Plumbing in the Home/Water Pipe Howling


I recently replaced a water heater and I was talking to the installer while he installed it. I noticed that when he cut the copper pipes for the intake and outflow on the new install, he did not ream the inside copper pipe (smooth the lip that forms) when the pipe is cut on the inside. He did of course brush the outside with emery cloth. Having done my own basements only, I am no expert and figured it would be ok, but I should have said something. Is it possible that the lip in the pipe in my basement is causing enough friction that it could be causing the howl to be heard 20 feet away in our master shower? All I know is once we replaced the water heater the howl started immediately. That was the only change as we did not mess with pressure, etc. The only other thing it could be is the water heater itself. I will say that the howl is very annoying. Any ideas?

Hello Randy,
If the ridge is left inside of the copper pipe after cutting (against code) it creates a phenomenon called cavitation when the water flows across it. Essentially the sudden micro-pressure drop causes tiny air bubbles in the water flow and these can eventually erode the interior of the pipe causing leaks. I haven't heard that they cause any kind of noise issues but I suppose it's possible.

Another thing to look at is that some water heaters come with it backflow device installed on the cold water pipe nipple. Essentially it is a check valve that prevents the hot water at the top of the tank from rising up into the cold water piping by convection. This is also something that could potentially cause some noise during high flow conditions.


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Dana Bostick


Pretty much any residential plumbing questions. For "item specific" details such as a specific model of fixture, I will need to research and there may not be any useful information available. Note: I live and work in Southern California. We do not, as a rule, use hot water or steam heating systems, oil fired boilers or private water wells so my knowledge in those areas is pretty limited. There are others here on AllExerts that can probably answer those questions better.


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