Sorry to hear that ... we too have had a few of those burst geyser experiences of recent, as clearly geysers don't like the intermittent water and power supply currently the norm in SA .... I now have the belt an braces approach with pressure regulation, anti backflow valve and (air),pressure release on the water main coming into the house as well as on the individual geysers.
Plumber gave me the same rundown, going to add a new pressure valve by the geyser (already got one on the mains coming in), non-return valve will be replaced, air pressure release will be replaced. The one that popped lasted us about 5 years (had a 3 year warranty on it), so it was bound to give in with the recent issues we had up and down our main road with water leaks and pressure changes.