Hayward H400 install question

[sniffmo]

That's part of the problem. I don't have the gauge. But since the old heater was installed professionally and was working properly, can I assume that the gas pressure is acceptable?

[otitis]

With mine, when I installed it, it would not light. The gas co. had to increase my meter pressure and flow, by replacing the meter itself.
Since you already had a heater, you should be OK. I did not.