Here’s an analogy I used with my leadership team (as well as with reps) to better explain how a call center operates.

It’s the Bathtub Analogy!

I’ve employed its use many times & even had managers who worked for me use it with their people.

* * * * * For those who’ve never worked in a call center, as well as those of you who have but never really understood the various principles “behind the scenes”, you’ll find this story informative.

People who are not thoroughly familiar with how a telephone Customer Service runs…and runs PROPERLY…will not understand, nor appreciate, just how very difficult it is to walk that proverbial line between “efficiency” & “effectiveness”!

If your callers are normally waiting “too long” before being able to speak with a representative (let’s say, more than 20% of them are waiting more than 20-30 seconds or hanging up), then you are NOT EFFECTIVE! You’ve failed to provide your customers with the proper level of service from a timeliness perspective!

Yes, granted, not nearly as important as eventually “doing the right thing for them”, but still important…especially in the eyes of upper management (“If it moves, measure it!”)!

And if you’ve ever been on hold yourself, you know just how very annoying it can be!!!

And then, on the other hand, if MORE than, let’s say, 84%-85% of your callers are being answered within 20-30 secs, then you are NOT BEING EFFICIENT!!!

Unless you’re handling 9-1-1 calls or a suicide hotline (or, in certain rare instances, a sales unit), you cannot afford to “always or almost always” answer your calls so quickly!

? ? ? ? ?

“Exactly what types of meds are you taking, Mike? We’re doing really great answering our calls so quickly & now you’re saying that we suck???”

Er, yes, from an efficiency perspective!

“Queuing theory” & the science of properly staffing your unit – – BY 15-MINUTE INTERVALS, not days, weeks, months or years! – – requires that you have X number of reps SITTING AROUND, DOING NOTHING, JUST WAITING FOR A CALL at different points in times.

There are actually mathematical equations (“Erlang C tables”) that will tell you exactly how many people you need in that 15-min interval, depending how how many calls you’ll receive (PLUS those already waiting in queue), the average length of these calls, & the “Service Level” you want to provide (“what % of callers will be answered in X seconds”).

(God bless Agner Krarup Erlang, a Danish mathematician, statistician & engineer who invented “traffic engineering” & “queuing theory”…back in the 1910s!!!)

And all of this depends on how well you’ve forecasted your anticipated volume…exactly when they’ll be arriving…how long the conversations will last…how well your people follow their schedules…how focused they are on handling calls (vs. doing paperwork or God forbid 😱😱😱, taking an unscheduled break or goofing off…they are people, not robots, and should ALWAYS be treated as such!)…assuming there are no systems issues, etc…

I’ve run many different organizations in my time and a call center is INFINITELY MORE DIFFICULT & SO MUCH MORE STRESSFUL than any other team or area that I’ve led!

It all boils down to this…

In every other area/business or whatever, you must always do a great job.


But in a call center, you must always do a great job…but also do it RIGHT NOW!!!

And the RIGHT NOW extends throughout the entire day! You must do it RIGHT NOW, before you do anything else!

Your people are governed by their schedule. Just can’t take a break or leave for lunch whenever they’d like.

And on top of all of this…

THINGS WILL CHANGE MID-STREAM FROM WHAT YOU ORIGINALLY FORECASTED…and then, you must react & correct your course.

RIGHT NOW! * * * * *

Back to our original story…

The bathtub analogy goes something like this…

The bathtub is the call center.

The water represents the incoming calls.

Sometimes, it comes through the faucet at incredibly high speeds (heavy volume periods), while other times, it’s more of a steady, “manageable” flow. There are certain periods when it’ll only drip out (graveyard shift) or maybe, nothing flows at all (when the center is closed or everything has crashed).

While the water fills, and remains in, the tub, that represents the “calls in queue”.

And the average time it takes the water to get from the faucet & out through the drain is the “timeliness indicator or waiting time”. This can expressed as “ASA/Average Speed of Answer” (aggregate waiting time for all calls / total # of calls”) or as “Service Level” (the % of calls that are answered by agents with X seconds of waiting).

