Hydrocarbon separator

Q: What is a hydrocarbon separator and what is it for?

It is a unit that retains and separates light liquids (oils, diesel, petrol and petroleum derivatives) from water before discharge. It is used at petrol stations, workshops, vehicle wash bays, car parks, industrial units and roads. As well as being a legal requirement in many installations, it protects the environment by preventing contaminated water from reaching watercourses, the ground or the sewer network.

Q: How are hydrocarbons separated from water?

By difference in density: the hydrocarbons, being lighter, rise and are retained at the surface while the clean water leaves below. First the sand settles in the silt trap and then the oils and greases are separated; in class I units a coalescing filter merges the microdroplets to reach a discharge below 5 mg/L. An automatic closure device shuts the outlet when the hydrocarbon layer reaches its maximum.

Q: When is a hydrocarbon separator compulsory?

Whenever there is a risk that the water (rainwater or process water) may carry hydrocarbons: service stations, workshops, wash bays, car parks and paved surfaces where vehicles circulate or park, and industrial or logistics areas. The obligation and the specific conditions are set by the discharge authorisation of the river basin authority and by municipal and regional regulations.

Q: What is the difference between class I and class II (EN 858)?

Class I incorporates a coalescing filter and guarantees a discharge with less than 5 mg/L of hydrocarbons; it is required to discharge into a public watercourse or when maximum quality is demanded. Class II (without coalescing filter) allows up to 100 mg/L and is used when the effluent goes to a downstream treatment plant or the regulations allow it. When in doubt, class I is the safest option.

Q: Do I need a separator with or without a bypass?

The bypass is designed for large surfaces exposed to rain (car parks, roads): it treats the normal flow of lightly contaminated water and diverts the peak flow of storms, avoiding oversizing the unit. For process installations or small surfaces the model without bypass is usually enough. We help you decide according to your case.

Q: What size or flow rate of separator do I need?

The nominal size (NS) is calculated from the surface to be drained, the rainfall intensity of the area and the type of liquid, according to EN 858-2. The larger the impermeable surface and the greater the risk, the higher the NS. Tell us the surface, the use and the discharge point and we will size the exact unit.

Q: Is a silt trap necessary?

Yes, unless there is already an upstream sand chamber. The silt trap retains sand, soil and solids that would otherwise clog the coalescing filter and reduce performance. Many of our models incorporate it as an integrated unit; in others it is installed as a separate upstream chamber.

Q: How often does the separator need maintenance and emptying?

It must be inspected periodically and emptied when the hydrocarbon layer or the volume of sludge reaches its limit (usually once or twice a year, depending on use), always by an authorised waste manager. Correct maintenance — cleaning the coalescing filter and checking the closure device — guarantees performance and legal compliance.

Q: Which material should I choose: polyethylene, polyester or steel?

Polyethylene (PE) is light and highly resistant to corrosion, ideal for small and medium flow rates. Glass-fibre reinforced polyester (GRP) allows large capacities and burial at greater depth. Coated steel is used in compact and above-ground models. They all comply with EN 858; we advise you according to the flow rate, the location and the budget.

Q: How is a hydrocarbon separator installed?

Buried models are placed on a levelled sand bed (concrete slab and strap anchoring if the water table is high), backfilled with sand while being filled with water in layers, and connected with the correct slope and a vent pipe; the inspection cover must remain accessible. Modular models are integrated into a concrete structure and above-ground models on a levelled base. Always follow the unit’s manual and the local regulations.

Home » Water Treatment » Hydrocarbon separator

A hydrocarbon separator (oil separator) is a treatment unit that retains and separates light liquids from water (mineral oils, diesel, petrol and other petroleum derivatives) before discharge into the sewer network, a watercourse or the ground. It is essential wherever hydrocarbons are handled or may be spilled: petrol stations, workshops, vehicle wash bays, car parks, industrial units, logistics areas and roads.

At Inza we manufacture them in polyethylene (PE), glass-fibre reinforced polyester (GRP) and steel, in the class I versions (with coalescing filter, discharge < 5 mg/L) and class II, with or without integrated bypass and with a silt trap, in accordance with the EN 858 standard. A wide range of flow rates covers everything from a single wash bay to large paved areas.

Supply: delivery time to be confirmed, depending on the size and component stock.

Transport included in the price, excluding the unloading means at destination; for capacities over 5,000 L, please ask.

Questions or enquiries?

Phone: +34 91 127 90 05
WhatsApp: +34 91 127 90 05
Email: info@inzainox.com

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Compact coated steel hydrocarbon separators
Price range: €1.980,00 through €7.700,00 taxes not included Select options This product has multiple variants. The options may be chosen on the product page
Polyester hydrocarbon separators
Price range: €1.900,00 through €10.300,00 taxes not included Select options This product has multiple variants. The options may be chosen on the product page
Polyester hydrocarbon separators with bypass
Price range: €4.200,00 through €10.700,00 taxes not included Select options This product has multiple variants. The options may be chosen on the product page
Polyethylene hydrocarbon separators
Price range: €1.650,00 through €4.500,00 taxes not included Select options This product has multiple variants. The options may be chosen on the product page
Polyethylene hydrocarbon separators with bypass
Price range: €2.500,00 through €7.500,00 taxes not included Select options This product has multiple variants. The options may be chosen on the product page
Steel hydrocarbon separators with integrated bypass
Price range: €7.200,00 through €9.700,00 taxes not included Select options This product has multiple variants. The options may be chosen on the product page

How does a hydrocarbon separator work?

