Hi All, I need some advice. We moved into our home in 2009 (built in 2002) and it has PEX plumbing throughout the home, with the manifold in the attic. The water pressure has never been very strong but it was OK enough to use. About 8 months ago we started hearing what sounded like a 'pumping or pulsing' sound when the water would be turned on in the house. The noise would STOP when the water was turned OFF. It happens every-time the toilet tank fills (after being flushed), when the clothes washer fills the wash tub, and when we turn the hose in the front of the house (where the water from the street comes in). It sometimes happens when someone is in the shower, or when two or more sinks have water running at the same time. Recently, the noise has gotten quite LOUD when water is running, and we have noticed that the cold water pipe (that goes into the water heater), is vibrating a little. I know that water hammer is caused when flowing water is turned off, but I have no idea of what could cause the noise when water is running?? I called the water department, because they had recently done some work on our street, and they came out to measure the water pressure. The water department rep tested the water at the street and said it was 80 lbs, and the pressure at the hose bib on the front of the house is 70 lbs. I wondered if it might be a case of a bad water pressure regulator (PRV valve) on the front of the house failing, causing the water pressure to be too high coming into the house. but then I remembered, the water pressure in the house has never been high, and still isn't even with the noise. The bathrooms were always OK pressure-wise but the kitchen sink water pressure is pathetic. I'm stumped? Any thoughts, suggestions or advice is welcome and I thank all in advance for their assistance!