Why It’s Important to Understand the Types of Sewer Systems

Sewerage is not just a wastewater disposal system but a key element of the engineering infrastructure of any facility—from a private house to an industrial complex. It directly affects sanitary conditions, living comfort, and environmental safety. And if the water supply provides clean water, the sewerage system ensures that everything “excess” is removed quickly, safely, and without consequences.

The proper choice and arrangement of a sewerage system depend on numerous factors: the type of facility, site topography, groundwater level, the availability of centralized networks, and even the number of residents. Therefore, before building a house, renovating a cottage, or designing a warehouse, it is worth understanding what types of sewerage systems exist, how they are arranged, and what their fundamental differences are.

General classification of sewerage systems

All existing sewerage systems can be classified according to several criteria:

by the source of wastewater,

by the method of discharge,

by the location,

by the operating principle.

This classification helps better understand how engineering networks are arranged and which systems are suitable for specific conditions—whether it is an urban area, a private lot, or an industrial site.

Main types of sewerage by purpose:

Domestic sewerage – removes wastewater from bathrooms, kitchens, and toilets. This type of sewerage is installed in residential buildings, offices, and public institutions.

Storm sewerage – collects and discharges rainwater and meltwater from roofs, sidewalks, roads, and other surfaces.

Industrial sewerage – designed for collecting and treating wastewater containing technical or chemically active substances generated at production facilities.

By location, systems are divided into:

Internal sewerage. Includes all pipelines and sanitary fixtures inside a building: sinks, toilets, risers, traps, etc.

External sewerage. Covers pipelines, collectors, manholes, pumping stations, and treatment facilities located outside the building and responsible for transporting wastewater to the disposal or treatment point.

There is also a division by system organization:

Centralized sewerage (general connection to a city or village network).

Autonomous sewerage (an individual solution for one or several houses, common in private sectors, cottages, and remote areas).

In private and suburban houses, three sewerage types are most often combined: internal, external, and autonomous simultaneously.

When industrial sewerage is needed

Industrial sewerage is a specialized system designed for collecting, transporting, and treating wastewater generated at industrial facilities. Unlike domestic sewerage, this includes not only water from sanitary rooms but also complex wastewater that may contain oils, chemicals, abrasives, heavy metals, and other hazardous substances.

This system is required at:

plants and factories,

auto repair shops and car washes,

food and chemical enterprises,

warehouses and logistics facilities.

Features of industrial sewerage:

It uses pipes resistant to aggressive environments (for example, PVC, PE, or stainless steel).

Equipped with grease traps, sand traps, grates, and local treatment facilities (LTF).

Requires design considering the technological process, environmental protection standards, and production mode.

Such systems must be coordinated with the State Environmental Inspectorate. Without compliance with environmental safety norms, the enterprise will not receive permission for operation.

For example, at a car wash, wastewater containing car shampoo residues, oils, and dirt is produced daily. Industrial sewerage must include a sand trap, filtration system, and storage tank, from which water can be discharged into a centralized network—only after treatment.

Storm sewerage and drainage

Storm sewerage is a system designed for rapid removal of rainwater and meltwater from roofs, sidewalks, driveways, and surrounding areas. In Ukraine’s climate, where heavy rainfall and snowmelt are common, well-designed storm sewerage is essential for protecting the foundation, pavement, and the entire site drainage system.

Storm sewerage is most commonly installed:

in private houses and cottage settlements,

on the grounds of commercial and warehouse complexes,

near industrial facilities and parking lots.

Types of storm systems

Surface (open). The simplest form of storm sewerage—trays, gutters, and channels laid along walkways or foundations. They collect water and direct it to a sedimentation tank, drainage well, or canal.

Underground (closed). A system of pipes and storm inlets hidden underground. Ideal for areas with hard surfaces (asphalt, paving stones) and dense development.

Combined. Combines surface water collection with underground drainage. Often used on uneven sites or with height differences.

