Welcome to Plbg.com
Thank you to all the plumbing professionals who offer their advice and expertise

Over 696,600 strictly plumbing related posts

Plumbing education, information, advice, help and suggestions are provided by some of the most experienced plumbers who wish to "give back" to society. Since 1996 we have been the best online (strictly) PLUMBING advice site. If you have questions about plumbing, toilets, sinks, faucets, drains, sewers, water filters, venting, water heating, showers, pumps, and other strictly PLUMBING related issues then you've come to the right place. Please refrain from asking or discussing legal questions, or pricing, or where to purchase products, or any business issues, or for contractor referrals, or any other questions or issues not specifically related to plumbing. Keep all posts positive and absolutely no advertising. Our site is completely free, without ads or pop-ups and we don't tract you. We absolutely do not sell your personal information. We are made possible by:  

Post New
Log In
How to Show Images
Newest Subjects
 Thumping Noise Coming through Drains and/or Toilet
Author: dtaraboletti (FL)

I recently completed a bathroom remodeling project. During the course of the project, I started to notice a thumping noise coming from the drains (and/or toilet). The thumping sound sounds like the opening to Law & Order (https://youtu.be/gP3MuUTmXNk?si=uGn7OwV-zY70cm_d). It always occurs in pairs (2 thumps). I presumed, during the course of the project, that this may be related to the traps being dry...but now that the project is done and the traps have water, the thumps are still happening.

It does not seem to occur with use of the plumbing (like running the faucets, flushing toilet, etc). It is not a Knocking sound like would be typical of a pipe banging against the studs or an in balance of water pressure. It also does not appear to be related to temperature differences in the pipes as it occurs at all times of day.

I know it sounds crazy, but the thumps seem to occur whenever someone drives past the house (and perhaps over the manhole cover on the road immediately in front of my house). I realize that the storm sewer is not connected to the waste water lines, but that is the only consistent cause/effect that I can surmise.

Any thoughts on why this is happening or how to troubleshoot it? It's only been a week since we finished the project and it's already driving my family crazy.

My plumber has no idea what is causing it.

Thanks in advance for your input.

Post Reply

 Re: Thumping Noise Coming through Drains and/or Toilet
Author: steve (CA)

As soon as I started reading your post, my thought went to cars running over manhole cover. If the traps are holding water as they should, the noise would be coming from some other opening to the sewer system. If the toilet wax ring is not sealed correctly or a vent pipe not connected and ran through he roof, these could allow the sound to enter the house.

Post Reply

 Re: Thumping Noise Coming through Drains and/or Toilet
Author: dtaraboletti (FL)

Thanks Steve. I ran a test and determined that the manhole cover is for sanitary (NOT storm) sewer... so the sound could be transferred into the home. Also, confirmed that cars running over the manhole cover is 100% correlated to the thumping sound and the spacing between the two thumps is consistent with front/back tires crossing the manhole cover. All traps are now filled with water which has reduced the sound levels...but still coming through. I will check the wax seal today.

Post Reply

Please note:
  • Inappropriate messages or blatant advertising will be deleted. We cannot be held responsible for bad or inadequate advice.
  • Plbg.com has no control over external content that may be linked to from messages posted here. Please follow external links with caution.
  • Plbg.com is strictly for the exchange of plumbing related advice and NOT to ask about pricing/costs, nor where to find a product (try Google), nor how to operate or promote a business, nor for ethics (law) and the like questions.
  • Plbg.com is also not a place to ask radiant heating (try HeatingHelp.com), electrical or even general construction type questions. We are exclusively for plumbing questions.

Search for plumbing parts on our sponsor's site:

Special thanks to our sponsor:

Copyright© 2023 Plbg.com. All Rights Reserved.