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Pipe layoutJust converted a wood burning fireplace to a natural gas one and there is a jet engine sound when opening the valve and lighting the burner. We tied into my existing 2" line coming into the house with 1/2" pipe. There is about 5' of 1/2 inch pipe from where we tied in to the burner. It is not the whistling sound some describe as being associated with flex pipe. There is a 12" piece of flex from the control valve to the burner. After adding a regulator which is set at 3.5"WC we had the local gas company check and confirm pressure from the meter is 7"WC and the meter is operating as it should. The regulator seemed to reduce the noise slightly but did not eliminate. The only time you do not hear the noise is when the valve is open fully...anything less and you can hear it. Removed the burner and lit just the end of the flex pipe and you still hear the noise. Two plumbers later and a visit from the gas company and no one knows. Any ideas of what might be causing the noise?

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    Martin your question is really hard to follow - you might want to edit your question with first the problem and then describe the lines - a picture created with a paint program or something of that nature would give an easier to understand description of what you have. The noise is most likely eddies in the line which is kind of a turbulence - I am guessing here that your regulator valve should be at the 2 inch to 1/2 inch - but that is a guess. – Ken Nov 29 '17 at 1:59
  • Thanks for the input Ken...not much with drawing software but hope this will help. – Martin Nov 29 '17 at 2:33
  • Yes that helps a lot. I am guessing here that the position of your regulator is the cause of the noise - I would move it close to your gas valve that way I have full incoming pressure backed up in my 1/2 almost all the way to the gas valve (you stated when your valve is full open the noise is gone - so it seems that low pressure between regulator and and valve is causing the issue). You don't have a strainer for that regulator in there either .. you should install one if you want it to work for a long time. – Ken Nov 29 '17 at 3:24
  • Ken, don't physically have enough space to move regulator any closer to key valve as at the first 90 degree elbow after the regulator the pipe goes into the wall and runs about 24" before it hits the valve....that 24" space is the stud wall, space between wall and insert then the air space between insert and fire brick. Lastly the noise was present before installing the regulator.....after installing the regulator there was minimal difference in the noise. Thanks – Martin Nov 29 '17 at 4:45
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The flex pipe is making the noise, I had a big gas furnace in my shop that I used a flex pipe, oh my it would whistle, upsize6 to 3/4" and the noise was way less. Added is on simple fibreglass insulation around the flex and my bat ear kid said it was ok.

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