Tapping/Knocking Noise in Ceiling/Floor (could it be pipes?)
First, apologies for the long post. I tried to be as descriptive as possible.
I am a first-time homeowner in a new townhouse (moved in 9 months ago). A few months ago in the fall, I started hearing two distinct noises from the same area in the floor/ceiling. Both these sounds occured in the corner of the master bedroom, so between the 1st and 2nd floor. When the master toilet was flushed, I heard a tapping sound, kind of like tapping your fingernail on wood. It would continue for about an hour, and occur every 1-5 minutes. It could be the pipes expanding/contracting. The other noise occured when the shower was turned on and off. It was much louder and from the same spot as the tapping sound. From downstairs, it sounded like the floor creaking and making noise like if someone was walking on it. Upstairs, it sounded like someone knocking their knuckle on a wooden mantle. This would occur for about 1-2 hours, and occur every 1-15 min or so. I had attributed both sounds two the temperature changing outside causing different reactions as the hot/cold water goes through the pipes.
Fast forward to today. The homebuilder sent their handyman out to look at it. They attributed it to air in the pipes since I had closed the outside water valves for the winter. I thought this was plausible as it started occuring shortly after I turned the valves off. He then turned on the outside spigot to force out the air and get the water flowing. I thought this had solved the problem. However, a few nights ago, the loud knocking sound started up again. What concerns me is that this occured for hours (throughout an evening, night, and morning), and it was so loud and annoying that I had to sleep in the guest room. Also, the shower (or any water) was not used in the master bedroom at all. Actually, I haven't taken a shower in the master bathroom for about a month now.
Could this still be air in the valves? Could it be water hammer? The pipes expanding/contracting? Any suggestions on how to handle it? I want to make sure I have an idea of how to handle this before I call back the handyman/plumber to cut holes in my floor/ceiling. Thanks so much in advance.
What you are describing is a classic pipe expansion and contraction. Not likely to cause any harm---
The fix is to open up the drywall and see what the pipe is rubbing against as it expands. Then free it up so it no longer makes noise.
I did this to myself when I plumbed in the hot water heat in my own house 23 years ago.
---Never did fix it!---Mike---