Fluctuation of water pressure

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Love cats

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New water regulator and now pressure fluctuates 5 to 10 lbs. as one to two faucets are turned on. Unrelated to water heater and expansion tank as plumber disconnected hot water line at water heater and attached it to cold inlet on water heater and it still happened. Also still happened with water heater off. My past water heater did not fluctuate this much. This happens with regulator at 55 psi or 65 psi. Expansion tank pressure matches close to regulator pressure. This is my second regulator installed as first one totally failed. Slab leak occured after second regulator installed. Slab leak is repaired but fluctuations still occurs. Do I have another bad regulator? Please respond! Thanks
 

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New water regulator and now pressure fluctuates 5 to 10 lbs. as one to two faucets are turned on. Unrelated to water heater and expansion tank as plumber disconnected hot water line at water heater and attached it to cold inlet on water heater and it still happened. Also still happened with water heater off. My past water heater did not fluctuate this much. This happens with regulator at 55 psi or 65 psi. Expansion tank pressure matches close to regulator pressure. This is my second regulator installed as first one totally failed. Slab leak occured after second regulator installed. Slab leak is repaired but fluctuations still occurs. Do I have another bad regulator? Please respond! Thanks
Just to clarify old regulator failed after many years. First new regulator completely failed-would not hold pressure. Second regulator is having greater pressure fluctuations than original one that lasted man years.. Is this also a defective regulator?
 

Reach4

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Thermal expansion tank air precharge needs to be measured with the water pressure=zero.

Describe the fluctuation. Does it fluctuate while a faucet is turned on to a steady amount? Is it rising and falling every second? Every hour? Rising after using hot water? Rising after using cold water? What is the highest that it fluctuates to?

The symptom is probably due to the PRV. It may be a limitation of that kind of PRV, or it may be a faulty PRV. Less likely, depending on symptoms, could be a failed thermal expansion tank. It could be improper precharge in the expansion tank. It could be that the expansion tank is too small.
 

Valveman

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New water regulator and now pressure fluctuates 5 to 10 lbs. as one to two faucets are turned on.

The smaller the regulator the more reduced pressure fall off it will have. Any regulator will deliver less pressure as the flow increases. With a large enough regulator and you won't notice the 2-3 PSI difference. Small regulators can have 5-10 pounds or more of fall off.
 

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This graph was from http://www.watts.com/pages/learnAbout/reducingValves.asp?catId=64
index.php
 
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The pressure just goes down 5 lbs per one faucet 10lbs for two faucets in use. The pressure does not go higher than the pressure regulator is set it just drops with use. It is a Zurn Wilkins regulator. I will call the manufacturer for a larger regulator for my home. I hope this will help so thank you for the info. Let me know if there is one that is better that you are familiar with. Thanks
 
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