ᐅ The underfloor heating circuit and the radiator heating circuit each have a maximum flow rate of 0.3 m³/h.
Created on: 16 Nov 2025 20:10
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WFJH2022Hello dear house building forum,
No matter how many circuits I open on the underfloor heating, I don’t get a flow rate higher than 0.3 m³/h (0.13 US gallons per second). For the second heating circuit, with all radiators set to 5, I manage about 0.4 m³/h (0.18 US gallons per second). Both pumps are running at full load. They should actually deliver 3.3 m³/h (1.45 US gallons per second) each at a head of 6.2 m (20.3 ft).
What I have done:
Cleaned the pump, but it wasn’t really dirty. Only a thin slimy layer.
Checked the dirt separator, but hardly any dirty water came out.
Flushed the underfloor heating with tap water as well, only some greenish to dark water, but no visible dirt.
Bypassing the underfloor heating circuits also did not increase the flow rate.
My installer says no additional filters are installed.
After the last feedback, the only remaining component is the hydraulic separator. However, here I have reached the end of my knowledge. When replacing and cleaning the pumps, the hydraulic separator was also drained. The first time, blacker water came out, but not typical sludge. The second time, during disassembly, it was relatively clear.
How can I clean this better, or is it possible to adjust the hydraulic separator? I hope for a solution or tip.
Many thanks for your help
Best regards
No matter how many circuits I open on the underfloor heating, I don’t get a flow rate higher than 0.3 m³/h (0.13 US gallons per second). For the second heating circuit, with all radiators set to 5, I manage about 0.4 m³/h (0.18 US gallons per second). Both pumps are running at full load. They should actually deliver 3.3 m³/h (1.45 US gallons per second) each at a head of 6.2 m (20.3 ft).
What I have done:
Cleaned the pump, but it wasn’t really dirty. Only a thin slimy layer.
Checked the dirt separator, but hardly any dirty water came out.
Flushed the underfloor heating with tap water as well, only some greenish to dark water, but no visible dirt.
Bypassing the underfloor heating circuits also did not increase the flow rate.
My installer says no additional filters are installed.
After the last feedback, the only remaining component is the hydraulic separator. However, here I have reached the end of my knowledge. When replacing and cleaning the pumps, the hydraulic separator was also drained. The first time, blacker water came out, but not typical sludge. The second time, during disassembly, it was relatively clear.
How can I clean this better, or is it possible to adjust the hydraulic separator? I hope for a solution or tip.
Many thanks for your help
Best regards
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