The problems with installing a new cistern on an old pan are 3 things:
Firstly, older toilet suites, especially those older than 5 years, were designed to clear solid waste with 9-12 litres of water, while new water efficient toilets are designed to clear with only 4.5-6 litres of water. By fitting a lower capacity water saving cistern to an old pan you will have a big problem with solids not flushing away, thus having to flush the toilet several times.
Secondly, many people these days are choosing a close coupled or wall faced style suite, these types of suites have the cistern moulded so it fits snuggly onto the pan it matches. It cannot be fitted to any other pan. The only way you could change the cistern would be if you have an existing connector/ link suite.
Thirdly, Cost. To purchase a cistern on its own can be quite expensive, most manufacturers prefer to sell a whole complete toilet suite, rather than sell the components separately, therefore some cisterns on their own can almost be the same price as the whole suite.
RELATED ARTICLES