Toilet water hammer after new fill valve

[sodani]

I recently replaced my leaky toilet fill valve (Fluidmaster 400CRP14) with a new one. Then when I flushed, I get water hammer that vibrates the pipes. If I close the valve that goes from the wall to the toilet so that it's open only 1/4 turn, then the water hammer goes away. However, it takes a long time for the tank to fill. I also tried clearing any air from the pipes but my efforts had no effect. Any ideas would be much appreciated.

 

[Geofd]

It's possible that your washer on the stop is floating, usually they are simple push on washers, easy to replace

 

[sodani]

It's possible that your washer on the stop is floating, usually they are simple push on washers, easy to replace

The stop you're referring to is the toilet shut-off valve?

 

[Geofd]

Yes, if it's marked brass craft there are 2 washers that you change, you can also change but the same valve and change the stem that's were I would start, just make sure if the old washer has deteriorated that you look inside the pipe to get it all out