Water heater flame-out when dryer runs

Installed a new natural gas water heater about 6 months ago. It's one of the new style that has the system that prevents igniting flammable vapors, and it also has one of the high-flow cut-offs that stops the flow of gas when flow is excessive, like if the flex line breaks or whatever.
All was well up until about a month ago. While doing construction on the road out front, my gas line was cut. Not once, but 3 or 4 times (I lost count). (Don't get me started....)
Each time they called the gas co. Repair came out, fixed the line, relit pilot on boiler and water heater. Gas dryer has intermittent pilot.
Now, when SWMBO dries laundry, the pilot on the water heater goes out. Not every single time the dryer flame lights, but it's pretty much certain to go out sometime during each dryer load. The boiler pilot is fine; it doesn't go out at all. During the week when we are not using the dryer, all is fine.
I figure either there is some kind of restriction in the line where it was repaired, or some dirt got into the line and is blocking something. (There is a dirt leg on the gas pipe feeding the water heater.) Not sure how to troubleshoot. I could call the gas company, but that means taking off work and all those hassles.
Any suggestions as to how to troubleshoot this?
TIA,
Paul snipped-for-privacy@hotmail.com
(you know what to leave out)
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Paul Franklin wrote:

1) Fire up the boiler. It will draw far more gas useage than the dryer. See if that affects the heater pilot.
2) Run the dryer in the "No Heat" mode. That will pull air out of the house. See if that affects the heater pilot. (Maybe it's not a gas supply issue...)
Jim
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I agree with Jim. When the dryer is running it acts like an exhaust fan. Typical air flow on a dryer is 50 to 100 CFM. If the house is tight, it may backdraft the water heater flue and blow out the pilot.
Or you may just need the water heater pilot adjusted to a larger flame.
Good luck
Stretch
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And open an window slightly when using the dryer. No matter how large the flame it has the potential to be put out with a strong draft.
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Edwin Pawlowski wrote:

We had a similar problem a few years back. After checking the air flow (mine has plenty of air leaks) we found the gas pressure regulator was set low. We had about quarter pound, needed to be half pound. The gas company finally cranked it up to a half. Then they noticed it was an old mercury regulator and sent the crew a month later to replace it.
TP
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