The hydrocarbon separator works by difference in density: hydrocarbons, being lighter than water, rise and are retained at the surface while the clean water leaves through the lower part. The process takes place in several stages:

Inlet and buffering: the contaminated water enters and slows down to favour separation.
Silt trapping: sand and coarse solids settle at the bottom (in models with an integrated silt trap or via an upstream chamber).
Separation by flotation and coalescence: the hydrocarbon droplets rise; in class I units, a coalescing filter merges the microdroplets to achieve a discharge below 5 mg/L.
Automatic closure device: a float closes the outlet when the hydrocarbon layer reaches its maximum volume, preventing it from escaping into the effluent.
Treated water outlet towards the sewer network, infiltration or the authorised discharge point.

Advantages of the Inza hydrocarbon separator

Choosing an Inza hydrocarbon separator means a high-quality, efficient and safe technical solution:

Regulatory compliance: units in accordance with EN 858, class I and class II, with guaranteed performance (< 5 mg/L in class I).
Wide range of materials: polyethylene (PE) by rotational moulding, glass-fibre reinforced polyester (GRP) and coated steel, for every type of installation (buried, above ground or modular in a concrete structure).
With or without bypass: the integrated bypass treats the normal flow of lightly contaminated water and diverts the peak flow of heavy rainfall, optimising the sizing.
Silt trap and coalescing filter integrated depending on the model, for maximum efficiency and less maintenance.
Automatic closure device that prevents accidental hydrocarbon discharge.
Durability and corrosion resistance, with a long service life.
Technical advice for sizing and choosing the unit, and stock for tight delivery times.

Why choose Inza hydrocarbon separators?

At Inza we have years of experience in drainage and water treatment systems. We manufacture hydrocarbon separators in polyethylene, polyester (GRP) and steel, in class I and class II, with or without bypass, in accordance with the EN 858 standard, and we support you throughout the whole process: sizing, choice of material, installation and maintenance.

Important notice: the information on this page is indicative and does not replace technical advice or the applicable regulations. Before installing a hydrocarbon separator you must consult your town council, the regional authority and the relevant river basin authority, since the type of unit required, the sizing, the minimum distances and the discharge authorisation vary according to the location and each specific case. Obtaining the permits and authorisations is the responsibility of the owner of the installation.

Further queries regarding our hydrocarbon separators

What is a hydrocarbon separator and what is it for?

It is a unit that retains and separates light liquids (oils, diesel, petrol and petroleum derivatives) from water before discharge. It is used at petrol stations, workshops, vehicle wash bays, car parks, industrial units and roads. As well as being a legal requirement in many installations, it protects the environment by preventing contaminated water from reaching watercourses, the ground or the sewer network.

How are hydrocarbons separated from water?

By difference in density: the hydrocarbons, being lighter, rise and are retained at the surface while the clean water leaves below. First the sand settles in the silt trap and then the oils and greases are separated; in class I units a coalescing filter merges the microdroplets to reach a discharge below 5 mg/L. An automatic closure device shuts the outlet when the hydrocarbon layer reaches its maximum.

When is a hydrocarbon separator compulsory?

Whenever there is a risk that the water (rainwater or process water) may carry hydrocarbons: service stations, workshops, wash bays, car parks and paved surfaces where vehicles circulate or park, and industrial or logistics areas. The obligation and the specific conditions are set by the discharge authorisation of the river basin authority and by municipal and regional regulations.

What is the difference between class I and class II (EN 858)?

Class I incorporates a coalescing filter and guarantees a discharge with less than 5 mg/L of hydrocarbons; it is required to discharge into a public watercourse or when maximum quality is demanded. Class II (without coalescing filter) allows up to 100 mg/L and is used when the effluent goes to a downstream treatment plant or the regulations allow it. When in doubt, class I is the safest option.

Do I need a separator with or without a bypass?

The bypass is designed for large surfaces exposed to rain (car parks, roads): it treats the normal flow of lightly contaminated water and diverts the peak flow of storms, avoiding oversizing the unit. For process installations or small surfaces the model without bypass is usually enough. We help you decide according to your case.

What size or flow rate of separator do I need?

The nominal size (NS) is calculated from the surface to be drained, the rainfall intensity of the area and the type of liquid, according to EN 858-2. The larger the impermeable surface and the greater the risk, the higher the NS. Tell us the surface, the use and the discharge point and we will size the exact unit.

Is a silt trap necessary?

Yes, unless there is already an upstream sand chamber. The silt trap retains sand, soil and solids that would otherwise clog the coalescing filter and reduce performance. Many of our models incorporate it as an integrated unit; in others it is installed as a separate upstream chamber.

How often does the separator need maintenance and emptying?

It must be inspected periodically and emptied when the hydrocarbon layer or the volume of sludge reaches its limit (usually once or twice a year, depending on use), always by an authorised waste manager. Correct maintenance — cleaning the coalescing filter and checking the closure device — guarantees performance and legal compliance.

Which material should I choose: polyethylene, polyester or steel?

Polyethylene (PE) is light and highly resistant to corrosion, ideal for small and medium flow rates. Glass-fibre reinforced polyester (GRP) allows large capacities and burial at greater depth. Coated steel is used in compact and above-ground models. They all comply with EN 858; we advise you according to the flow rate, the location and the budget.

How is a hydrocarbon separator installed?

Buried models are placed on a levelled sand bed (concrete slab and strap anchoring if the water table is high), backfilled with sand while being filled with water in layers, and connected with the correct slope and a vent pipe; the inspection cover must remain accessible. Modular models are integrated into a concrete structure and above-ground models on a levelled base. Always follow the unit’s manual and the local regulations.