Call centers have traditionally used both methods (one or the other) to track & measure their timeliness performance.

Personally, I favor “Service Level” as it’s much more customer-centric.

This many customers called me & I had this % of them “happy” or “satisfied” with how quickly I answered the phone.

“ASA/Average Speed of Answer”, on the other hand, can sometimes be misleading when you’ve had many calls that have waited an extremely long time. Averages themselves can often provide a distorted sense of what really happened…kinda like the person with his head in the freezer & his feet in the oven.

On average, he’s very, very comfortable!


The higher the level of water in the tub, the greater number of calls waiting in queue.

How long the water remains in the tub is really the result of 3 different factors…

1. How much water is already in the tub (calls already in queue),
2. How fast more water is coming in through the faucet or faucets (call arrival rate & call volume),
3. How fast water is leaving through the drain at the bottom (the collective ability of the workforce to handle new calls).

If the reps are all already busy on a call (or not available to accept a new call), it may be somewhat slow depending on the # of reps & how long the calls are lasting. As more & more agents become available to receive a new call (or are already available), the faster the group will lessen the number of calls in queue.

Ah, the drain!

Again, the drains represents the collective ability of the group to take on new incoming calls.

But many things affect the drain & its ability to have calls easily flow through it.

Sometimes, it can become considerably blocked.

But more often than not, there’s the “hair” factor to consider!

When reps are absent or on approved time off, that’s more hair in the drain. Your ability to handle calls in a timely manner is negatively impacted.

However, if you’ve planned & forecasted properly, you’ve already anticipated this & have made the necessary adjustments in staffing projections to handle the situation.

“Reps who don’t follow the schedule or return late from lunch/breaks” also represent “hair in the drain”.

“Staff meetings, training sessions, one-on-one reviews, etc.” are also examples of still more hair.

However, by working closely with your “Control Desk”, your Planning & Scheduling coordinators can appropriately plan for these occurrences & make sure they’re properly placed in the schedule so that the center has sufficient resources. No call center has the exact same volume throughout every 15-minute period of the day, week, month or year.

Capacity Planning is able to figure out (based on forecasted volumes & call arrival patterns) how many reps are needed for every 15-min segment to meet an acceptable Service Level, then plan “off-phone activities” (time off, lunch, breaks, meetings, training, etc.) around that.

Nowadays, the Erlang C table intelligence & functionality is built into all WFM/WorkForce Management scheduling programs. You enter all the required variables & it’ll spit out a comprehensive daily schedule for every person in your organization.

So what else affects the drain’s ability to offload that water?

If the system is “slow”, that will cause calls to last longer & effectively add more hair to the drain.

So will newer or inexperienced reps on the floor as they generally have longer “AHT/Average Handle Time”, that is, from when the calls arrives in the rep’s headset until when he’s ready to take another call.

Good WFM people will adjust their talk-time assumptions, based on the “experience & expertise mix” of the reps, for every 16-min period of the day (as appropriate).

One component of AHT is “after-call work”…stuff the rep does after the customer hangs up, but before they tell the system that they’re ready for the next call.

Sometimes, they’re completing a form…sometimes, they’re performing a task on, or following up on something from, a different call earlier in the day…and still other times, they’re simply just not being productive at all! Yeah, it happens.

And in a call center, it’s not only important what you do & how you do it, but when you’re doing it!

When there’s a queue, especially a large one, reps still need to be focusing on the call that they’re handling right now. That’s a given!

Do NOT rush through the call or omit anything you would normally do for these customers. The customer ALWAYS deserves your best effort…regardless of what’s going on you…and he doesn’t give a crap how many other callers may be waiting.

Nor should the rep (worry about the queue or if the sky is falling)!

But when the rep is finished servicing their customer completely, they need to “make themselves available “ to receive another call.

Managing & controlling after-call work is a MAJOR factor in maximizing a call center’s ability to operate effectively & efficiently.

“Excessive” after-call work is more hair in the drain.

