RPZ mandate leads to water pressure boosting solutions

With the N.Y.C. Department of Environmental Protection's (DEP) mandate that buildings install backflow preventers (RPZ) at the building's water main, building owners face the task of selecting the proper equipment and controls while considering additional problems, such as adequate water flow, when addressing these requirements. In many of these buildings, water pressure boosting systems are a necessary solution. Real estate owners and property managers struggle with meeting code requirements while keeping operation and installation costs down. Buildings with 350,000 Btuh input boilers (gas or oil), chemically treated boilers, and buildings with water tanks or single wall heat exchangers are now being watched closely by the DEP. Until recently, many N.Y.C. buildings were not under scrutiny by the DEP, but with that changing many building owners are hiring professional engineers to plan and install RPZs. The issue is not only the cost of meeting code, but the ancillary costs of installing and maintaining equipment necessary to solve the problems the backflow preventers create. Backflow preventers are mechanical devices installed in a plumbing system to prevent water from flowing backward into the water system. These devices create a pressure drop between the incoming water main pressure and the delivered water pressure in the building often causing water pressure issues in the top floors of buildings (ie. toilet bowl flushing and shower pressure to name a couple). Not only do building owners have to install RPZs, but they also need to address the water pressure issue. That means a water pressure boosting system needs to be installed using pumps and controls. "The dilemma then is to find the best pump for the job," said Serge Lemite, of Venco Sales, manufacturer's representative of Grundfos Pumps. "Issues are usually in this order: price, installation time, noise issues and maintenance and electrical costs." In addition, most building owners may not know to ask if the pumping systems being installed include the best technology for their application. For smaller booster pump installations, on/off pumps may be used, but these pumps often come at a significant price when it comes to maintenance, needing to be rebuilt or replaced. When using variable frequency drive (VFD) pumps, there must be consideration for increased failure rates for large and small building applications. Current booster pumps are divided into two basic types. The first is a set-up of two or more on/off pumps in a light commercial environment, usually installed in a mechanical room. The pumps are base mount centrifugal pumps mounted on a steel base with a control panel. "The pressure is delivered at a pre-set rate so the pumps cannot over-pressurize or deliver more pressure than desired," Lemite said. "This method of turning pumps full on and then reducing the output is terribly wasteful from an electrical standpoint. Associated maintenance problems include overloading and burning pumps and pump seal leaks." The second type of booster pump system most commonly seen includes two or more variable speed pumps. "This method of turning pumps on at varying speeds is usually more energy efficient," Lemite said. "Many of the associated maintenance problems seen include pump motor insulation failures, burned windings and damaged motor bearings because the motors selected are not suitable for VFDs. These systems are typically very noisy." Grundfos Pumps offers a quieter, more efficient solution to the booster pump system selection process. Its BoosterPaQ System utilizes vertical multi-stage pumps, which are the quietest in the industry. "This system provides for long term operation, lowest cost of ownership, highest reliability and quietest operation," Lemite said. "Another issue is pump seal leaks. In many cases these seal replacements are off-site and time consuming repairs. We use a cartridge seal, similar to a faucet cartridge, which can be changed on site in as little as two hours. The pump never has to leave the site. " Grundfos manufactures its own VFD Smart Motors, which use less electricity and reduces the costs associated with using smaller VFD drives. The materials used on the system base and water headers are 306 and 316 stainless steel, eliminating rusting and contamination issues. Grundfos makes several types of packaged systems to suit the needs of any project. Its Hydro Solo-E system is a single packaged variable speed pumping station for smaller buildings. The Hydro Multi-E includes two to six pumps packaged in a variable speed pumping station for moderated sized buildings. Finally, the Hydro MPC is a two to six pump packaged variable speed pumping station with control communication out of the box. These pre-set package combinations offer more efficient installation times as well as more defined control options. With many solutions on the market, Lemite offers design assistance to help building owners and engineers select the proper system for each application. For more information, contact Venco Sales at 631-754-0782. Rob Morrison is a sales representative at Venco Sales, Huntington, N.Y.