Here is my situation.

About a week ago my wife heard a "loud" knocking type noise in our basement. Closer inspection revealed that when a toilet would flush, the Pex cold water line was knocking against the floor joist, causing knocking sound. Did an internet search, came up with "water hammer" or "water resonance". Tried a couple of suggestions on the web, still does it when we flush any toilet.

This has never happened before.

I did check our meter, it was leaking, so I called the water company and they fixed it. No more leak, but it didnt fix our problem. I feel like that is what caused it, but not sure.

Can anyone shed some light on this?

You say they fixed the leak but I’m wondering about the pressure coming in????
Just a thought.

B

Installing an expansion tank should fix the hammering

The pressure seems to be on par with what it was before the leak or the sound.

When you flush a toilet, you can hear it when the tank is filling back up, its like a "pulsing" sound

Have you replaced the tank valve/float??? I’m thinking I would start there.

Sounds like a pulsating tank fill valve to me if it only happens when you flush the toilet. If it is doing to several toilets it is either the valve or the pressure has increased causing the valves to do it,

Shut off the supply lines to each toilet.........one at a time. Then shut them both off. See how it reacts one at a time. Turn on faucets at sink & shower to see if it still is knocking. At least you may be able to isolate the problem.....if there is one.

You can stop the knocking by clamping the Pex line to the joist

What would cause the sudden increase in pressure? My in-laws live right next to me, they are on the same water line, they aren’t having the issues that I am. Like I mentioned, it just started out of the wild blue.

I went into the basement where the main comes into the house and had my wife flush the upstairs toilet, then the 2 on the main floor, same thing every time. The main water line pulses like a heart beat, which has never occurred before. It’s way more pronounced when someone flushes the toilet, then opens a faucet or starts the shower.

Maybe you have a water pressure reducing valve that went bad. Some homes need them, depending on the location of the home in relation to the water supply tank to prevent damage to plumbing from too much pressure.

Had to replace mine last year and it completely fixed exactly the problem you are describing. It’s about as easy of a plumbing job as there is.

I’m on county water, meter is out next to the road. This water pressure reducing valve, where would it be located?

For it to work right would have to be in the incoming line before anything is split off. Here is a link with explanation and pictures of what to look for. pressure valve

You can not compress water, when a valve is shut off abruptly you get water hammer. The weight of the water moving through the line comes to a complete stop and it shakes the pipe. A handy man's fix it to put a air chamber in the line. The chamber in the water line has air inside and will cushion the water and stop the water hammer.

Used the bathroom in the middle of the night, flushed our toilet, could hear it immediately in the basement.

I guess Im confused as to why it started so suddenly?

Do you think its a single problem, or could it be several issues together?

Its getting annoying!

If all of your faucets and toilets create the noise, then it is my opinion that it is a system issue.....like a pressure valve.....rather than a single fixture causing the problem

The Pex is clamped to the joists, just in that particular spot the clamps were further apart than normal.

If nobody has flushed a toilet or anything, my water pressure seems to be normal, like always. I turn my shower on, no issues. If someone flushes a toilet, then turns on a faucet or shower/bath head, the water pulses out, if that makes sense.

I called a plumber yesterday, but have not heard back to see when he can come take a look.

Would the pressure valve be located at the meter? Obviously my water line goes from the meter to my house, which is underground.

If its not at the meter, where would it be? I have a simple shut off valve in my basement where I shut the water on/off

Still feel like the problem was created from a leaking water meter, but not sure. The water company is responsible for the meter, but anything past that is the owners issue.

My pressure reducing regulator was about a foot above my shutoff valve where the supply line comes into my house.

I'm no plumber but I have done a lot of it. It seems to me that it COULD be air trapped somewhere in the line. Either a high point or low point.......where it can't get out. I HAVE seen that in fuel lines. For every drop that the meter leaked, it would likely admit a tiny bit of air also.

I would suspect that any pressure valve would be located after the line enters your basement. It could also be at the meter but I suspect not.

I have a valve on my system that allows me to change the pressure just with a screw driver. Maybe there is something like that at your meter that got bumped or otherwise altered when they fixed the leak. Just spitballing