Just like when when reps make themselves “unavailable”, they’re not on a call, not waiting for one, not doing follow-up related to the call they just handled.

They could be on lunch or a break or another scheduled/authorized time away from the phones…or maybe they’re not.

More hair in the drain.

When reps return from lunch or a break or anything else & “go available”, that’s like pulling some hair out of the drain.

Yeah, I know…YEEECCCH!, but it’s a good thing for the call center!

At times, calls can wait for a significant time in queue. The customer gets frustrated with the waiting time & hangs up.

Same for water sitting in the tub…that results in some evaporation! Abandoned calls.

Evaporation in a call center is not a good thing as it’s normally specifically tracked & should have a negative impact on Service Level, not to mention customer satisfaction.

(Yes, abandoned calls actually help reduce the size of the queue, but…)

They’ll be times when the water (incoming calls) is coming out of the faucet just as you expected (forecasted call volume & arrival rates).

But if that drain is clogged up (due to higher-than-forecasted absenteeism, Systems issues or rep behavior causing higher-than-usual Average Handle Times, Managers holding meetings without clearing it first with the Control Desk/Capacity Planning coordinators, etc.), then your ability to let that water out through the drain is compromised.

Waiting times will increase as will the # of calls in queue (the level of water in the tub).

And the longer the water sits, the more likely that it will eventually evaporate (Abandoned Calls increase).

The trick to running a super-efficient & effective call center is NOT to always have an empty tub (or even try to)


If you do, then you’re being inefficient. While you may have a great Service Level & few Abandoned Calls, you’re way over-staffed. You have too many reps just sitting there, waiting for a call.

Doing nothing.

Waiting for a call is 100% unproductive. Yet, the “right amount” of “idle reps” is necessary to achieve your timeliness goals

The challenge (trick?) is to try & maintain a “minimal level” of water in the tub.

Not enough to cause customer dissatisfaction (waiting too long in the tub to get through the drain), but enough to provide a steady & expected flow of water into the drain.

It’s vitally important to forecast accurately…for every 15-minute period of the day. How many calls do we expect & when do we expect them?

It’s vitally important for the workforce to follow the schedule as best as possible (“good adherence”). Never cut a conversation short because you hafta go to lunch or on a break, but try your very best to follow the schedule.

It’s vitally important to have good attendance. Yes, you can accurately forecast for poor attendance & still have great Service Level results, but you’ll be throwing away money. And unscheduled absences can cause havoc to even the best-prepared schedule. (You can’t just have your people work some OT to catch up on what they weren’t able to get to during their normal shift!)

And it’s vitally important to have effective & open communications channels betweens the call center teams & the Control Desk.

Early notification of systems issues, requests for time off the phones (meetings, training, reviews, etc.), letting the teams know about “excess availability” (too many reps sitting around waiting for calls…you can’t do better than 100%!) so Managers can hold meetings, call calibration sessions, training, etc….all important endeavors for a well-balanced call center!

Your reps can’t be on the phones 100% of the time so make sure you’re maintaining a healthy balance between providing good timeliness performance for your customers & a good work environment for your people!

Well, that’s about it. You’re more than welcome to use my bathtub analogy…especially since I forgot to copyright it!

The more your people understand how the call center works conceptually, the better they’ll know how the various things that go on during the day fit into the bigger picture.

It’s the same way when they’re servicing their customers…if they truly understand how a particular product or service works (especially if they’ve used it before themselves), the better equipped they’ll be to solve any problems & actually have an intelligent conversation with the caller (instead of simply reciting rules).

The more your people understand the bigger picture & how everything fits/works together…

…phone calls, visits to the branches, on-line banking, ATMs, mobile banking, writing checks vs. paying electronically, direct deposit, auto debits, deposit delays vs. expedited availability, using your phone to make deposits & a hundred other things…

…the better they’ll be able to educate the customers & improve their experience with your institution!

Good luck!

And if you fell asleep after the 34th paragraph, there will be a test…

…and I’ll be sitting in the back of the classroom!!! 🤪


As always, thanks so much for listening!

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