Radiator Working Pressure vs Test Pressure: What 15 and 25 atm Actually Mean
Radiator datasheets and catalogues state pressure in different ways: one manufacturer writes "working 15 atm, test 25 atm", another "1.0 MPa", a third "10 bar". For buyers and system designers this is one of the key selection parameters, so let us unpack what each figure means and how to compare products.
What working pressure is
Working pressure is the water pressure at which the radiator is designed to operate continuously throughout its service life. It must exceed the maximum pressure of your heating system, including surges. Typical reference points: an autonomous system in a single-family house — usually 1.5–3 atm; low-rise buildings with a substation — 4–6 atm; district heating in a high-rise — 6–10 atm, with short-term peaks during pressure testing and water hammer noticeably higher.
What test pressure is
Test pressure is the pressure at which strength and tightness are verified. Two different tests should be distinguished. The first is the factory test: the manufacturer checks the product with a standardised margin above working pressure. The second is the commissioning pressure test of the system itself, after installation or repairs: utilities typically test the network at 1.25–1.5 times working pressure. A radiator must withstand the system pressure test, not just everyday operation.
Where "15 and 25 atm" come from
The "15/25 atm" pair is the typical labelling of steel tubular radiators on CIS markets: 15 atm is the maximum working pressure, 25 atm the factory test pressure. Big numbers do not automatically mean a "better" radiator: they mean it is designed for high-rise district heating, where pressure on the lower floors is high and water hammer is likely. For a cottage with a closed 2 atm system such a margin is unnecessary — there, heat output, dimensions and coating quality decide.
MPa, bar, atm: how to convert
Manufacturers use three units, and mixing them up is a common source of specification errors. The rule is simple: 1 MPa = 10 bar ≈ 10.2 atm; in practice bar and atmosphere are treated as equal, the difference is under 2%. So "1.0 MPa", "10 bar" and "10 atm" are the same pressure. Russian GOST documentation uses MPa while trade catalogues use atmospheres, which is why JIUDING product pages for the Russian market show pressure in both units, MPa and atm.
Choosing a radiator by pressure
The algorithm is short. 1. Find out your system's working pressure from the building manager or designer. 2. Ask for the network's pressure-test value. 3. The radiator's working pressure must be no lower than the system test pressure. For a private house, 6–10 atm leaves a generous margin; for high-rise district heating look at radiators rated from 10 atm working pressure with a documented factory test; for especially demanding projects there are reinforced series, for example copper-aluminium radiators rated 1.6 MPa (16 atm).
Common misconceptions
First: "test pressure is usable operating headroom". No: a radiator must not be operated above its working pressure; it withstands test pressure briefly and without permanent deformation, but that is a verification mode, not an operating one. Second: "higher pressure figures mean longer service life". There is no direct link — steel quality, weld quality and water chemistry matter far more for longevity. Third: "pressure does not matter in a private house". It does: pressure is briefly raised when filling and testing the system, and water hammer from a quickly closed valve can occur in a cottage too.
How JIUDING tests
At the JIUDING factory every single unit — not a sample — undergoes a hydraulic test at 1.5 times working pressure: for series rated 1.0 MPa (10 atm) that means 1.5 MPa (≈15 atm). The test is part of multi-stage ISO 9001 quality control, and thermal performance is verified to the European EN 442 standard. Test reports and certificates are available in our documentation centre, with a summary on the Credentials page.
If you are specifying radiators for a particular project — a high-rise, hotel or housing development — send us the system parameters: working pressure, temperature regime and connection type. We will match a series with the right pressure margin from over 600 specifications.