In the last few decades, polyethylene has been used as the most suitable material for manholes due to its favorable properties. The properties of the polyethylene manholes discussed below have led to an upward trend in their use, so that more than 80% of manholes currently used in recent projects in Europe are of these types.
Considering the proper properties of high density polyethylene (HDPE), the advantages of polyethylene manholes are as below:
1- Low weight
Due to the low density of polyethylene compared to concrete, the weight of the polyethylene manhole is much lower compared to concrete manholes with the same usage. Another advantage of the low weight is that in swampy and sandy grounds where the sub construction of ground for heavy manholes is impossible and also where the collapse of ground due to its looseness is more probable, these manholes are completely safe from the risk of collapse.
2- High strength against impact
Due to the inherent flexibility and impactibility feature of polyethylene, the manholes made from it have high resistance against impacts during transportation or installation.
3- Long lifetime
Due to the use of polyethylene, these kinds of manholes have very long life span.
4- High resistance to external loads due to proper bedding
5- high storage life, with coverage against direct sunlight, and the possibility of air circulation in Depo
6. Integrated and comprehensive system
Due to the fact that the polyethylene manhole is made in a comprehensive manner (implementation of all connections, stair, floor, cap, etc. at the factory site) and shipped to the installation site, it has a great advantage in saving costs and increasing the speed of the project implementation.
7- High chemical resistance in corrosive environments
Because of its intrinsic properties, polyethylene has excellent resistance against various chemicals. For this reason, the risk of corrosion and decay in the vicinity of corrosive substances and chemicals and acidic environments is very low.
8. High resistance against earth movements
Polyethylene manholes due to their flexibility (with their jointed polyethylene pipes) have a very high resistance against earthquakes and landslides.
9- Low piping costs
Manholes are also part of the piping system, and this cost in polyethylene is much lower than concrete one. Because the costs of bedding, preparing trenches, tools needed at workshop, etc., are lower in the polyethylene system.
10- low roughness
Due to the low coefficient of roughness of polyethylene pipes, the possibility of sticking suspended material and mud to it is very low, and if the mud lay on it, it will be completely washed and cleaned with the first flow of water. Due to the low roughness of polyethylene and the smooth surface of the manholes made from it, as well as the high abrasion resistance of polyethylene, its abrasion is ignorable against water, and this results in a long life span of these manholes, especially in the pipelines having a high tilt angle.
11-High installation speed
One of the biggest advantages of polyethylene manholes is their high installation speed. Due to the fact that polyethylene manholes are manufactured in prefabricated form, they are immediately installed after being shipped.
Types of manholes
1. Direct-Passage Polyethylene Manhole
2. Side-Passage Polyethylene Manhole