[bryanjclark]

Except for one issue: it actually slows down the efficiency of the bathroom.

See, by splitting up washing and drying into two steps, you allow two people to be in the process of cleaning their hands at a time.

By bundling the two steps together, you reduce the amount of stuff in the bathroom, but you also reduce the efficiency of the bathroom.

This AirBlade Faucet is a great idea for low-usage bathrooms: less paper towels, less equipment to maintain, etc. For high-volume bathrooms, (airports, etc) this would actually be a step backwards to put these faucets in, if a goal of the bathroom is to be able to quickly serve a large group of people.

[oh_sigh]

Have you done the math on this? I have a feeling you're relying on a gut instinct and didn't actually simulate it. From my simulation, this new gadget will simply shift lines from the paper towel dispenser/on the wall air dryer to the sink itself. It will not at all reduce the efficiency of the bathroom, infact it will increase it

[ChuckMcM]

I chuckled because this same exchanged happened in my head when I read the article, my first thought was "Oh great, everyone stuck at the sink" followed by "Would they stay at the sink in practice?"

I've seen a couple of air-blade installations, and in those they have slowed things down because paper towel dispensers allow you to take a towel, step back, and dry your hands while another person gets a towel. Rolling towels (ones where the towel is on a continuous loop) have the same issue of one user at a time.

On the other hand ever every faucet was also a drying station you've basically upped the number of drying stations tremendously and that is a win for speed.

Side benefits of keeping water off the sink/floor are good.

I wonder if we'll ever see anyone taking this to the extreme of stalls with only water and air tools for washing up (Japanese style toilets for wiping, local air-taps for your hands).

[oh_sigh]

> I've seen a couple of air-blade installations, and in those they have slowed things down because paper towel dispensers allow you to take a towel, step back, and dry your hands while another person gets a towel.

I largely agree with your points, but I wanted to point out that most modern bathrooms(and certainly not bathrooms that may have this device deployed) don't have paper towel dispensers. So it isn't a question of paper towels vs this technology, but this technology vs the hot air fan, or the dyson air blade, or other similar non-dead-tree tech

[jpatokal]

Japanese bathrooms still have toilet paper dispensers, because even those probing little robot arm squirters can only clean so much. The usual protocol is thus to wipe with paper before you enjoy squirty fun time.

[stcredzero]

> Side benefits of keeping water off the sink/floor are good.

What's keeping the air from blowing droplets of water from the sink to my shirt or face?

[ChuckMcM]

Well if you've used one of their airblade systems you can see that they have a 'down shoot' sort of effect. I've never seen an air-tap so I don't know if they achieve the same result but I suspect that the water uses the same path as the air, and so blowing toward the sink would make the most sense. In that case a poor basin design could get you into trouble with water bouncing back I suppose.

[dhughes]

An AirBlade bidet, ouch!

[moe]

I don't know about your simulation, but over here in the real world it doesn't work that way.

Many people don't dry their hands at all in a public bath room (that's what god invented jazz hands[1] for).

By combining faucet and dryer you force these people into the same bottleneck as the hand-dryer users.

[1] http://www.youtube.com/watch?v=xuPSIbABYVU

[oh_sigh]

> I don't know about your simulation, but over here in the real world it doesn't work that way.

Wow, great point. You're obviously unbiased! You don't even know the details of the simulation, but you're confident that you really know what's up based on your presence in "the real world".

> Many people don't dry their hands at all in a public bath room

Yes, but they still wash their hands. Many people don't dry their hands because they have to use the hot air blowers, which they know are ineffective. If they see an effective device, some members of that group will choose to use it instead of jazz handing. But even discounting those people, the wash + dry combination still works out better for most cases I can devise. The only universe I have come up with where wash and then dry else where is better than washing and drying at the same station is if there are an equal number of paper towel dispensers as there are to sinks, which has never happened in a bathroom where the number of sinks > 2, as far as I know.

> By combining faucet and dryer you force these people into the same bottleneck as the hand-dryer users.

I wasn't arguing for optimizing any one special interest groups time spent in the bathroom, I was optimizing for the total network throughput of the bathroom.

[moe]

I was optimizing for the total network throughput of the bathroom.

But you didn't. You have serialized access to two resources that were previously independent.

Since a significant portion of users need only one of the two resources you have created a new point of contention. For access to the faucet not only do I have to wait for people washing their hands, now I also have to wait for people drying their hands.

[petsos]

Yes but one of the resources (the dryer) has increased significantly too. And since we are both using the word "significant" instead of any real numbers we can prove either point.

[stcredzero]

I call BS. It should only take 6-8 seconds for someone to grab 2 pieces of paper towel once they're at the dispenser. That means 2 towel dispensers should be a match for 5 sinks.

[incongruity]

It's actually worse because you take what were 2 parallel operations (washing your hands and drying them) and make them two serial operations, not able to be run in parallel.

[oh_sigh]

Yes, it does upset the balance slightly for people who want to wash their hands, but not dry them, and for people who want to dry their hands, but not get them wet.

Those are the only scenarios where your argument holds, however.

[incongruity]

No, not at all.

Simply put, you are moving from 2 independent operations to 2 mutually exclusive operations – meaning that 1 sink (in the Dyson case) can only service 1 user at a time vs 1 sink+1 dryer/towel dispenser which can, at a minimum, service 2 users at once (there's actually a much bigger set of time/path calculations that could go in to this, but the simple case is enough to make it clear that your thinking is confused on this.)

