The rainwater drainage system must be designed taking into consideration some valuable aspects to keep it efficient over time. Oils, hydrocarbons and chemical substances that are dispersed on the surface of petrol stations or forecourts and then carried away by rain can corrode drainage channel and accelerate their ageing.

Below you will find some of the major chemicals-related problems that can arise and the correct precautions to take in order to ensure maximum efficiency of the channels.

Rainwater collection with drainage channel

1. Rainwater collection channels of SAB.

Different kind of drainage channels used in petrol stations and forecourts

An interesting reference case concerning the application of drainage channels is related to petrol stations and forecourts. In this case, the channels are subjected to the corrosive action of the oily substances, fuels and soaps that are released and then transported by rainwater.

In addition, many petrol stations that are located outside the city centres are not connected to the sewerage system and therefore need their own system for collecting rainwater, toilet waste water and the treatment of detergents used for car washing.

The most commonly used types of channels in service stations are the followings:

  • Channels made of plastic materials (polyethylene or polypropylene)
  • Concrete channels
  • Channels made of concrete polymers

According to the Italian Legislative Decree no. 152 of 3 April 2006. The “Testo unico sulle acque” containing “Environmental regulations”, once contaminated rainwater is collected from the channels, it must be treated by a specific rainwater treatment plant.

drenaggio stazioni di servizio

2. Drainage system with SABdrain channels in petrol stations.

Chemical resistance of drainage channels

As already mentioned, chemical substances can often be a factor to consider when designing or purchasing drainage channels. Oils and solvents have the tendency to corrode and affect channel walls and accelerate their deterioration. The ability to resist against chemicals, also known as ‘chemical inertia’, depends on the type of material used. For example, the chemical resistance of concrete is not high and this is inversely related to its porosity and permeability.

Plastics, on the contrary, are much more resistant to chemicals, and are therefore preferred in cases where drainage systems need to be constructed in service stations or forecourts. Find below the table that compares the two materials (plastic and concrete) among others.

resistenza chimica dei canali di drenaggio

3. Table of chemical resistance of polypropylene drainage channels. A: No effect – Excellent; B: Irrelevant effect – Good; C: Moderate effect – Average; D: High effect – Not recommended.

Another substance that can affect the integrity of concrete is salt. Road maintenance agencies are very often forced to spread salt to prevent frost development, due to the extreme winter temperatures. Rainwater channels on roadsides or near petrol stations can carry dissolved salt, which then comes into contact with the walls and accelerates wear and tear.

Possible solutions

Among the possible precautions that can be taken there is the protection of the concrete through the use of coatings or protections to preserve the channel walls. Otherwise, a more practical and effective solution is to use polypropylene drainage channels, which provide excellent chemical resistance as well as quick installation.