What's the difference between PE vs Alkathene vs Polyethylene vs MDPE
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.
Materials in an MDPE (Alkathene) Pipe System
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.
How to Size your Pipe System
If you are not sure what diameter of pipe you need for your application, you can
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.
Benefits of using MDPE / Alkathene for water supply projects
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).
Ensuring Your System is WRAS compliant
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.
Connecting your Potable Water Supply to Equipment
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!