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Septic tanks

Septic tanks are a practical sewerage solution for private houses and properties without access to a central sewer. Our septic tanks are made of glass-fibre reinforced plastic (GRP) and are corrosion resistant.

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septic tank side view

How does a septic tank work?

01

Inflow

All wastewater from the house flows through a pipe into the first chamber of the septic tank, where the slow flow rate starts the mechanical treatment process.

02

Settling

Heavy particles sink to the bottom of the tank and form a sludge layer, while lighter matter stays at the top.

03

Decomposition

Anaerobic bacteria in the middle layer break down organic matter, and the water flows through small openings into the last chamber.

04

Infiltration

The mechanically treated water flows into an infiltration field or tunnels, where the natural filtration stage takes place.

How to choose a septic tank

1. Determine the number of residents
The first criterion is the number of people who will use the sewerage system every day.

2ā€“4 people: a 2 mĀ³ (2000 L) septic tank is suitable.
4ā€“6 people: a 3 mĀ³ (3000 L) septic tank is suitable.
6ā€“10 people: a 5 mĀ³ (5000 L) septic tank is suitable.

Calculations assume an average water consumption of 150ā€“200 litres per person per day.

2. Calculate water consumption
The septic tank volume should be at least 3 times the household’s daily water consumption. This keeps wastewater in the tank for at least 3 days, allowing heavy particles to settle fully.

3. Assess the soil
A septic tank’s performance depends directly on the infiltration field.

If your property has sandy soil, the system will work efficiently at the standard volume.
If the soil contains more clay or the groundwater is high, choose a larger volume to reduce the load on the infiltration system.

4. Plan the emptying frequency
A larger septic tank means less frequent emptying. Choosing a slightly larger tank (e.g. 3 mĀ³ instead of 2 mĀ³) gives you an extra “safety cushion” when you have guests or use more water than usual.

Volume Length Width Users Price (incl. VAT)
2mĀ³ 2000 mm 1200 mm 3-4 1650 ā‚¬
3mĀ³ 2900 mm 1200 mm 4-6 1850 ā‚¬
4mĀ³ 3750 mm 1200 mm 6-8 2500 ā‚¬
5mĀ³ 4650 mm 1600 mm 8-10 2890 ā‚¬
6mĀ³ 2800 mm 1600 mm 10-12
7mĀ³ 3300 mm 1600 mm 12-15
8mĀ³ 4300 mm 1600 mm 14-17
9mĀ³ 4750 mm 1600 mm 16-20
10mĀ³ 5300 mm 1600 mm 16-22
Completed project

AUGUST AT-20 for a future guesthouse in Ventspils municipality: when an old inn comes back to life.

History meets modern technology It’s not every day we get to take part in a project where new technology gives a second life to a historic building. An interesting project is under way in Ventspils municipality ā€“ an old inn…

Read more…
AUGUST AT-20 toposĢŒajam viesu namam Ventspils novadaĢ„ kad senais krogs atguĢ„st dziĢ„viĢ„bu

Frequently asked questions

What is a septic tank and how does it work?
A septic tank is a practical sewerage solution for private houses without access to a central sewer. It consists of a sealed tank with several chambers where two processes take place: mechanical settling (heavy particles sink) and anaerobic digestion (bacteria break down the organic layer). The clarified water then soaks into the ground through an infiltration field.
How does a septic tank differ from a biological treatment plant?
The main difference is the method and quality of treatment:nnSeptic tank: works without electricity, relies on natural settling and needs a large infiltration field, because the water leaving a septic tank is still heavily polluted.nnBiological plant: uses a compressor (aeration) and bacteria that treat the water to 98% quality, so it can be discharged into the environment.
What septic tank volume should I choose?
The choice depends directly on the number of people in the household: 2ā€“4 people: a 2 mĀ³ (2000 L) septic tank. 4ā€“6 people: a 3 mĀ³ (3000 L) septic tank. 6ā€“10 people: a 5 mĀ³ (5000 L) septic tank. The septic tank volume should be at least 3 times the daily water consumption so that water stays in the tank for at least 3 days.
Can a septic tank be installed in any soil?
No. A septic tank's performance depends directly on the infiltration field. The system works efficiently in sandy or gravel soil. If the property has clay or high groundwater, infiltration will be difficult, so a larger tank or a biological treatment plant is recommended.
How often does a septic tank need emptying?
A septic tank needs emptying less often than a holding tank ā€“ on average once every one or two years, to remove the sludge that collects at the bottom. Regular maintenance keeps the infiltration field working and prevents polluted wastewater from reaching the environment.