Elements of storm sewerage

Storm inlets (along blind areas and downspouts)

Trays and gutters

Sand traps

Serviceable inspection manholes

PVC, HDPE, concrete, or ceramic pipes

Common design mistakes

Incorrect pipe slope (water stagnates).

Absence of sand traps (blockages).

Insufficient capacity during heavy rainfall.

Discharging water onto neighboring plots or roads – violation of DBN V.2.5-75:2013.

In private construction, storm sewerage is often ignored. This leads to dampness in basements, foundation settlement, and premature pavement destruction. Even a simple drainage system with slope and trays can extend the lifespan of the entire structure.

Domestic sewerage

Domestic sewerage is a system designed for removing wastewater from bathrooms, kitchens, toilets, and other sanitary areas. It is the most common type of sewerage used in private houses, multi-apartment buildings, offices, schools, and other facilities.

Such wastewater includes:

water from washing, laundry, and dishwashing (“grey” water),

toilet waste from toilets and bidets (fecal, or “black” water).

It is the domestic system that ensures these liquids do not remain in the house, do not destroy floors, and do not create odors or unsanitary conditions. There are two main connection methods: centralized and autonomous sewerage.

Centralized sewerage system: reliable with caveats

Centralized sewerage is a system in which wastewater is discharged from the building through external networks toward municipal treatment facilities. This type is used in most apartment buildings, office centers, public institutions, and—more and more often—in new cottage settlements.

According to DBN V.2.5-64:2012, a centralized system includes:

internal building network of sewer pipes and risers;

external collectors;

pumping stations if necessary;

municipal collectors and central treatment facilities.

Where it is appropriate

In cities and towns with existing infrastructure.

In neighborhoods and townhouse developments planned for a unified connection.

At facilities where large wastewater volumes must be reliably removed (e.g., dormitories, schools, hospitals).

Advantages of centralized sewerage

High reliability when properly designed and operated.

No need for local treatment—everything goes to the municipal collector.

Minimal maintenance for the owner: cleaning and repairs are handled by the service provider.

Legal transparency—a contract with the water utility and meter-based billing.

Disadvantages and limitations

High connection cost: in Ukraine, the price depends on the distance to the manhole, terrain, and wastewater volume.

Mandatory technical specifications from the utility company (e.g., Kyivvodokanal).

Dependence on the city system: in case of overload or emergencies, backflows into the building are possible (especially on lower floors).

Not available everywhere: rural areas, outskirts, and cottage cooperatives often lack networks.

Centralized sewerage is convenient but not always feasible. For this reason, the demand for autonomous solutions in Ukraine continues to grow.

Choosing autonomous sewerage is always a balance between budget, site conditions, and the desired comfort level. And the higher the requirements for ecology, reliability, and hygiene—the more important it is to properly design the system and choose trustworthy equipment.

Autonomous sewerage for a private house

When connection to centralized sewerage is impossible or economically impractical, autonomous sewerage becomes the solution. This is a self-contained system that collects, transports, treats, and discharges wastewater independently. For private houses in Ukraine, this is the most common and flexible option.

An autonomous system can be adapted to any conditions: site size, number of residents, soil type, groundwater level, and even the frequency of residence.

Main types of autonomous sewerage

Pit latrine (cesspit, “old method”)

The simplest solution—a sealed or filtering tank into which all wastewater is discharged. Requires regular pumping.

Pros: low installation cost.

Cons: unpleasant odor, risk of soil contamination, non-compliance with modern sanitary standards.

Ideal for temporary living (dachas, garden houses).

Septic tank (multi-stage treatment)

A system of one, two, or three chambers where wastewater settles, partially decomposes, and filters. Often supplemented with infiltrators, filtration fields, or drainage wells.

Pros: easy maintenance, durability.

Cons: requires sufficient space, efficiency depends on soil quality.

Optimal for permanent residence of a family of 3–5 people under normal soil conditions.

3. LTF – local treatment facilities

High-tech biological treatment units (up to 95–98% purification). Wastewater is treated by bacteria, and the purified water can be used for irrigation. Requires electricity and minimal servicing.

