Bangkok’s Metropolitan Water Authority (MWA) services 8 million people and is focusing on improving pressure management in an effort to reduce serious water losses. With water loss up to 30%, the water authority installed pressure-reducing valves throughout Bangkok and its suburbs. The valves accurately controlled nighttime pressures, preventing leaks and breaks. However, in some areas, high demand during the day caused pressure to drop to 10 psi (0.68 bar) or less. Without sufficient pressure differential, regular pressure-reducing valves would close, cutting off the supply to consumers.
Through Win Wannapanit of Smith Tech Co.—Singer Valve’s representative in Bangkok—Singer Valve learned of this challenge.
“Typical PRVs cannot open when the pressure drops below 10 psi (0.68 bar),” said Eugene Bahia, Singer Valve’s instrumentation specialist. “We were determined to find a solution for Bangkok.”
Bahia experimented with different pilots. One field test that employed a third-party pilot was unsuccessful because the valve was too sluggish, requiring several minutes to open. Additionally, its performance when pressure rose above 10 psi (0.68 bar) was not reliable.
In Singer Valve’s flow lab in Vancouver, BC, Bahia tried again. He fitted a 12-in. (300-mm) valve with a standard Singer PR pilot and a Singer high-accuracy three-way pilot. By installing the custom combination into the flow lab, Bahia simulated various pressure and flow conditions. The results were encouraging.
“Because of the large diaphragm and sensing area of the three-way pilot, the valve required only seconds to open,” said Bahia. “And it remained fully open during the day’s high flow demands, even with pressure as low as 2 psi (0.14 bar).”
When the custom unit was installed and tested in Bangkok, the results remained consistent. Pressure was reduced during high-pressure periods at night. During low-pressure/high-flow periods during the day, the valve opened fully, ensuring a constant water supply to consumers.
“The valve can open at really low pressures,” said Wannapanit, who trained Bangkok’s water operators how to use the valve. “MWA installed numerous 12-in. (300 mm) valves and is very happy with them.”
