The cold water storage cistern is at the heart of any cold water plumbing installation but did you know that you can actually find different types of cisterns in a property? The central heating system will have a so called feed-and-expansion cistern and you can also find individual cisterns for WCs in a property. When it comes to cold water cisterns, there are basically three main ones available; galvanised iron cisterns, flexible plastic cisterns and rigid plastic cisterns. In this article I will tell you a bit more about these.
Galvanised Iron Cisterns
These are the type of cisterns traditionally used for cold water plumbing but by using iron, it means they are not only heavy and expensive but will also suffer from corrosion after a while. If you come across one of these and if it show signs of age and is badly corroded, please replace it to a modern version, using one made of either flexible or rigid plastic.
Flexible Plastic Cisterns
The great thing about flexible plastic cisterns is that they are circular and can easily be squeezed through tight loft hatches thanks to their flexibility. This means they are easy to work with but also that they are too light to support any pipework and the cistern can actually split if you put too much weight on it. This means that pipework will have to be supported in another way as there is a risk of the plumbing being noisy otherwise. Remember never to use any jointing compound in connection with flexible plastic cisterns. The Water Regulations state that any new cisterns or replacement cisterns being installed are required to have an overflow pipe and a cover that excludes insects and light. They will also have to have thermal insulation to minimise the risk of damage from extreme temperatures.
Rigid Plastic Cisterns
These cisterns are made of polypropylene and are generally the same size as galvanised iron cisterns. This often makes them the first choice when a galvanised iron cistern has to be replaced. Unfortunately you cannot use jointing compound with these cisterns either and sometimes their sheer size makes it difficult to fit them through the loft hath. Luckily they come in different sizes and if you wanted to, you could install two smaller rigid plastic cisterns rather than a big one, as long as they are linked together. The connections should be installed to have a ball-valve connected to one of the cisterns and the cold water feeds to the other cistern. The reason for this is to avoid the water getting stagnant.