Pros: high purification level, compactness, no odor.

Cons: high cost, dependent on electricity.

The best solution for modern suburban homes with urban-level comfort.

4. Biotoilets or mobile solutions

Suitable for temporary living, site cabins, construction sites. Do not require installation or connection but need regular replacement of cartridges and chemicals.

Choosing autonomous sewerage is always a balance between budget, site conditions, and desired comfort. And the higher the requirements for ecology, reliability, and hygiene—the more important it is to properly design the system and choose trusted equipment.

Structure, differences, and requirements for internal and external sewerage

Any sewerage system consists of two key components: internal and external sewerage. Their proper connection ensures smooth operation of the entire system—from the toilet in the house to the treatment facility beyond the site.

Internal sewerage (everything inside the house) includes:

sanitary fixtures (toilets, sinks, showers, bathtubs, kitchen sinks),

traps and floor drains,

horizontal pipelines,

risers,

inspection openings and ventilation outlets (vent stacks).

Main requirements:

Pipe slope—strictly according to DBN: from 2 to 3 cm per running meter (depending on diameter).

Avoid right angles: two 45° bends are better than one 90° turn.

Mandatory riser ventilation—prevents trap water from being siphoned out and eliminates odors.

Access to inspection points—for cleaning in case of blockage.

A common mistake: using cheap corrugated pipes or poorly secured pipes. This leads to sagging, leaks, and blockages within a few years of operation.

External sewerage (everything outside the house) is responsible for transporting wastewater from the building to the disposal point (central collector, septic tank, LTF, etc.).

It consists of:

pipelines (typically PVC, HDPE, or corrugated plastic),

inspection and revision manholes,

drainage elements (filtration wells, infiltration fields, drainage pipes),

pumping stations where needed (for areas with difficult relief),

connection nodes to the main collector or local treatment system.

Main requirements for external sewerage:

Correct pipe depth — below the frost line (for most Ukrainian regions this is 0.9–1.2 m).

A stable slope toward the collector — typically from 1–2 cm per meter, depending on diameter.

Use of solid, non-corrugated pipes for underground installation — to prevent deformation.

Mandatory installation of inspection manholes every 25 meters and at every direction change.

Protection from groundwater and soil shifts.

Correctly designed external sewerage prevents pipe freezing, backflows, blockages, and soil erosion. Most issues in private houses — unpleasant odors, gurgling, leaks — arise precisely due to mistakes in external system installation.

External sewerage by type of wastewater flow

When designing an external sewerage system, it is important not only to correctly choose the pipes and slope but also to determine how exactly different types of wastewater will be transported. There are three main schemes of wastewater flow organization: combined, separate, and semi-separate sewerage. Each of them has its own advantages and limitations — especially considering the Ukrainian climate, standards, and the condition of the infrastructure.

1. Combined sewerage system

This is a system in which all types of wastewater — domestic and stormwater — are discharged through the same pipes. This scheme is often used in older city districts where there is no separate stormwater network.

Advantages:

minimal construction costs (a single pipe network),

simplicity of initial design.

Disadvantages:

system overload during heavy rains or snowmelt;

high risk of wastewater backflow;

requirement for powerful treatment facilities;

environmental risks in case of leakage.

In new private and urban projects, combined systems are practically not used — they are outdated both morally and technically.

2. Separate sewerage system

In this scheme, domestic and stormwater flows are collected through separate pipelines and directed to different treatment or disposal facilities.

Advantages:

reliability and fault tolerance;

reduced load on each system;

possibility to reuse treated stormwater for irrigation or discharge into soil.

Disadvantages:

higher cost of design and installation (two parallel networks);

requires more space on the plot;

need for coordination of two systems (especially in winter).

For private houses with a plot of 600 m² or more — this is the best option.

3. Semi-separate sewerage system

An intermediate option in which stormwater and domestic wastewater are initially collected separately but merge into a single collector and are sent to common treatment.

