Pressure Fluctuations

[JMH]

Our water system is having major pressure fluctuations. They are ranging from 85 psi to 185 psi in a 15 second time period. We have a pressure gauge measuring the pressure every 15 seconds, 24 hours a day and have moved this meter to other locations. We are seeing this fluctuation throughout the system and know that our meter is reading correctly. Also, we are getting alot of complaints about people's PRVs going bad at their home and pop-offs failing on their hot water heaters. Any ideas?

 

[Ahmedv]

Hello
The pressures youve quoted are extremely high. Is this pressure reaching the end user?
There are gadgets that can absorb minor shocks in water reticulation piping, and these have been fairly successful in preventing potable piping system failures.

Regards Ahmed Vawda
Process Engineer
Al Khaleej Sugar - Dubai
avawda@aksugar.co.ae

 

[mikolay]

I agree you have very high, and perhaps dangerous pressures. The rapid change in pressure sounds like a water hammer problem. Is this pipeline fed by a well, or what other source. The pump going on and shutting off could be your source of hammer. do you have a dampening check valve in place after the pump?

 

[JMH]

We do have wells as our source which are pumped into the system. There are no dampening check valves after the pump. That is an idea worth pursuing. There is a notable increase in pressure fluctuation when pumps are starting and stopping. However, when we are not pumping we are seeing large spikes sometimes in the middle of the night or at other random times. We suspect this is due to a very large industry that operates 24-7 and are in the process of purchasing a flowmeter to compare their usage to that of the pressures throughout the system. What is known about these gadgets that can absorb minor shocks for possibly placing them at the customer's meter or maybe at the entrance to some subdivisions? We do have some PRVs in areas but these sometimes don't react quickly enough for these spikes in pressure

 

[civil21]

JMH

Can you correlate the pressure spikes to pumps turning on or off? Valves opening or Closing and the like? If you can, this could be a classic example of water hammer.

 

[civil21]

JMH
Sorry, I didn't read all of the entries before my first entry.

 

[Durst]

From the way you describe the pressure fluctuations, it sounds like either you have
a "bad" PRV wherein the sensor lines may be leaking, plugged, or otherwise deteriorated, a malfunctioning valve actuator, a damaged soft start on a pump, or a number of other scenarios.

A quick solution would be to install a surge anticipator valve in the line and route the outlet back to the reservoir/tank until the problem can be isolated.

 

[bargin]

I have a similar problem in a municipal water treatment plant. Pressures constantly fluctuate from 75 psi to as high as 115 psi. I think I may have solved the problem. The pressure reducing valve used is a 6" which is too large an it has a minimum flow range. When flow rates are low, the valve continuously opens and closes. I installed a low flow bypass on the PRV the fluctuation stopped. Other option was to take out the 6" and install a 4" which would have lowered the minimum flow range it operates at.

 

[ivanlocke]

Most pressure reducing and relief valves can be easily fitted with a limit switch from which you could monitor the openings/closings and see if it correlates with your pressure spikes. If the it is one industry that is causing these problems, you may be able to regulate how often and for how long they draw water (we had a problem with a company kicking on and off every half hour for 10 minutes during the night and were able to get them to change their system to draw less often for a longer period). Or as bargin said have several smaller valves in parralel set at slightly different pressures.