Hayward H200 wont light.

[Poconos]

Are you sure it isn't just air in the line that has to be bled out? I have an H250 that hasn't been used in years and as I recall, at spring lightup, I would wedge a stick on the button you hold down to light the pilot because I didn't feel like sitting there waiting. I'd just come back 15 minutes or so later and light the thing. The gas flow for just the pilot is so low it could take many minutes to bleed the air out of a long line.
There should be no explosion issue if the heater is ventilated properly. If you're concerned about that, let it bleed a while, then release that button for a few minutes to let any accumulated gas to disperse, then try and light it normally.
If this isn't the problem we'll work it more.
Al