[incision]

>Except for one issue: it actually slows down the efficiency of the bathroom.

With one exception, every bathroom within my memory had the drier as a bottleneck, typically at a ratio of 3:1 or worse.

Having a drier per sink would actually improve the efficiency.

The one exception was a older building which had towel dispensers over each of 5 sinks. They eventually replaced them with a single dispenser on the wall at the end of the row. Problem was, towels would inevitably fall in the sink and cause a clog.

[tocomment]

That's only if you assume unlimited paper towel stations. In reality hand drying is the bottle neck. So if every sink has its own dedicated dryer it will speed things up.

[lttlrck]

"every sink has its own dedicated dryer"

Exactly. Sinks seem to always outnumber dryers by a wide margin.

[r00fus]

Don't ignore the folks who actually don't want to airdry their hands.

I soap, wash, shake and wipe my hands in my pockets as I walk out the door if I'm in a hurry.

[epo]

But you wouldn't get a queue for paper towels. People would grab 2 or 3 towels and move aside.

[tocomment]

Maybe but there's a bit of a shuffle getting around people who have grabbed towels. And there are always the people who stand by towels to dry because that's where the trash can is.

Actually, I guess separating the towel dispensers and trash cans in existing bathrooms would be a smart efficiency move since it would encourage people to grab a towel and keep moving.

[ricardobeat]

It says fourteen seconds. Washing your hands in the sink then walking over to the dryer/paper dispenser, pressing levers or waving your hands, easily takes 30s. Plus you'll never find a bathroom that has a dryer for each sink, so there are massive gains in parallelism :)

[rytis]

Not sure. Let's say a person spends 15 secs washing, and 15 secs drying. Combined it's still 30 secs. So if we have a long queue, does it really matter that two people are in the bathroom at any given time, or just one? The total processing time does not change.

Or am I missing something here?

[beala]

It actually does help, and the concept behind it is called pipelining [1].

Suppose there's a sink that washes and dries, and there are two people who want to use it. The second person will spend 30 seconds waiting, and 30 seconds washing/drying. So, 60 sec total.

If there's a sink and a separate dryer, the second person will spend 15 sec waiting, 15 sec washing, and 15 sec drying. So, 45 sec total. The second person gets a 15 seconds savings, because he can start washing as soon as the first person finishes washing, rather than having to "block" until the first person is done washing and drying.

[1] http://en.wikipedia.org/wiki/Pipeline_(computing)#Concept_an...

[pbhjpbhj]

But your pipeline stalls as you've people waiting to use the drier, those people block sinks, flow is reduced.

1 sink and 1 dryer: first person leaves after 30s, after 60s 3 people have been served.

2 sink and dryer combos: 2 people leaves after 30s, after 60s 4 people have been served.

I think the analog is that parallel processing is better than pipelining.

[cmsmith]

I think your assumption of equal time for each task is incorrect. Either because people don't dry their hands, or it doesn't take as long as washing.

Because typical bathrooms have 4 times as many sinks as they have hand driers, and I still see sink lines more often than drier lines.

[roc]

Only because "air drying" is a more acceptable option than "not washing". So a combined station would only slow things down inasmuch as people no longer skip drying.

In general (at least in the US) drying takes far longer than washing. Because most people wash quickly/poorly whereas driers are on timers and most are horrible.

And when your hands are still wet even after negotiating the unresponsive sensor and waiting an entire drying duration, it's understandable that many people would just as soon skip it.

[rytis]

OK, but still that doesn't change the equation. 22 secs washing and 8 secs drying is still 30 secs in total, whether it's done separately or not. And as you mentioned, the number of sinks and the number of dryers are balanced, so they combined have a similar throughput. I think you see sink lines more often just for that reason, if the sink line can handle 10 persons per minute, and the supply is 20ppm you will have a queue. But once we throttle people at the sinks, the supply to the driers is 10ppm, thus no lines (assuming the driers line is 10ppm)....

[sliverstorm]

Forget about potential speed pitfalls, and consider the following: If your hands leave the sink dry, you no longer need a regularly cleaned tile room to keep things sanitary, because nobody will be dripping/flinging water everywhere. Where might you be able to put sinks now, or how might this change a washroom? That's what is really interesting to me right now.

[dpcx]

This also allows you to remove towels and several trash cans, and add additional stations.

[btgeekboy]

Does it though? While I agree with your premise, what I often see are available sinks while everyone hangs out around the 1 or 2 dryers or towel dispensers and trash cans, waiting for their hands to dry.

That is, unless it's like another place I know of where there's a paper towel dispenser and trash slot between every sink, in which case this faucet wouldn't change anything - they'd just be using their sink instead of standing in front of it with a paper towel.

[tikhonj]

Essentially, combining washing and drying reduces pipelining. It doesn't change the time for any individual person, but it does reduce throughput.

Of course, most public restrooms have fewer drying stations than sinks, so this would probably be less of an issue.

[GigabyteCoin]

It increases the space for more sink/dryer combinations, however.

Side note: As a man, I think the last time I had to wait to dry my hands was half time at a sports stadium, and even then it was only a 20 second wait.