Hello. Desperately need your help. I live in a newer home (less than 1 year old). For the past month, I am hearing a banging noise in the floor between my first floor and my basement when I flush any toilet in my house. It started as a faint noise but now its fairly loud. I can now hear the bangs in the pipes every now and again with no flush, and this is happening in different areas. I have tried to self-diagnose the issue. I have bled the water system, turning off the main shutoff and turning on all the faucets, etc a few times now. It seems to help but just for a few hours. Any ideas as to what might be happening?

Thanks,

Keith

If the banging only happened at the end of the toilet filling its tank when the water to the toilet shuts off suddenly then it would be a classic water hammer problem. Are you saying the banging also happens at other times but you can't attribute the noise to any water usage?

Since the house is new, less than 1 year old, are you under any homeowner's warranty? If so I'd check with the contractor or the home warranty folks about having the plumbing checked.

Do you know what your water pressure is? Do you have a lawn water sprinkler system that runs automatically? Is your water supply from a well or from a city municipal water supply?



Edited 6 times.

Thanks for your note. The banging certainly happens towards the end of the water filling. About 20 minutes after the last time I flushed the toilet, I heard another bang in the floor and I can't attribute that noise to any water usage. This happens randomly at different time during the day. I also thought it was water hammer but I've tried draining the system 2 or 3 times now and it only seems to work for an hour or so, then back to the banging. Any other ideas?

I don't know what my water pressure is. I don't have an underground sprinkler system either. My water is supplied from the village.

I had the contractor over today and he couldn't immediately identify the cause. He is going to check with other plumbing experts and try to remedy.



Edited 1 times.

A quick check of your water pressure would be a good first step in determining the problem.

48 psi. I think that is well within the range. Any other thoughts?

What about the home warranty question, do you have it? If so press the builder or home warranty folks to figure out what is going on, you shouldn't have to.

Water pressure of 48psi is not considered high pressure, in fact some would say it is on the low side but still adequate.

Because the noise is usually related to water usage you believe it is water pipe and not something else like ductwork or the furnace for example that is making the noise? Does the noise always seem to come from the same general area (below you) or from varied locations? If you shutoff the master water shutoff valve for an hour or two then you wouldn't hear any of these noises?? (you can still use and flush a toilet with the water shutoff, the tank will give you one flush).

What type of water pipe does you home have (pvc, pex, copper, etc)?



Edited 5 times.

It's the ball cock in the toilet or a partially closed shut-off valve.Also check for a flapper leaking threw.



Edited 1 times.

I have seen abs waste pipe pop when hot water is flushed through the drain. The pipe expands when heated. That is why it is important to isolate abs from touching any wood and make sure that there is room for expansion from heated water being flushed down the pipes. But you indicate this is a water closet so hot water is not piped to these fixtures, normally. There are Bidets and Bidet Seats that get hot water but I don't think that is what you describe. Good luck.

I think NoHub got it. Check toilet fill valves & flappers

StuckinLodi....thanks for your comments. Here are my notes:

I do have the home warranty. Builder came over to inspect but was stumped. Said he needs to talk to other experts to figure out what it might be. I'll keep pressing him.

The noise always seems to come from the same general area. It is a consistent bang...can happen once or 6 or 7 times. There are more bangs when the toilets haven't been used for a longer period of time (overnight).

I don't know for sure if the bang is coming from the water pipes or something else but the banging seems to happen only when we flush the toilets. Do you suggest shutting off the main water supply and then try to flush the toilet and see what happens?

I believe the piping is copper.

Yes to shutting off the water in the whole house and then flush the toilet, see if the noise occurs. You may have to try this a few times to get reliable results. If the bang still happens you will know it probably isn't due to water flowing in the pressurized piping or to the fill valve inside the toilet, that maybe it is in a drain line. If the noise never happens with the whole house water shutoff then you could have something going on with a pressure water pipe. Since the noise seems to be triggered by flushing you will need to do this for each toilet you have, shut off all the toilet shutoff valves except the toilet you are testing with.

Also, most water heater installations have a shutoff valve on the cold side, you can try shutting it off for this noise testing. Is your water heater elec or gas? Could the noise be happening when the water heater comes on to heat the water?

