In the city of Houston, we’ve had two major interruptions in water supply in the last 18 months. Unfortunately for many buildings, they didn’t find out until their tank and piping were dry and it was too late to act.

With a Level Control Panel from Cougar USA, you can monitor incoming city water pressure and receive an alarm as soon as the pressure drops, giving you time to conserve water and warn patients, tenants, and guests of the situation.

Monitor City Pressure on Fill Stations Tech Talk Transcript:

Hi I’m Tim Zacharias, with Cougar USA. In this Tech Talk, we’re going to cover Monitoring City Pressure on your fill station so when you have a flooded suction application, like in the city of Houston, where we have the code requirement to go through an atmosphere storage tank, like this before your booster pumps.

For a pump system to perform a low-flow shutdown, it must first be able to measure the flow demands in the system. Flow Switches and Flow Meters are mechanical means of measuring flow, which can work, but both require proper installation in the system piping for proper readings. Space and piping constraints can limit the installation of switches or flow meters.

The outlet pressure is determined by two factors. First is the number of floors the PRV Station is serving, and the second factor is whether the station is feeding the floors above or below the station. A good rule of thumb is that each floor will result in a pressure change of 5 PSI. If the floors fed by the PRV Station are the floors above, then you would need a higher outlet pressure at the PRV Station (around 65 to 75 PSI) because the pressure will drop about 5 PSI each floor higher in the piping. If the PRV Station is feeding the floors below, the outlet pressure would need to be lower (around 40 to 50 PSI) because the pressure will increase 5 PSI for each floor lower in the piping.

Many commercial buildings use storage tanks for Domestic (Potable) and Fire Water Applications, especially in Houston where it is required by Houston Amendments to the Uniform Plumbing Code Section 607. As water is used in the building, an automatic system is required to replenish the water and maintain a constant level in the tank. In domestic applications, this process can repeat multiple times an hour during peak demand loads. An automatic level-control system has two main components, Fill Valves and Controls.

Float Controlled Valves (Cla-Val model 124-01) are widely used on break tanks in commercial buildings. Float valves operate on the same principle as the valves in the back of a toilet: a float attached to a rod moves up and down with the level of the water in the tank. Float valves are simple and effective, but there are drawbacks in commercial applications. Most valves are installed on the top of tanks with the float rod directly attached to the valve, making them difficult to access and maintain. Tank-water-level adjustments are also difficult because the float rod length and float position must be changed on the valve itself.

When two float valves are used, there is no alternation between valves. The lead valve (shorter float rod) will always operate first, with the lag valve going long periods without use. This combination will eventually cause failures in both valves without proper preventative maintenance. Also, these systems typically provide little or no feedback to the Building Management System.

Pressure Boosting System Design has also seen drastic changes in the same time period. Fifty years ago, large constant-speed, single-stage, centrifugal-pump systems were the design standard. These workhorses run 24/7, 365 days a year, regardless of the system demand in the building. This results in wasted energy and unnecessary wear on the pumps and piping. With smaller flow demands today, older pumps still in service are grossly oversized, making them much less energy-efficient.

More than 60 years ago, the late Dr. Roy B. Hunter developed a system for calculating water loads in commercial buildings. The estimated water demand of fixtures (water closets, sinks, etc.) is given a value called Fixture Units which have an equivalent demand load in Gallons Per Minute (GPM). The Fixture Units and Demand Load relationship is known as Hunter’s Curve and is still the basis for plumbing system design today.

Hunter’s Curve can be effectively used to calculate total system demand, but it has a glaring flaw. There is no consideration for diversity in the system demand. Using Hunter’s Curve for the basis of design of a Pressure Boosting System results in a pump system sized for all fixtures being used simultaneously, a scenario that will likely never happen. The pumps are grossly oversized for partial-demand conditions which make up 90% or more of total operation, causing poor system control and unnecessary wear on the pumps and piping system. In addition to Hunter’s Curve, Cougar USA uses field experience and data collection for system design.

To generate an accurate demand load profile, we gather as much information as possible about the building. The type of building has a huge impact on the load profile; even with similar fixture units, hospitals, hotels, schools, and office buildings will all have different load demands throughout the day and week. Special applications, the height of the building, locations of equipment, and potential future expansion are all factors in creating the right Building Load Profile. Once the system requirements are determined, we must make the right equipment selection.

In 2017, about 39% of total U.S. Energy Consumption was consumed by the residential and commercial sectors. In a commercial building, HVAC equipment (i.e., chillers, boilers, cooling towers, etc.) and lighting are the biggest targets for energy savings, but the capital costs for improving these may be prohibitive. There are many opportunities for energy savings and building performance improvements with other systems in commercial buildings.

Pumps are used in a variety of applications in commercial buildings, and 90% of them work inefficiently. There are three main reasons for pump inefficiency: pump type, size and controls. The proper combination of pump type, size and control will ensure the best system performance and lowest energy costs. Unfortunately, most pumps installed today are either improperly applied or sized and use outdated controls.

Domestic Water Pressure Boosting Pump Systems are required any time the city water pressure is too low to deliver water to a commercial building. Mid- to high-rise buildings almost always have pressure-boosting systems, and many single-story restaurants and medical facilities require high water pressure for special applications. In our experience, these systems usually suffer in all areas of inefficiency. Most are designed using fixture unit counts and maximum flow demands without looking at diversity factors and partial-usage loads. These calculations cause pumps to be oversized and incapable of performing well under partial-load conditions, which accounts for 90% or more of the total operation.

Pressure Boosting Systems are essential for delivering water to high-rise buildings; however, the method for sizing these systems has not changed significantly in over 50 years!  Cougar USA’s High-Performance Design approach combines our extensive knowledge & experience with the best products on the market to deliver systems that provide constant water pressure with little to no downtime and the lowest Life Cycle Cost.  Check out this three-part Tech Talk series on Booster System Design to see how we do it.  We will cover the flow and pressure requirements of a building and pump & system selections to meet them.

Pressure Boosting Systems Design Part 1 Tech Talk Transcript:

Hi, I’m Tim Zacharias with Cougar USA on this Tech talk, this will be the first of a three-part series for sizing and selecting pressure boosting systems. On this one, we are going to be looking at the flow rate for a commercial building.

Now, a couple of different things that we need to take into account when we are looking at flow. The first place that we can start is Hunter’s curve in the fixture unit counts. This is a method that goes back to the 1960s. Basically, we can count up our fixture units in the building, look at the chart for what that says the equivalent flow rates are, and what that is going to give us is our worst-case flow rate for that building.

High-rise buildings present multiple challenges for water distribution due to the high pressures required to reach the top of the building. The high pressures in the lower levels of the building cause high-pressure drops across Pressure Reducing Valves (PRVs), over 100 PSI or more, creating the potential for cavitation within the valves.

Cla-Val explains cavitation in this white paper, saying “Cavitation occurs when the velocity of the fluid at the valve seating area becomes excessive, creating a sudden, severe reduction in pressure that transforms the fluid into a vapor state, resulting in the formation of literally thousands of minute bubbles. The subsequent decrease in velocity and pressure rise that occurs after the valve seating area, when the pressurized condition resumes, causes these vapor bubbles to collapse at the rate of many times per second. Should this occur in close proximity to any metal surface, damage can take place. Over time, this can lead to valve failure.”

The damaging effects of cavitation include excessive noise, erosion of the valve and eventual valve failure. When designing a system with pressure drops greater than 100 PSI, there are two ways to avoid cavitation.