Turning geothermal potential into sustainable heat
The region around Septemvri, located at the foot of the Rhodope Mountains, benefits from natural thermal springs situated approximately 13 kilometres from the town and four kilometres from the village of Varvara. The municipality sought to utilise this geothermal resource to provide clean, affordable heat to local communities. The objective was to increase living standards, reduce dependence on fossil fuels and stimulate wider economic development, particularly in tourism and wellness services.
The project faced severe constraints due to the mountainous topography. Steep gradients, narrow access routes and riverbanks restricted available construction space. A flexible and robust solution was essential to overcome these environmental challenges.
Why PB-1 piping was selected
The municipality identified Flexalen® 600 PB-1 pipes as the only system capable of meeting the technical and logistical requirements. Key advantages included:
- High flexibility and low weight enabled efficient transport across inaccessible terrain and permitted long continuous pipe runs with minimal joints
- Up to 100 times fewer connection points than traditional materials significantly reduced installation time and future maintenance exposure
- Chemical resistance ensured reliability when transporting geothermal water with high mineral and gas content
- Rapid installation with minimal environmental disturbance due to reduced trenching and limited machinery
These characteristics reflect the inherent material performance of PB-1, which provides a combination of flexibility, long-term creep resistance and robust service life under elevated temperature and pressure conditions.
Project execution
The municipality implemented the scheme using the Flexalen® 600 Cradle to Cradle Certified® pre-insulated PB-1 system throughout. Installation took place across three phases between spring 2017 and autumn 2024:
Phase 1
Installation of the main pipeline from the geothermal springs to the village of Varvara.
4,200 metres of 125/200 mm pipe.
Phase 2
Development of the Varvara village network supplying the kindergarten, school, library and cultural house together with future municipal building connections.
1,100 metres of 90/160 mm pipe and 420 metres of 75/160 mm pipe plus smaller diameters for service connections.
Phase 3
Construction of the main pipeline from Varvara to Septemvri and the associated city network.
10,000 metres of 125/200 mm pipe with an additional 3,000 metres for local distribution.
Phases 1 and 2 were completed by Megainvest Holding and phase 3 by Buildkom. Project management was led by MILOV and MEKOM.
“Some installation locations were very inaccessible, but Flexalen® 600 flexibility and lightweight enabled coils transportation without machinery for hundreds of metres, or even float them down small rivers. Any other material would have taken three years to install. With Flexalen®, we finished in months.”
Anton Tcholakov, installer and technical coordinator, MEKOM
Outcomes and benefits
The geothermal network now provides stable, ecological heating to public buildings and residences in both Septemvri and Varvara. Principal benefits include:
- Adoption of renewable heat
Geothermal energy now replaces conventional fossil fuels, improving air quality and system sustainability. - Significant reduction in CO₂ emissions
The switch from coal, oil and wood pellets reduces greenhouse gas emissions and local pollution. - Economic stimulus
The reliable heating infrastructure creates opportunities for thermal SPA development, attracting investment and supporting job creation. - Long-term operational security
The minimised number of joints reduces lifetime risk, while the mechanical performance of PB-1 supports decades of service.
Conclusion and more information
This project demonstrates how pre-insulated piping systems enable municipalities to realise the full potential of natural energy sources. The use of flexible pre-insulated PB-1 pipes allowed the installation of a complex district heating network in challenging terrain with lower environmental impact and higher long-term reliability.
For more information, visit the Thermaflex website.
Turning geothermal potential into sustainable heat
The region around Septemvri, located at the foot of the Rhodope Mountains, benefits from natural thermal springs situated approximately 13 kilometres from the town and four kilometres from the village of Varvara. The municipality sought to utilise this geothermal resource to provide clean, affordable heat to local communities. The objective was to increase living standards, reduce dependence on fossil fuels and stimulate wider economic development, particularly in tourism and wellness services.
The project faced severe constraints due to the mountainous topography. Steep gradients, narrow access routes and riverbanks restricted available construction space. A flexible and robust solution was essential to overcome these environmental challenges.
Why PB-1 piping was selected
The municipality identified Flexalen® 600 PB-1 pipes as the only system capable of meeting the technical and logistical requirements. Key advantages included:
- High flexibility and low weight enabled efficient transport across inaccessible terrain and permitted long continuous pipe runs with minimal joints
- Up to 100 times fewer connection points than traditional materials significantly reduced installation time and future maintenance exposure
- Chemical resistance ensured reliability when transporting geothermal water with high mineral and gas content
- Rapid installation with minimal environmental disturbance due to reduced trenching and limited machinery
These characteristics reflect the inherent material performance of PB-1, which provides a combination of flexibility, long-term creep resistance and robust service life under elevated temperature and pressure conditions.
Project execution
The municipality implemented the scheme using the Flexalen® 600 Cradle to Cradle Certified® pre-insulated PB-1 system throughout. Installation took place across three phases between spring 2017 and autumn 2024:
Phase 1
Installation of the main pipeline from the geothermal springs to the village of Varvara.
4,200 metres of 125/200 mm pipe.
Phase 2
Development of the Varvara village network supplying the kindergarten, school, library and cultural house together with future municipal building connections.
1,100 metres of 90/160 mm pipe and 420 metres of 75/160 mm pipe plus smaller diameters for service connections.
Phase 3
Construction of the main pipeline from Varvara to Septemvri and the associated city network.
10,000 metres of 125/200 mm pipe with an additional 3,000 metres for local distribution.
Phases 1 and 2 were completed by Megainvest Holding and phase 3 by Buildkom. Project management was led by MILOV and MEKOM.
“Some installation locations were very inaccessible, but Flexalen® 600 flexibility and lightweight enabled coils transportation without machinery for hundreds of metres, or even float them down small rivers. Any other material would have taken three years to install. With Flexalen®, we finished in months.”
Anton Tcholakov, installer and technical coordinator, MEKOM
Outcomes and benefits
The geothermal network now provides stable, ecological heating to public buildings and residences in both Septemvri and Varvara. Principal benefits include:
- Adoption of renewable heat
Geothermal energy now replaces conventional fossil fuels, improving air quality and system sustainability. - Significant reduction in CO₂ emissions
The switch from coal, oil and wood pellets reduces greenhouse gas emissions and local pollution. - Economic stimulus
The reliable heating infrastructure creates opportunities for thermal SPA development, attracting investment and supporting job creation. - Long-term operational security
The minimised number of joints reduces lifetime risk, while the mechanical performance of PB-1 supports decades of service.
Conclusion and more information
This project demonstrates how pre-insulated piping systems enable municipalities to realise the full potential of natural energy sources. The use of flexible pre-insulated PB-1 pipes allowed the installation of a complex district heating network in challenging terrain with lower environmental impact and higher long-term reliability.
For more information, visit the Thermaflex website.
