It's good to hear that the direct cause of the failure is now known. Nonetheless, it certainly doesn't hurt for everybody to still be reminded that the best safety is due diligence and caution around any "live" system.
basically PVC should be realatively safe there are ups and downs for every material type. cooper or steel accumulators may only ever fail once but at the pressure that contains it will fail with much worse consiquences. eg death to anyone in a 2m radius. as you can see above disregarding degredation the accumulator probubly exploded at 1500psi. any material will under constant fluctuation have stresses introduced this will eventually cause failure the best way to avoid this sort of failure is monitoring them, if your pvc has hairline strech marks or discolouring replace it, treat them well do not leave them in the sun or pressurised and they will last a number of years. alternatively a pressure failure point should be used when joining to the accumulator. place a length of pipe that fails at 110PSI before the accumulator. this having less pressure and less mass will have less safety risks.
