3rd full pack out quantity, and we ended up having 2 water spiders for 3 lines.
    Also, when you combine material pick up and drop off into one cycle, you have to determine pitch based on what the standard work of the operator will be based on desired storage quantity and space on the line, and so forth.

  7. Ricardo Petra Abba

    December 6, 2007 - 5:49 pm

    Cummins also uses the term water spider in their lean manufacturing.

  8. Onni

    December 21, 2009 - 3:23 am

    I am a little confused. What kind of task the waterspider should do in addition to the material handling? Some examples ?

  9. Jon Miller

    December 21, 2009 - 5:22 pm

    Hi Onni
    Thanks for your question. The job of the water spider is typically focused on material replenishment but can include other brief bits of occasional work. Mainly this includes filling in for workers who need to leave the line for short periods and assisting during changeovers that require several people to coordinate their work on different areas of the machine. They key is to keep the main line running smoothly.
    The team leader or line leader should have enough time to address more time-intensive support actions such as training or andon response.

  10. Onni

    February 26, 2010 - 12:08 am

    Thanks Mr. miller
    I am trying to focus our waterspiders to do only the material replenishment and to cut out everything else. Of course there is also the evacuation and other things like that. In our case the water spider is really busy doing the replenishment and there is no time to do any filling for the operators. I can’t see the point in any filling for the operators. What I mean is that the really important material providing work interrupts too much if the WS does stuff like that. So it doesn’t fit my picture where I try to kill all the red time. Don’t get me wrong I am just trying to understand the idea in this thing and possibly get a new points of view.

  11. emily

    May 16, 2010 - 9:32 am

    what is the water spiders defense mechanism???

  12. Rajan Bhagwat

    February 4, 2011 - 1:52 am

    What I learned about ws is that they also keep an eye on the processes & report on any delays or disruptions if the material has not been used up that way bringing in attention to clearing the blockages & keeping the flow going. Any addition to this ?

  13. Joe

    February 7, 2011 - 2:24 pm

    Hello it’s WS part of waste? if we add more operators our product price go higher so the WS it’s necessary?

  14. Cesar

    November 5, 2014 - 8:24 am

    I started to use this term and incharged one person in a pilot Lean Line, and is working wonderfully.
    I have increased productivity up to 131% so far.
    It is really great.
    I encorage all of the Lean practcioners to give it a try.

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