I just replaced the flush valve seal in the toilet. When the water is running the pipes make a drilling sound. It happens a about a minute long.

Hi Lundy

First, close and then reopen the toilet shutoff... see if that resolves the issue. If the issue is not resolved, then remove the replacement seal and put a towel over the fill valve, pulse the water on and then replace the seal again... see if that resolves the issue.

If all that fails to resolve the issue then the toilet shut off valve itself may have a loose washer that is defective/loose and will need to be replaced. Here, shutting off the main water supply to the house will probably be required... ;)

Try the simple stuff first!

Mark