Lessons Learned Part 1: Trapped Air in Plumbing System
This is the beginning of a weekly series where we will discuss certain situations or complications that have arisen during certain projects, how we addressed these situations, and what we can learn from them. Through this series, we hope to not only prevent these issues from happening again, but to also provide you with the information to prevent them from happening at all.
A recent project in downtown San Diego had us removing an out of date existing booster pump system and replacing it with our proprietary booster pump system design. After installing and testing out the new system, it came to our attention that the pipeline from the city to the booster pumps was rattling and swaying far beyond normal operating levels. Upon further inspection, we found that this movement was only occurring during the start-up and shut-down of the booster pump system. Together these were signs that the likely cause may be air being trapped in the pipeline.
We found that, during the construction of the building, the pipeline had been elevated in order to make room for the conduits, which, without a proper air bleeding system in place, creates an increased probability of air being trapped along the elevated portion of the pipe. Because air is lighter than water, it tends to gravitate toward the high points of a system. When this air gets trapped, it can restrict all or part of the flow through the pipeline. Due to this restriction, the pressure increases forcing water to flow at a higher velocity through the confined space, increasing the level of pipe movement. Allowing this abnormal movement to continue could potentially cause the pipeline to fail.
To address this issue, we installed an air release valve on the elevated portion of the pipe, where the air is most likely to congregate. The air release valve does just as its name implies, vents out the air that builds up within the system, allowing for smooth and efficient operation. It is important to ensure that it is installed at both at the highest point of the system and at an area close to where the pipe descends back to the normal elevation, as the flow of water pushes air pockets into that area.
After installing the air valve, we refilled the system through the supply side and bled all of the trapped air out of the pipeline. We restarted the booster pump system and found that the level of pipeline movement had been reduced drastically, returning to normal operating levels.
As we move toward more sustainable, green building practices, it is imperative that we account how to adapt existing infrastructure to those practices. In this case, the existing booster pump system was inefficient and, because it was continuously running, increased overall energy consumption. The new system cycles on and off based on water usage and pressure, which effectively reduces energy consumption but increases the effects of air being trapped in the pipeline. Because the older existing pipeline was not installed to meet the requirements of the new system, we had to adapt it by adding the air release valve to the high point, which corrected the problem. The new booster pump system now functions without issues, and creates an estimated 51% reduction in energy costs and 89% reduction in maintenance costs for the building.