Are the traditional methods of sizing domestic hot water production equipment in hospitals obsolete? Are engineers installing more hot water production equipment than needed? Are we wasting energy by not “right sizing” the production equipment?

These are all good questions and the answers can impact hospital’s energy use and operating costs. 

Recently, engineers have started to re-evaluate how we size domestic hot water equipment. There are many accepted industry standards that can be used and have been used for many years. But are these standards keeping up with the changes in hospital design and operation? 

For example, low flow fixtures are being used in all of BSA LifeStructures's designs where possible. Have the sizing methods taken this into account?

Patient stays are becoming less lengthy and in many cases, if the patient can get up and take a shower, then they can (and most likely will) rehabilitate at home where they can take a shower in their own bathroom.

Patient showers are not used with the frequency of the past, so should showers be eliminated from most patient rooms? Perhaps this is a question better answered at a future time. 

Let’s look at an example. BSA LifeStructures recently designed a new hospital bed tower with 130 beds. All the traditional design calculations relating to domestic hot water use indicated the demand would be between 58 gallons per minute (GPM) to over 200 GPM, depending on the method selected. Ultimately, we chose a system at the lower flow rate, but configured it for added capacity if the hospital needed it in the future.

The design team also installed a flow meter specifically for the domestic hot water flow to find out the affect that low-flow faucets and shorter patient stays would have on demand flow. After collecting a year’s worth of data, the peak flow was 38 GPM or only 66% of the lowest forecasted flow! Further scrutiny of the data also revealed that this peak only occurred once for a very short time with most peaks around 30 GPM. 

Energy codes and the standard care of design require the engineer to minimize energy use in all buildings including hospitals. In doing so, it is imperative that we understand the demand of the domestic hot water system in order to right size the equipment and to design the most efficient system. 

Designers need to continue to monitor the demand of all the systems within a hospital and specifically the domestic hot water system. This information will help us understand the dynamics of a changing environment and enable us to design with cost and operational efficiency in mind.

John Sauer, PE, LEED AP, is Senior Director Engineering Design at BSA LifeStructures in Indianapolis. John is a strong advocate for sustainability and the use of energy-efficient design in traditionally high-consuming healthcare environments. John has leveraged his knowledge of heating, ventilation, vacuum, air conditioning, steam distribution, energy centers, and piping design to identify cost efficient and sustainable solutions for all types of healthcare facilities. He can be reached at For more information, please visit