Do you have a cracked radiator ?
Receiving a cracked radiator is extremley rare. Most radiators in mainland Britain are steel, there are some aluminium and historically cast iron but in the majority radiators in domestic houses are steel. These come in the form of pressed steel panel or tubular steel in the form of column radiators or towel rails.
The production of all radiators is now highly automated and the end result is an extremely well tested and manufactured product. In previous years there where definitely inconsistencies with production but pretty much all manufacturers have established that it is better just to spend a bit more time on the product rather than detrimental to the brand or paying out for compensation.
So the frequency of leakers and badly produced radiators is very, very small and well under 1% in most cases. This is a down to quality products being used from the outset with stringent testing throughout the production. Unfortunately this does not stop inadequate protection being undertaken after the radiator has been installed and any active contaminates in the system really corroding the radiator out very quickly.
Correct dosing of the system is also very important when using column radiators and towel rails as they are tubular and hold a lot more water. The rule of thumb is that most chemical inhibitors dose 100 litres of water or up to 10 radiators. This does not take into account tubular radiators and systems with 10 column radiators on can hold up 400 litres of water.
Cracks in the radiator are as established, not generally there before installation, unless there is transit or handling damage, so this means that crack or holes generally occur due to corrosion. The problem with corrosion in one radiator can signal a really bad system and it may spread to more than one unless you do something about it.
In order to establish if you have a crack in your radiator is actually pretty easy as it will start to leak water or bubble the paint work. The bubbling and discoloration of paintwork is a firm indicator that the corrosion or rust is happening from the inside out. Surface rust or outside in rust is spotted and it can lead to a hole or crack but obviously hopefully it will take some time to occur if the internal system is protected.
The internal water system is always fluctuating in heat and if there is a real presence of oxygen then corrosion can occur very quickly.
No-one likes cracks in their radiators but it does happen over time and all you need to do is isolate the radiator valves and maybe use an external leak sealer.