Water Pressure- What are the issues?- 2

This Engineer believes that issue number 2 has or will cause legal concerns for the design engineer or the contractor. The water closet-flush valve combination require a minimum water pressure for operation. These pressures during the test are set at maximum value of 35 psi pressure. The manufacturer advertises their operating pressures range from 15 psi (one manufacturer and only one model) to 25 psi (majority of models). Some manufacturers are calling static pressure and some call it flowing pressure.

Engineering calculation, majority based on basic Bernoulli’s equation, is strictly static pressure (Energy content of the water in terms of standing water within the pipe) calculations. Assuming the velocity pressure is not critical.

There are many towns that the street pressure is near 50 psi or below. Pressure losses through the system are:
• through the meter, backflow device,
• static height,
• distance of run and
• minor losses.

There are only two choices for the Engineer: Increase the pipe size (material cost impact), or introduce booster pressure (space and cost impact). Engineers must be interested in this issue for several reasons; improper design will cause an invitation by a legal council, loss of time and money on an installed facility that is not fully functional.

The testing labs are obligated to test at these higher values. However, it does not stop the manufacturer to better design their plumbing fixtures to match the only model tested at 15 psi. Manufacturer can request the testing agency to test at lower pressures as well and they can publicize the findings. My personal opinion is that the Plumbing Manufacturers’ have no incentives to promote their research and development and pursue in breaking the technology barriers. As long as the Engineers and Contractors specify these units, the manufacturers will not alter their existing designs. Therefore status quo will remain in place.

Plumbing Engineers and Plumbing Contractors must voice their request for more research and development to the manufacturers. In addition, we must show our support manufacturers with more research and development.