I notice a tapping sound when the toilet flushes at the far end of the of the house (farthest from where water enters house) or the drip irrigation system turns on (also at the far end).
In the case of the toilet, the sound fades as the toilet fills and shuts off. In the case of the drip system, the sound fades after a few seconds, which I imagine to be the time it takes for water to fill the drip tubing. The sound is most noticeable in the master bathroom where the water enters the house, but flushing the toilet in that bathroom does not cause the sound.
Is this water hammer? Is it likely to cause damage to the plumbing?
Any ideas how I can fix this?

Water hammer is one big thump, how many noises are you hearing or is it more like click, click, click?

Bob's bang on! This isn't water hammer. Knocking, popping, creaking and crackling pipes are a common complaint, especially in colder weather. I can tell you what's happening and take the mystery out of it but you're not going to like the repair. When a draw is made on a hot or cold water line in a coold chase the line expands against a pipe strap next to a stud and when you drain water from your tub or shower it goes into a chase that is a little cooler then room temperature. The heat expands the pipe causing it to rub against the stud to which it is pipe strapped. This is the sound you hear. As it cools it contracts and the noise is heard again. To repair it you must tear open the walls and locate the pipe strap that's causing the problem and shim it tight. Most people when they learn what causes it just elect to live with it. Good luck and thank you for rating my answer. Tom

Water hammer is one big thump, how many noises are you hearing or is it more like click, click, click?

I would describe it as a thump, thump, thump.. but yes, it's somewhat periodic.
The noise starts loud and fast, then gradually slows down and gets softer until it stops, but you can now just hear the sound of water running through the pipes (normal, in other words).

Cold water? Sound loudest where water enters the house?

Do you have a pressure reducing valve?

Bob's bang on! This isn't water hammer. Knocking, popping, creaking and crackling pipes are a common complaint, especially in colder weather. I can tell you what's happening and take the mystery out of it but you're not gonna like the repair. When a draw is made on a hot or cold water line in a coold chase the line expands against a pipe strap next to a stud and when you drain water from your tub or shower it goes into a chase that is a little cooler then room temperature. The heat expands the pipe causing it to rub against the stud to which it is pipe strapped. This is the sound you hear. As it cools it contracts and the noise is heard again. To repair it you must tear open the walls and locate the pipe strap that's causing the problem and shim it tight. Most people when they learn what causes it just elect to live with it. Good luck and thank you for rating my answer. Tom

I would agree except for the fact that the thumping sound doesn't last the same length of time for each circuit. I have four valves on my drip system. Each valve controls a different length of line and the legth of time the thumping lasts seems to be determined by the length of the drip line being used. Drip lines with higher water flow have louder thumping, lines with longer runs have longer lasting thumping. After a few seconds, the lines get quiet and all you hear is the water running.
One thing I read online was that this could be caused by air in the lines. I've tried their suggestion to turn on all spigots and then shut them off one by one to flush the air out, but that had little effect.
You're right, if the solution comes to tearing into the walls, I could convince myself to live with the problem.


Cold water? Sound loudest where water enters the house?

Do you have a pressure reducing valve?

There is a pressure reducing valve on the far end of the house, to drop pressure for the drip system from 60psi down to 30psi.


Cold water? Sound loudest where water enters the house?

Do you have a pressure reducing valve?

I didn't answer all your questions:
Yes, cold water.
Yes, loudest where water enters house.
Pressure reducing valve only on far end of house (for drip system). House pressure at that point is 60psi.

No PRV on main? I'm suggesting you have faulty PRV (or has trash in it). Of course could be one of PRV for drip system. Close valves to drip system and see if toilet still creates taping.

No PRV on main? I'm suggesting you have faulty PRV (or has trash in it). Of course could be one of PRV for drip system. Close valves to drip system and see if toilet still creates taping.

Yes, toilet causes tapping by itself.
If there's a PRV on the main, it must be buried.

With drip system turned off? Not to disagree with Tom but I'm having problems seeing how the use of cold water creates pipe expansion and at the entrance to the house.

With drip system turned off? Not to disagree with Tom but I'm having problems seeing how the use of cold water creates pipe expansion and at the entrance to the house.

I don't think it's pipe expansion either. The problem is most noticeable (loudest) with the drip system but the fact that it's there for all valves and the toilet makes me think the problem is in what they all have in common - the house plumbing.

I agree with Bob and bettinaz, It's not pipe expansion. You say the thumping continues even after the drip system's shut down? And its loudest where the water enters the house? What's the street pressure? Regards, tom

I agree with Bob and bettinaz, It's not pipe expansion. You say the thumping continues even after the drip system's shut down? And its loudest where the water enters the house? What's the street pressure? Regards, tom

No, the tapping stops a few seconds after the drip valve opens. There's no sound at all when the valve closes. I hear it where the water enters the house, but have been unable to hear it at the water meter. I may not be able to run out there quick enough.
I don't know the pressure at the street. I only know at the input to the drip system it's about 60psi.
I have recently upgraded the drip system and am wondering if it may be the reason I'm now hearing this more loudly than in past. Is it possibly an effect of my regulator trying to adjust pressure? That probably wouldn't explain why the toilet has always made the noise though.

Brett


I agree with Bob and bettinaz, It's not pipe expansion. You say the thumping continues even after the drip system's shut down? And its loudest where the water enters the house? What's the street pressure? Regards, tom

I think I found the source of the sound. I sounds like its coming from the water meter itself. The sound is actually louder inside my bathroom, but there is a sharp click sound at the meter when the water is running fast.

Brett

I think I found the source of the sound. I sounds like its coming from the water meter itself.
The water meter has a little paddle wheel that turms as you draw water. That's what you hear. Have the cuty change out the meter. Good luck and nice job of tracking down the sound. Tom