The flexible water line connected to the bottom of the commode tank vibrates when the commode is being fill?

Question

The flexible metal water supply hose connected to the bottom of the commode tank vibrates ( noiselessly ) at a high speed only when the tank is being filled after a flush. I discovered this when I was feeling the hose for possible moisture because the plumber had had to replace the first hose he installed because it leaked. and I wanted to make sure the second one was not leaking. Both water supply hoses he installed under the basin also leaked, flooding the bathroom for several hours. He said all three hoses were defective. The plumbing company has stated that they will be good for whatever repairs are necessary ( three bids necessary). Another clue concerning the vibration: the hose to the other commode tank also vibrates. The second commode has worked OK for eight years. My concern is that the vibration will, over time, loosen the connection to the tank and cause leakage. This is not "water hammer"; there is no noise. Does anyone have the answer?

Answer 1

This is due to the velocity of the water through corrugated tubing.

Slow the flow down or use a connector that is not corrugated.

Answer 2

This IS "water hammer", whether it makes a noise or not.. It is caused by either air being in the water system, high water pressure, or something being loose in the system (like the washer in the stop going to the toilet supply). It will be felt in the supply line because that is the area with least support and the most flex.

If  you have had the plumbing worked on recently, air could have been introduced into the lines. It will eventually work its way out.

If it is from high pressure, a number of different combinations could cause your symptoms. A loose washer in the stop going to the closet supply could be vibrating. If you changed the ballcock valve from a water displacement type (rod and float) to a positive shut off type (fluidmaster), the action against the new washer will cause a quick start stop action that causes vibration. There may be an adjustment s***w on the ballcock valve that will minimize or stop  the vibration.

Turn the cold water on in the lavatory faucet or tub while flushing the toilet. If the vibration stops, it is a pressure problem. If you have a pressure regulator, reduce the pressure by turning the set s***w a couple of rounds.

It also could mean that the regulator is going bad.

Pressure problems usually show up first in ballcock valves, and eventually in solenoid valves in the dishwasher, washing machine or ice maker.

At worst, a  new regulator and a pressure expansion tank can be installed in the water system to alleviate the problem