22 years old is about seven years past time to replace the heater.
Lots of heaters come with only a six or nine year warranty.
Yes, they can sometimes last even longer, but I have seen plenty go out at less than ten or twelve years.
Replace it asap, before it floods and costs you a lot more money.
And it will probably happen on a big holiday weekend, with a house full of guests, and kitchen busy prepping for a party, haha.