Some solar cylinders fail due to corrosion. The solar probe pockets are particularly susceptible to this problem. However, these can often be sealed off.
Alternatives to cylinder replacements
If the main solar coil has perforated, it is often possible to fit a separate heat exchanger.
Solar cylinder replacement
If the actual cylinder needs to be replaced, we will often recommend to increase the size to avoid future overheating.
The new solar cylinder is likely to be better insulated and have a more efficient solar coil than the old one.