How can I slow down the time it takes to shut off the fill in the toilet tank? As soon as the toilet fills, there is a huge bang in the pipes. I heard that there is a product that slows down the shut off and prevents the bang.

See the images below if you tell us which fill valve do you have we will be more than happy to tell you how to fix your problem, Thanks.

John

Hi John,
Thanks for the quick response. Our toilet tank has the first image of the two that you sent (the one that has a yellowish background).
Janet

Hello Janet,

Your fill valve is called the ballcock type see the image below, close the angle valve under the toilet tank remove the screws that I have maked with black dots for you, remove the cap and the rubber seal inspect the seal if it looks bad replace it with a new one, if looks good turn it over and install, check if your problem is resolved if not back to you, good luck.

John

What you are experiencing is called water hammer.

When a fast acting valve such as a toilet or single leaver faucet abruptly stops the flow of water there is a momentary spike in water pressure. That momentary spike causes the pipe to move and bang against a structural member of the house.

If you are on a municipal water system the first thing you should do is check your water pressure. Purchase a pressure gauge such as the one shown below from Home Depot, Lowe's or any hardware store. Screw it on to a outside faucet and open the faucet. Your water pressure should be no more than 60 pounds. If you are on a well system your water pressure will be the cut off pressure of you well pump. Post back if your pressure exceeds 60 pounds.

You should have air chambers or shock absorbers built into you piping system. Air chambers are simply short pieces vertical pipe with the top end capped off. These will be on the piping, inside the walls, near the toilets. Air gets trapped in these air chambers and cushions the spike in water pressure. Shock absorbers are the commercial version of air chambers but have a bladder inside. Over time the air in the air chambered is absorbed by the water and they no longer function as designed. Therefore, you must periodically recharge them.

To recharge the air chambers, turn off the water to the house. Open all faucets including showers and bath tubs and flush all toilets. To drain all of the water in the pipes you must let air in. Air will enter through any two handle faucet. Toilets and single lever faucets do not readily let air in.
After the water has stop draining at your lowest faucet, disconnect the supply tubes from the stop valves of each toilet and each single lever faucet. You will not be able to do any thing at single lever showers and bath tubs. By doing this you will be draining as much water from the pipes as possible and letting in as much air as possible.

After all of the water has drain from the pipes, reconnect the supply tubes to the stop valves. Double check to make sure that you have reconnected all that you took loose. Close all faucets. Turn the water to the house back on. Open the main shut off valve slowly. If you open a main valve too quickly you can blow out the cartridge of single lever faucets.

The air in the pipes will be forced into the air chambers and be trapped there. Your air chambers will now absorb the spike in water pressure when the toilet shuts off.

PS
If you are not comfortable disconnecting the supply lines, just turn off the water, open all faucets and wait several hours before turning the water back on. Enough air should find its way in to let the air chambers drain.