I've been told I need a 25/6 rated circulating pump for the central heating. What doe these numbers mean exactly. I want to know because I discovered my existing pump is rated for a 6m head.


It has been a few years since I looked at specs on one but the two numbers are identified as Q/H or (m3/h by m). (m = meters)
To my understanding Q is volume of flow in m³/h (25), so how many cubic meters of liquid can flow in a hour period.
With H is delivery head in m (height) which is the height you can pump a liquid to straight up.
These are the basic description for standard values. In an exact case to determine what values are needed in a specific application would be based on all the variables such as pipe sizes in the entire system, desired pressures, suction tank/source levels and more.

  • thanks - have you any idea why so many are sold as 25/6 but there seems to be no other ratings ( that I can see visible in the ads). Oct 20 '16 at 20:43
  • I would only render a guess that common applications for most part are standardized or have regulation limits. On a quick look I see a few variations. Oct 20 '16 at 22:06

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.