How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site. Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask Patrick Your Own Question
Patrick, General Contractor
Category: Plumbing
Satisfied Customers: 2429
Experience:  30 years commercial construction and 23 years house remodeling projects
Type Your Plumbing Question Here...
Patrick is online now
A new question is answered every 9 seconds

I have a humming noise come from inside a wall in my bathroom.

Customer Question

I have a humming noise come from inside a wall in my bathroom. If I put my ear to the wall, I can hear a "clunk" sound right before the humming (like a loose pipe or slight water hammer). I have tried to isolate the fixture that is causing the sound, including toilets, sinks, bathtub, etc. However, the sound remains when supply is cut to these fixtures. In fact, I cut the water supply to the house and cleared all of the lines and the sound was still there even when there was no water in the lines. So, it may not be in my plumbing system. I also have hydronic/hot water heat, so I supposed there could be air in those lines. However, I ran the system last night to move water around, and I bled the baseboard radiator that is close to where the noise is coming from, and the noise is still there. Any thoughts?
Submitted: 8 years ago.
Category: Plumbing
Expert:  Patrick replied 8 years ago.
Do you have a vent pipe in this wall? Is it clear at the roof?
Customer: replied 8 years ago.
I'm not sure. Are vent pipes associated with the drainage system off of sinks? The hydronic heating/boiler vents through a chimney. How can I check for a vent pipe?

It might make sense that something in the drain system is wrong. We recently had some sinks replaced, and the drain pipes heading into the wall were exposed for a couple of days in two spots. When those drain pipes were exposed is when I started hearing the noise. But all plumbing work that was done was external to the wall for the most part.
Expert:  Patrick replied 8 years ago.
The sinks, showers and toilets typically have a vent pipe that will rise out of the top of the wall in the attic and penetrate through the roof. Sometimes they will bring them together and bring them up as one penetration. If work was done when they were working on your drains and did not fasten everything back and strap it off, you could be getting some vibration or movement. This should go away if you had the water drained as you did. Do you have high water pressure in your area?
Customer: replied 8 years ago.
As far as the work that was done, it was just removing drain traps under the sinks and then replacing them (we had countertops removed/replaced and new sinks installed). So, there wasn't anything that needed to be strapped, etc. I don't know if we have high pressure, but I've lived in the house 5 years and never heard the sound until about 2 weeks ago. A couple questions:

1) If I cut the water supply to the house and emptied all water from the lines, and the sound is still there, doesn't that eliminate the high pressure concern? Wouldn't that also eliminate concerns about toilet fill valves and bad washers on faucets since no water is moving through the system?

2) If a vent pipe is partially clogged, could that result in a vibrating or humming sound as air moves past the obstruction?

I'm thinking this might be air in the hydronic system, and will probably completely empty that tonight when I get home.
Expert:  Patrick replied 8 years ago.
The answer to No. 1 is yes. You relieved the pressure and with no water in it there should be no noise. As for #2, unless you live in an area of high wind I just cannot believe that you would get ongoing vibration. As for hydronic piping, you need to bleed the highest and farthest away point in the system and do each radiator to remove all of the air. I looked back at your comment that you had bled the one radiator. Add water and bleed all of them. Good luck. If this has proven helpful, please remember to hit ACCEPT, otherwise I do not receive credit. Thank you.
Customer: replied 8 years ago.
I don't think this completely answers my question, just serves to narrow my focus on where the sound might be coming from. I've bled the you know how to purge air from a closed loop hydronic heating system? I think that's the next step I need to take.
Expert:  Patrick replied 8 years ago.
I am including a detail of both draining down, refilling and purging that should apply to your system: <br />Ok, for the system, you should turn it off so that it is not heating. That means shutting it off electrically and at the gas valve. Let it cool down so that you do not scald yourself. At the lowest piping point of your system you should have a drain valve, like a hose bibb. This is were you would connect a hose and put the other end somewhere where you can let the water drain off safely without damaging anything. Keep the hose down low so that it can drain. Open the valve that the hose is connected to and then go to your highest radiator / and farthest from the boiler and open the bleed valves on the radiator. You should hear air being sucked into the bleed valve as the water should be flowing out of the end of the hose. Do this at each radiator bleed valve. When air quits being sucked in the water should quite flowing from the hose. The system is empty. Now, shut the valve that the hose is connected to and shut the bleed valves on the radiators. Connect your fill hose to the system, unless your system is piped directly (not common). The fill valve is usually under the boiler. Now turn on the water and begin filling your system back up. Go to you lowest radiator and open your bleed valve and let the air out. When the air stops bleeding out shut it and go to the next radiator. The idea is to bleed the air off as the system fills. Run your pump ( you may not have one depending upon your system) and bleed the system off again of any left over air. Turn off and disconnect the fill loop. You may need to repeat this procedure again until water runs clean from the hose. Depending upon how hard your water is this should be done at a minimum of once a year. As to your domestic hat water piping, you should check on any drain valves from the secondary heat exchanger and perform the same flushing procedure. Drain the tank and let cold water flow through it to flush sediments out. Again, you may need to repeat the process.You may have trouble with the diverter valve (Not applicable to your system if it is for heating only and not domestic hot water.). It may be clogged or not operating properly. If your system has not been maintained for a while you a may need technician called in to treat and flush your system. This would be a chemical/power flush. Leave this to a professional. I hope this gives you some ideas. Remember, turn the boiler off and allow it to cool. Always remember to close valves so that you do not flood your house. Turn off your fill valve and disconnect the hose. Good luck. If this has proven helpful, please remember to hit ACCEPT, otherwise I do not receive credit. Thank you. <br />Expert of the Month <br />Picture
Expert:  Patrick replied 8 years ago.
Customer Just seeing if the information I sent helped with draining, refilling and bleeding off air in your system?
Customer: replied 8 years ago.
That's helpful, yes. One last question before I accept: I have four separate loops in my system. Should I empty and refill them all at the same time, or should I do one loop at a time? Should I also empty the bladder tank? By the way, I do have a system with the supply coming straight from the main water supply (no need to connect a supply hose to refill).

Expert:  Patrick replied 8 years ago.
If you can do each loop individually you may have more control at isolating the problem. As for the bladder tank, if you can confirm that it is operating properly my thought would be to leave it alone. Good luck.
Patrick and other Plumbing Specialists are ready to help you
Customer: replied 8 years ago.
Thanks for the help.
Expert:  Patrick replied 8 years ago.
Good luck with your project.