I put a new gas valve in my water heater but now the pilot won't light. I must have gotten some crud in the jet when I had the lines disconnected. I have a set of small drills for cleaning welding torch tips but before I go drilling into the jet I'm wondering if any of you know what size the hole in the pilot light jet for a natural gas water heater is? Engineman
Normally, the tubing from valve to pilot light needs to fill with NG. This takes time to purge the air out of the pilot light tube. Do you see deflection in the match flame when you have the 'pilot' button depressed? That's air, not NG. Be patient, it'll light.
If you don't see deflection in the match flame, then you get to troubleshoot.
In addition what the other guys said about bleeding air out and cleaning the jet, some, but not all, units have an adjustment for pilot flame size. The original water heater docs should have details if so equipped. We usually stuck one of those big manila envelopes on the side and stuck in the directions. I know I had to bleed my new replacement heater for what seemed like hours before it lit off, was probably more like 15 or 20 minutes I leaned on the valve in "light" position before it finally went. There's not a lot of gas passing through that jet per minute, after all. I had probably 20 feet of pipe to clear to the meter shutoff, too.
For orifice cleaning, I use either the 61-80 number drill set or a gas welding tip cleaner set. Just pick one that fits and don't try to drill things out. You might tape a narrow strip of tissue paper to a stick and see if there's anything passing through the jet. A squirt of bubble solution might work for that, too. If you haven't done that to your pipe joints, you might do that before putting things into service. Nothing like a slow gas leak to ruin your day.
One of my nice neighbors let me connect my plumbing to their hose bib for a few hours so I could flush toilets and wash hands while replacing the pipe to my water meter.
The first time I connected, *hot* water came out of the 'cold' water tap! I was chagrined to discover that I had connected the hose to the wrong valve and was back flushing the water heater into it's supply line.