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RepWars Briefing - Questions & Answers
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Question...
"I have run into an odd problem on a few recent jobs. When a toilet is flushed, the pressure drops from approximately 65 psi in the water main serving the toilet bank to 40-45 psi and a large amount of pipe movement occurs. A noise similar to water hammer is observed but this problem occurs immediately when the flush valve opens, not as it closes.
The toilets are supplied by either a 2 1/2" or 3" end to end water header with water hammer arrestors on both sides of the toilet bank. Static water pressure remains at 60-65 psi with no use. Flush valves are Sloan Royal #111 and #8111 (for handicapped). The toilets are either Crane "Placidus" or Kohler "Kingston Lite."
Frankly, I'm stumped. It seems that the initial velocity of water flow when a flush valve opens is so great that the force imparted on pipe turns causes the pipe to sway. I can't figure why this is happening and why it happens only on a few jobs and not all. If anyone has suggestions or ideas, please email me. Thanks.
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RepWars Reply...
You have an interesting problem that could be the effect of various circumstances. The following are items you should check to diagnose the cause:
Based on the pipe sizes you listed, the flow of one flush valve would not created enough velocity to decrease pressure as drastically as you mentioned. (Unless the distance from the water supply and the fixture is extremely long). This indicates the possibility of a restriction somewhere within the piping system. Restrictions can be caused by; One or more line valves that are not fully opened, corrosion within the piping that reduces inside diameters, foreign objects within the piping, plugged strainers, undersized water meter, etc. Check these and similar items.
The piping should not move if properly supported and if water hammer arrestors are sized adequately. Make sure the installer has provided supports in accordance with industry standards and that arrestors are sized and located per manufacturer's recommendations. Also insure that all air has been bled from the system and that no additional air is being introduced.
If a booster pump system is involved, verify the pump capacity, suction pressure and how the pressure tank maintains it's air charge.
Verify how the system reacts when other fixtures are operated such as faucets.
Verify how the system reacts at various locations within the facility. This may help narrow down where the problem is located.
Consider using pressure regulators on main(s) to reduce static to 40-50 psi. (Only if this facilitates proper operation of all fixtures and equipment).
Hopefully, this will help you find the problem. Let us know what you discover and feel free to forward any additional information that may reveal other possibilities.
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