A leak from the cylinder body usually means replacement is the sensible route, whereas a leak from a valve, fitting or pipe may be repairable.
For a Cookstown home, cylinder choice should be based on hot-water demand, available space, the boiler or immersion setup and—where an unvented cylinder is being considered—the incoming mains flow and pressure. A cylinder that is simply the same physical size as the old one is not automatically the right replacement.
For the question “Is it worth replacing a very old but non-leaking cylinder in Cookstown”, useful checks include cylinder type and age, recovery time, insulation, hot-water usage, immersion elements, valves and controls, and whether poor performance is actually being caused by low mains flow or another part of the system. If converting to an unvented cylinder, the installation also needs the correct safety components and a suitable discharge arrangement.
Unvented-cylinder work requires the right competence because the safety controls are part of the installation, not optional extras. BMK can assess the cylinder and hot-water arrangement in Cookstown, size the replacement around the household and explain what pipework or control changes are actually required.