Plumbing and Piping - Pipe has a loud "bang" when toilet shuts off

The tank ball/flapper assembly was replaced with one of the newer cup-types (not sure what that's called, sorry!). Now the toilet works fine, but at the moment the toilet shuts off, there's a loud bang in the pipe in the wall, that you can hear through the whole house! Is the pressure too high going to the toilet since that assembly was changed? There's a valve between the tank and the wall, that I assume is the shutoff valve, do I need to adjust that, and if so, clockwise or counterclockwise? I adjusted it a small amount one time (I forget which direction now), and the toilet shut off quietly, ONE TIME! Now it's just as loud as ever. Thanks for your help.

Dawn :)

What that's called is water hammer caused by a loose pipe in the wall banging against framing when the water flow is abruptly shut-off by the toilet tank water inlet valve.
You can try reducing the water pressure to the tank by turning the shut-off valve handle a bit clockwise (to right) to close it slightly. This also cause the tank to fill a little slower, but that's O.K.
If that doesn't work, you may need to install a water hammer arrester on the pipe just behind the shut-off valve.
Good Luck!
Mike

Just a note on water hammer, it is not caused by a loose pipe in the wall. It is caused by the fact that water doesn't compress like air does. So when you have water running through the pipe at high velocity and it is abruptly shutt off the water still wants to travel at velocity. Since the water cannot compress and there is no where for tha water to go it "hammers" within the pipe. An air chamber or hammer arrestor absorbes the shock at the fixture. Sometimes the loud bang can be caused by the ballcock. If it is a new problem you might rebuild or replace the ballcock. Sometimes the air chamber fills with water, nullifying its effect. Draining the system and recharching it can fix that problem. water hammer usually only happens when you have a long run of straight pipe as it won't happen in short runs and having elbows in the run helps to absorb the pressure over lenth.

Thank you for the fast responses! :) I will try adjusting the shutoff valve again, and will install the water hammer arrester if needed, assuming that's something I can handle doing! ;)

I noticed it happens (although not quite as loudly) when I use the sink faucets in that same bathroom, so the poster who mentioned the long pipe is probably right about that, since this doesn't happen with the other sinks or bathroom at the other end of the house.

Thanks again!
Dawn :)

try putting in a fluidmaster ballcock, a cheap fix. The ballcock often causes this type of problem.