Hello, so the toilet in my bathroom (in the master) started making a loud banging noise after I flush and as the water is going down, it sounds like the noise is coming from the pipe in the wall. This happened a couple months back and I used a plunger and the noise went away and is now back. I tried the plunger again but the noise stayed this time. My house is about 10 years old and the toilet is on the upper floor. A friend said that it is water hammer and I shouldn't worry about it?
Thank you

Yur friend's mistaken. Water hammer happens in the water lines not the drainage system. Describe the noise. Thump? Bang? Do you feel a vibration when it happens? How long from the time you flush do you hear the noise?

All good questions, I'll post later after I get home. Thanks

The noise has actually got better since I posted but you can still hear a bang type noise, it almost sounds like the water going down the pipe very loudly but it has never done this before. No vibration and the noise occurs right as I flush and as the water is going down.

Bump

Yep, not water hammer. Water hammer is generally one big thump when the tank reaches its full point. Is this a gravity toilet or a pressure assist?

No idea, how could I determine that?

A pressure assist toilet will have plastic tank inside the porcelain tank, about the size of a football, usually blue.

What material are your drainage pipes made of? Cast iron? Plastic? Is there any actioin in the bowl when this happens? Tom

I'm pretty sure it's a gravity.

Plastic pipes. I think you are asking if anything happens in the bowl when I flush? If so, nothing irregular happens, I flush and the water swirls down regularly but as this is happening the banging in the pipes is also occurring.

Gravity feed is pretty much flapper, fill valve and overflow pipe, simple compared to a pressue assist. Now go back and answer Tom's questions. I'm getting lost and he is not.

Any other advice on this? I'm thinking about calling the plumber but would rather not drop a hundred for a house call...

Tom will probably be back here soon. The only thought that comes to my mind is that the 4" PVC drain may not be secrure. It can bounce when the flush starts, especially when the water hits a turn. Don't know other than that.

Bump

A plastic drain not secured properly can "bump" againist a wall stud or framing member. Can you reach this pipe at all?

May have something obstruting you vent on the roof or where the drain line vents. Are you in a wooded area with critters, leaves, etc. Is the noise a "pluugg..pluugg" sound more than a "bump"?