Why does water pressure spike immediately after using cold water and stays...

garage_greg

Our contractor installed a pressure regulator because pressure was too high on the side of the house where we remodeled bathrooms. I measured pressure and it was around 78 but after using cold water only, the pressure spiked to 108 and remained for several days until I released water from the hose bib outside. We refrained from using any hot water. Then I measured the pressure and it was 80, then ran cold water and it spiked to 108 until...

Originally asked by Cewe on Stack Exchange (diy) (CC BY-SA 4.0).

uphilltech

Great question — answering as the UphillTech team:

It is almsot impossible to install it wrong, but then there are always some who find the way. When you open the faucet the pressure will drop (that is normal) and the regulator compensates by increasing the pressure to the set value. If you have one of those quarter turn ball valve and closed it rapidly the regulator has no time to react/adjust. Regulator only works when water is flowing, and does noting when there is no flow. Before you mess with replacing regulator try following. Very slowly close the valve and observe the pressure now. You should do it soon, because the very high pressure can damage your plumbing.

Full answer by DIY75: https://diy.stackexchange.com/a/296671 (CC BY-SA 4.0).

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