The best theory at this point seems like it is maybe a noisy toilet shutoff valve below the toilet tank, or a bad fill valve inside the toilet tank. You can make sure the toilet shutoff valve is adjusted all the way open for max water flow to the tank, but if it already is set that way then try turning it down some, maybe find a happy point if that is what's causing the noise. If you have more than one bathroom you can shutoff all the toilets except for one, if the noise goes away you will know it is something you shut off. Try to figure out where the noise is coming from by isolating and eliminating possibilities. Your fridge may have an icemaker, you can lift the bail on it to shut it off just in case that's it. If you have a water softener then disable it and activate the bypass that shunts water around it. Keep shutting off stuff, when the noise goes away whatever was among the last things you messed with is likely where the problem is.

If your basement is not finished you should be able to see most of the plumbing drains and pressure water pipes (hot and cold). Look for anything odd, bent out of position, unsupported pipes, etc. Look for pipes that might be under a strain that suddenly slip with water flows thru them or 2 pipes against each other, especially the water pipes that go to the bathroom.

You can have someone flush the toilet while you are in the basement so you can feel the drain pipes and the pressure pipes to see if you can determine anything when the noise happens.



Edited 8 times.

Thanks stuckinlodi. A few updates:

I shut the water off to the whole house and flushed the toilet. I still get the banging sound when water is pulled in to fill the toilet. After a few flushes, the banging is no longer there but there isn’t water going to fill the toilet any longer. Therefore, I think the banging is in the pressurized piping.

I also tried shutting off the shutoff valve on the cold side of the water heater but the bang was still there when I flushed the toilet.

My water heater is electric. I have two of them.

All of my toilet shutoff valves were open all the way. I closed each one a bit and the bang went away for a bit, but unfortunately it returned after I waited for a few hours to flush the toilet again. Also, during all this testing and research, I noticed that I also get a random bang when I am not flushing any toilets. Do you think this means something different?

I haven’t tried any more process of elimination yet. I’ll keep playing around to see if I come up with something.

Unfortunately my basement is finished so I am unable to see the pipes. While I’d prefer to solve this from a non-invasive approach, I feel that I may need to open up with ceiling/walls to see what is going on.

Author: kradeke (IL)

"I shut the water off to the whole house and flushed the toilet. I still get the banging sound when water is pulled in to fill the toilet. After a few flushes, the banging is no longer there but there isn’t water going to fill the toilet any longer. Therefore, I think the banging is in the pressurized piping."

-----------------------------------------------------------------------------------------------------------------------

Not quite understanding this part. If the whole house water was shutoff how did the toilet have water filling the tank? Do you have a boost pump with a reservoir tank or something holding water pressure even when the entire house water is shutoff? Is this a normal single-family home, or a maybe a duplex or condo unit or something we aren't taking into account? Something has to account for the toilet getting water to refill its tank for several flushes even after the whole house water is shut off??



Edited 13 times.

I have a normal single family home. I turned off the main water supply and was still able to flush a toilet a few times before the water stopped filling the toilet. I don't believe I have a boost pump or reservoir tank. Is it possible that an arrestor or air cushion device that they would have installed has gone bad? Still very confused and frustrated with this.

I'm confused also, don't know what's going on with that. From what I know when you turn off the main house water shutoff valve you lose all water pressure, no new water can enter the home piping system. There will be some residual water pressure in your pipes at first but it is rapidly dissipated as soon as any faucet is turned on or the toilet is flushed. Can't see how you could flush the toilet several times when the whole house water shutoff valve is closed. Are you sure you closed it completely? (don't wreck the valve by over-tightening or applying too much force).

If you had a reservoir tank or a boost pump or a water softener you would have seen it if you've lived there a while. A water hammer device like an arrestor or air cushion can go bad or become ineffective but it then just becomes a dead end pipe, wouldn't cause your toilet to be able to flush several times with the whole house water shutoff.

This is odd to me, I don't know if it is related to your noise problem. Maybe other experienced plumbers can see what is happening. In the meantime I'd keep pressing the builder/contractor to find out what is the problem. He's the one that should fix it even if you get it figured out since you have the home warranty. Sometimes a problem is much harder to figure out over the internet instead of being there in person.



Edited 2 times.

Do you have a septic system or a sewage ejector pit?

I have a sewer ejector pit

May not be your water lines. Could be the check valve slamming shut