Blue PE Pipe and Fittings
Simply put, none! The world of polyethylene (abbreviated to "PE") pipe is a very confused one with different names being used over the last 50 years or so. This has lead to different people referring to it by different names but in short, if you are replacing a water supply pipe or putting in a new one to a house, round a farm, a golf course or to outbuildings this is the stuff you need.
An MDPE (or alkathene etc.) pipe system made up using blue water pipe uses several different materials. The pipe itself is made of polyethylene and the blue colour denotes it has been passed suitable for drinking (potable) water purposes. Polyethylene cannot be glued and so the only fittings that can be used with it are mechanical ones such as compression fittings, the most common of which are made of polypropylene wih EDPM O'rings. There are also some more specialist brass, stainless steel or other metal fittings, but these tend to be used very rarely. The pipe can also be joined using heat, but specialist machinery and training is required for this, which is usually out of the realm of most users.
If you are not sure what diameter of pipe you need for your application, you can check using our free online calculator which will calculate the headloss and flow rate for you.
If connecting to mains water, this usually runs at a pressure of between 2 and 4 bar but can be as low as 0.7 bar (the minimum required by OfWat) and can sometimes be higher. The source water pressure will have a great bearing on the amount of water you will get out of a pipe at the end of the run and so is often best checked first using a pressure gauge. Remember though, in some areas, the pressures can change throughout the day or at different times of year.
MDPE pipe has many benefits over using other materials for long supply runs. The nature of the plastic, being supplied in long coils rather than lengths, reduces the number of joints required (which are usually where a pipe system is compromised) and it's ductility makes it easy to bury as it won't be as affected by stones or other debris around it as other materials such as PVC. In fact MDPE pipe is so ductile it can actually be squeezed shut without damaging it. As the material is softer than other plastics, it can also withstand freezing better than more rigid plastics like PVC, ABS or Polypropylene (PP).
All our blue water pipe is WRAS approved for drinking water supplies in the UK (similar black pipe is often manufactured using a percentage of recycled material and so is not). OUr compression fittings are also WRAS approved, but only if used with liners. These must be used on each join and prevent the compression fitting from crushing the pipe which could theoretically cause leaks and possible contamination of the water supply. In truth a lot of non WRAS approved systems are installed without these liners, but the MUST be included to fully comply with WRAS approval.
If connecting any piece of equipment to an approved MDPE / Alkathene drinking water supply you must ensure that there is no possibility of contaminated water being drawn back into the pipeline. This can occur if for example the main has to be drained or flushed for maintenance work. WRAS regulations require either the installation of double check valves or an air break using something like a ballcock device. The fines for contaminating a mains water supply are VERY high and so best avoided!