System Constraints can slow a system's output.
Within days of replacing a bathtub spout that leaked most of the hot shower water down the drain, the shower had stopped completely. No water from the spout. No water from the showerhead.
Yikes?! Where was all the water going?
Turns out a broken flow restrictor was plugging the showerhead. Since the showerhead was old, the increased water pressure from the new tub spout caused the restrictor to crumble and plug the showerhead.
I cleaned the debris from inside the showerhead, but now it leaked all over. Time for a new showerhead.
Disturbing Balanced Systems
Standing in line at Home Depot with a new showerhead in hand, I reflected on what just happened.
The old shower system pieces had been working together for a long time: it was a balanced system. It was inefficient, and costly, and delivered poor results – but it worked. Installing a new spout increased the water pressure to the showerhead. This unbalanced the system, and because it was old enough, something gave out – the flow restrictor.
Taking a system view: What had happened was the removal of a constraint (the leaky spout) improved the system (better flow to the showerhead). Then a new constraint, (the old flow restrictor), prevented the overall system output from improving.
This got me thinking about improvements to business systems. Sometimes when we improve a system, we do not get the results we were expecting. It may not be as dramatic as my showerhead, but the expected increase in system output and/or reduced costs does not occur.
The reason will be a new constraint within the system. You will find the new constraint in one of two places:
- Between your recent improvement and the final output, or,
- At an earlier system stage.
Eliminating one constraint always activates a new constraint.
This does not mean failure: after all, the overall system improved. Maybe just not as much as expected.
For example, consider a retail furniture business as a system. (A business is system of systems working together.) One of the functions of the business is to get customer orders and deliver the product. The more throughput the better.
The Sales system brings in orders. The Shipping system gets the ordered product to the customer. In order to increase business throughput the owner improves the Sales system and double the number of orders. Awesome. But all is not well. The Shipping system does not reflect a similar increase in output. What happened?
Shifting Constraints
The constraint has shifted from the Sales system to the Shipping system. The problem is Shipping has a single truck and crew, and they were nearly max’d out before the improvement. They can handle some of the increased demand, but not all of it.
Now, orders are backed up all over the shipping room floor, deliveries are late, and customers are grumpy. The expected results were not achieved and an unexpected consequence arose. Although Sales is much more effective at getting the orders, the business as a system can’t deliver them all. It is the equivalent of the flow restrictor in the showerhead being unable to handle the increased pressure.
Now, the owner has to work on the Shipping system. The shipping constraint must be removed to get the overall business system working even better. It might mean adding another delivery truck and crew, or just adding another crew and running them in the evening. Which solution to use will require a bit of cost analysis first.
System improvement is an on going process of innovating and removing constraints. When you improve a system, don’t be disappointed if you do not see the expected big improvement. You just need to look for the new bottleneck and work on it. Overtime the system will get better and better.
When considering a system improvement, look for impacts on other parts of the system. Look for impacts on other systems that either feed into, or take outputs from, the modified system. To get maximum benefit from the improvement you may need to:
- Adjust upstream and/or downstream stages within the system.
- Adjust other systems that either feed into, or take outputs, from the modified system.
With a bit of examination you can plan accordingly. For example, in the retail furniture store, thinking about the downstream systems would have highlighted the inability of the Shipping system to handle the higher volume. Knowing that, the owner could have planned better for the increased order volume.
Not all system improvements are as impactful as doubling sales. Most improvements yield incremental benefits. Regardless though, a bit of thinking will help yield expected results without unexpected consequences.
As for my showerhead, once I installed the new one the whole system worked like a charm. Now we have showers without wasting hot water, and we are saving some money.
