This summer I had the opportunity to participate in BLOOM’s Water Monitoring workshops, and there were some questions about whether using hose meters when monitoring water use would impact water pressure. Uncertain of the answer, I decided to run a little experiment.
In theory, the pressure will be reduced because of the Venturi effect (a phenomenon that results in a reduction in pressure when a fluid flows through a narrow section of pipe). This results in a pressure decrease and a velocity increase.
For the test, I used a pressure gauge connection, a ball valve, and a Gardena flow meter. The test was conducted on my well system that operates from 40-60 psi (slightly lower at outside tap) which may not be the case for all installations. I installed the pressure gauge to the hose, and connected the ball valve to the gauge. I throttled the ball valve to create some back pressure, and ran the water for 5 minutes monitoring the pressure at the gauge.
Next, I installed the Gardena flow meter between the hose and pressure meter and repeated.
The difference in pressure readings was not appreciable, although a slight increase in velocity (travel distance of stream) was evident, indicating that the pressure did drop somewhat. The actual pressure drop could be calculated by the velocity increase, but doesn’t seem necessary.
An interesting finding was that the cause of any pressure loss does not seem to be the meter, but rather the convenient quick connects supplied with the unit. These can removed without affecting the operation of the meter.
Conclusion: While the test was not scientifically conclusive, it showed that hose meters should not reduce water pressure appreciably. If you do experience a drop in pressure try removing the “quick connects”.
Ted Bailey is President of Aureus Solutions Inc. an environmental consulting firm based in Kingston, Ontario.