Phantom Plumbing Drip Is All Noise

PVC Pipe behind wallBy Trish Holder

Alliumphobia: n. The irrational fear of LEEKS (or anything in the garlic family).

Okay, maybe my fear of household water damage isn’t quite a phobia, but I’m pretty paranoid about leaks. (That’s leaks not l-e-e-k-s, which are kinda yummy.) So the distinct sound of water dropping each time the kids took a shower upstairs was starting to make me a crazy.

It was a slow, steady “splat” sound that occurred every time the water was turned on in the upstairs bathroom. I imagined little drops of water collecting, unseen behind the walls of my new (green) home. I visualized the whole thing every morning while I listened from my office below. Splat…splat….splat. A fat drop of water, clinging to a run of pipe until it could cling no more. I envisioned the mold that was surely growing in the wall cavity below the upstairs bath.

I called Cliff, my plumber (of course). Cliff said if I didn’t see any evidence of water damage then there wasn’t a leak. Plus, I had a central manifold distribution system, which means there is virtually nothing to leak between the fixture and the water heater. That’s one of the reasons I chose a central manifold system – my irrational fear of leaks.

Still, there was no denying the “splat” sound that lasted the full duration of every shower taken in the upstairs bath. I called Cliff again, who, by the way, is a straight up guy (and if you read this blog you know I’m not one to give contractors random accolades, so you know he must be good). While he still didn’t suspect a leak, he said something about “pipe expansion” and promised to stop by.

Now, by the time I was five years old I could identify the sound of liquid dropping onto a hard surface, so ole’ Cliff was going to have a tough time convincing me that I didn’t have a leak. I know and you know water always finds a way, and when it does there’s always a price to pay. Well, where this story is concerned, I’m happy to report that I’m the one who is all wet.

As promised, Cliff stopped by to troubleshoot the phantom noise. He immediately sent his assistant upstairs to turn the hot water on and asked me to take him to the place where the noise was the loudest. I made a beeline for back corner of the master bedroom closet. We heard the water turn on and sure enough: splat….splat….splat.

“Hear that? Hear that?” I said.

“That’s your PVC drain pipe,” he said.


He called up to his helper again, this time, asking him to turn the hot water off and the cold water on. We listened.

Nothing. No splat, splat–just the sound of water going down the drainpipe. If it had been a leak, why would it only occur when the hot water was on?

The answer is PVC expansion, and as Cliff assured me, it is an annoyance, but not a real problem. The noise occurs when hot water causes PVC pipe to expand and subsequently rub against the wood behind the wall – probably a hole that was drilled for the pipe, but not quite large enough to allow for full expansion.

For good measure, Cliff did a quick inspection of the crawl space to see if there was any sign of water damage from below. It was all dry as a bone, music to the ears of any homeowner.

I have to say it all seemed a little like voodoo to me until he had his helper turn the cold water on and I heard no sound. And then a peaceful feeling settled over me like a warm (dry) blanket. I’d been worried for nothing.

I had to wonder how common this problem was, so immediately after Cliff left (walking over a path of rose petals I’d spread in his honor), I did some Googling. Turns out that distraught homeowners everywhere are posting questions about a mysterious “tapping” sound that occurs whenever the hot water is turned on. It sounds like a leak but there is no evidence of water damage. Occasionally, an experienced plumber tips them off to PVC expansion.

I felt like I’d won the lottery. Not having to worry about an unseen leak was like finding out I didn’t have to have ACL surgery. The noise (like the sound my knees make when going down the stairs) is annoying, but not cause for concern.

11 Responses »

  1. Usually what it is is the pipe rubbing on a stud or joist etc. If you get it away from this surface it will stop.

  2. Thank you for this. I am going to give you full credit and share this on my blogs. I teach ladies about tools and home repair and I think this would make a great addition to my other informaton!

    • The story says drain pipes but Water lines can do this also. I had this happen on one of my projects. Lisa I do presentations to groups on home maintenance and how to spot potential problems before they become a bigger issue. we take our car to shop to get it serviced and checked and we go to Doctors to get a checkup but most never get a checkup for thir home which can save a lot of money when you catch things early.

  3. Here’s another weird one. Two year old house. Carpet turned black at baseboards and seams. I assumed something wrong with the tape underneath or the cleats at the baseboard. Pulled the carpet up from the baseboards, nothing unusual. Carpet supplier said they’d seen it before & was a bad dye lot that discolored when it was cut so they replaced the carpet. Two months later same discoloration. Brought in carpet factory rep.

    It was a burnt heater coil. Air would cross over the charred heater coil & drop small charred particles on carpet. Vacuum could get to the most of it but not at the baseboards or seams.

  4. Same thing with my plumbing. It was the first house i built in Northamerica. Before that I built homes in Germany and Austria. But a plumbing like in North America i have never seen. Like electricity it is about 50 years behind european standards and quality. I was shocked an inspector came and even aprove such thing where metalstraps attaches a Pipe against a beam. There a Hangers with rubbersleves available and there will be no noise and even easier instalation.
    The pipes are a Industrial standard i can no beleive this one past the year of 1960. Look to europe there a pipes US builders not even have dreamed about it.
    I like your site and hope you help to get this stoneage buildingstandards in USA and Canada to a level of quality.
    Hope there is a strong wind after this recesion throughout the whole building industrie and open us for the existing technology from overseas (don’t like to say this but the whats true is true). Maybe some new companies will pick up and produce quality in USA, but the old companies will (have) go out of business they wan’t change there old stuff.

  5. Thank you for this posting. My wife also suffers from a mild form of Alliumphobia. This winter she has insisted on washing her face in cold water because when she turned on the hot water in our bathroom she started to hear a “drip, drip.” Although I tried to convince her otherwise, she was sure that is was a leak in the hot water line. I needed a back-up to my argument and your blog posting was perfect. It was just how she has been feeling and helped to allay her fears about a possible leak. Now she can happily wash her face in warm water again (and hopefully will have a little more faith in her husband’s opinion next time!)

    • Michael,

      I’m so happy that you (and your wife) found the blog posting helpful. It might also help reassure her to know that I still (after almost 2 years) have no reason to doubt that my plumber was 100% correct, as we have still seen no evidence of leaks. I’ve learned to ignore the sound. :o) Additionally, it is clear to me that this isn’t such a common problem. I know for a fact (via search terms bringing people to my site) that many people are vexed by the same “phantom” leaks sounds.

      Again, this is great feedback and I am so pleased that you found the information helpful!


  6. I recently had a new hot water heater installed. It was high effiency heater in which the plumbers had to install PVC pipe that leads to the outside. Ever since then, I hear what seems to be dripping sounds from above, but there is zero evidence of leaks. What could this be. It is very annoying and bothersome to say the least. Thank you

  7. Same as Jim! I recently started using my heater and hot water in new condo & there’s a hard splat noise. I have PVC pipes too. I’m going to just wear warm clothes & by a heater. I can’t handle this noise and fears.

  8. I have a similar issue but the only difference is that I hear the drip noise after the shower/washer machine is used. Has been driving me crazy but I’m too scared to open up the wall.

  9. This is exactly what I’ve been hearing since the renovation. It also seems to be more of a problem in the winter time than the hot summer months, which now makes perfect sense. I kept bugging my contractor saying there must be a leak! He looked at me and went, where’s the water stain? Lol. Thank you so much for the post!

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