Where it is used:

in areas with limited space;

on plots where it is impossible to organize a full-fledged stormwater system;

in projects where treatment is performed at a single station.

Advantages:

cost savings at the final part of the system;

more reliable than a combined system.

Disadvantages:

risk of collector overload during peak precipitation;

more complex maintenance.

What should a private developer choose?

Criterion	Combined	Separate	Semi-separate
Installation cost	Low	Medium–high	Medium
Environmental friendliness	No	Yes	Conditional
Reliability	Low	High	Medium
Recommended for	Old developments	Private houses, cottages	Dense development

If a house is being built from scratch, choose a separate sewerage system. It is more expensive at the start, but in the long run it prevents problems with odors, flooding, and issues with environmental inspection authorities.

How to choose a sewerage type — step-by-step guide

Choosing a sewerage system for a house or plot is not just a technical decision. It affects comfort, safety, durability of operation, and even future maintenance costs. To avoid mistakes, use this step-by-step guide based on practical design and installation experience in Ukraine.

Step 1. Assess the location and access to the centralized network

Are you within a settlement with access to a central sewerage system?

Is there a technical possibility to connect and under what conditions (contract, technical requirements, fees)?

How reliable is the existing network in your area (old pipes, failures, frequent blockages)?

If connection is possible and cost-effective — it is usually the best choice. The centralized system frees you from maintenance and treatment issues.

Step 2. Determine wastewater volumes

How many people will live in the house permanently?

Will there be washing machines or dishwashers?

Are a bathhouse, sauna, or jacuzzi planned — sources of increased wastewater?

For a family of 3–4 people, the daily wastewater volume is around 500–800 L/day. This is important for calculating the septic tank or biological treatment station capacity.

Step 3. Evaluate the plot area and terrain

Is there space for a septic tank, infiltrator, or filtration field?

What is the groundwater level?

Does seasonal flooding occur after rains or in spring?

A small plot with a high groundwater level may require a sealed tank and frequent pumping. With sufficient space, full treatment systems with soil discharge can be used.

Step 4. Choose the type of system: centralized or autonomous

Condition	Recommended option
Centralized network nearby	Connection to the network
No access to central sewerage	Autonomous system
High groundwater level, clay soil	Hermetic septic tank + pumping
Sandy soil, normal groundwater level	Septic tank + soil filtration
No electricity	Gravity system without a pump

Step 5. Define the budget and maintenance plan

If you want minimal upfront costs — choose a cesspit (but this is a temporary solution).

If you are ready to invest in environmental safety — install an aeration tank or a septic tank with bio-filtration.

If you do not have time for maintenance — sign a service contract with a company.

Choosing a sewerage system is a balance between budget, reliability, convenience, and sanitary requirements. Treat this decision not as a one-time task but as a long-term investment in comfort and ecology. A properly designed and installed system will work for decades without odors, flooding, or unnecessary expenses.

The right choice is the key to an efficient sewerage system

Sewerage is not just a technical part of the house but a key to hygiene, comfort, and environmental safety. If designed consciously, considering all factors — from terrain to wastewater volumes — typical mistakes can be avoided: bad smells, blockages, overflow, frequent pumping, or problems with sanitary authorities.

Designing a sewerage system requires precise assessment of conditions: from development density to seasonal groundwater fluctuations. There is no universal solution — each system has its own limitations, maintenance requirements, resources, and regulatory norms.

For urban development, the priority remains centralized systems that ensure scalability and control. For low-rise and suburban areas — autonomous systems with local treatment, adapted to the specific plot. In commercial and industrial projects, design loads, environmental protection standards, and resistance to extreme impacts become priorities.

The engineer’s key task is to provide a reliable, compliant, and economically justified infrastructure integrated into the overall water and engineering balance of the territory.

The designer must consider not only the calculated wastewater volumes but also non-standard load scenarios — seasonal occupancy, rainfall peaks, emergency discharges. This helps avoid system overload, especially on autonomous and combined solutions. Add reserve capacity and plan service points already at the project stage.