Anyone installing drinking water, heating or gas lines today usually presses the joints instead of soldering or welding them. But not all press fittings are the same: stainless steel, carbon steel and copper differ considerably in their field of application, pressure rating, sealing ring and cost. A comparison of press fitting systems helps you choose the right system for every pipe and avoid typical mistakes, such as a galvanised steel heating system that accidentally ends up in the drinking water line.
In this guide we compare the three most important metal press fitting systems using the Sanha range as an example, briefly classify multilayer composite pipes and explain what matters with sealing rings, press contours and tools. The technical values are taken from the manufacturer's data. Whether pressing or soldering is the better choice in principle is answered in our guide Press Fittings vs. Solder Fittings, and the article Stainless Steel vs. Copper looks more closely at the choice of material for drinking water.
Design, sealing rings and press jaws
A press fitting system always consists of three components that are matched to each other: the fitting with an inserted sealing ring, the matching system pipe and the press tool with the correct contour. During pressing, the press jaw cold-forms the fitting and the pipe. The deformation holds the pipe mechanically in place, and the sealing ring seals the joint. If pipes, fittings or press jaws from different systems are combined, the joint is no longer covered by the manufacturer's testing.
The sealing ring determines the medium, and its colour makes it recognisable on site. According to the manufacturer, the following applies to Sanha: a black EPDM ring for drinking water and heating, a red FKM ring for solar and high-temperature applications and a yellow HNBR ring for gas installations. For the Sanha systems up to 54 millimetres, the manufacturer specifies press jaws with the original SA, V or M contours. Before using an existing tool, always check the approval in the installation instructions, because an incorrect contour can result in joints that initially appear tight during the pressure test but do not have the necessary holding force in operation.
The same procedure applies to every system: cut the pipe square, deburr it inside and outside, mark the insertion depth, push the fitting on up to the mark and press. A pipe that has not been deburred can damage the sealing ring when inserted, and a missing mark is the most common cause of pipes that have not been inserted far enough.
Stainless steel press fittings: drinking water and more
Stainless steel is the most versatile of the three materials. According to the manufacturer, Sanha's NiroSan system is made of chromium-nickel-molybdenum steel with material number 1.4404 and is intended for drinking water. According to Sanha, the joint is tested to DVGW W 534. The nominal pressure rating depends on the diameter: PN 40 for 15 to 22 millimetres, PN 25 for 28 to 35 millimetres and PN 16 from 42 millimetres. With an EPDM sealing ring, the permissible continuous temperature is minus 30 to plus 120 °C, briefly up to 150 °C.
In addition to the drinking water system, there are stainless steel variants for other tasks. According to Sanha, NiroSan SF is free of silicone and other substances that impair paint wetting, which matters in painting areas, for example, and the red FKM ring allows higher temperatures. NiroSan Gas works with a yellow HNBR ring and is tested to DVGW G 5614. NiroTherm, made of material 1.4301, on the other hand, is not approved for drinking water according to the manufacturer, but is intended for closed heating and cooling circuits, compressed air, technical gases and treated water. If you order a stainless steel pipe for drinking water, pay close attention to the system designation.
Carbon steel press fittings: closed circuits only
Carbon steel stands for unalloyed steel. According to the manufacturer, the Sanha system SANHA-Therm is made of steel with material number 1.0034 and galvanised on the outside. Sanha intends it only for closed circuits and expressly points out that it is not suitable for drinking water. The nominal pressure is PN 16, and the continuous temperature with an EPDM ring is minus 30 to plus 120 °C.
Typical applications are heating distribution, cooling circuits and systems with larger diameters where the price of the material plays a major role. The prerequisite is a closed circuit without a constant oxygen supply, because unalloyed steel corrodes on the inside if fresh, oxygen-rich water keeps flowing in. Carbon steel also needs protection against permanent moisture from the outside; details are given in the installation instructions. For thick-walled steel pipes, Sanha offers a separate system, Heavy Steel Press, which according to the manufacturer is processed with press jaws with the MP contour and is likewise not approved for drinking water.
Copper press fittings: the proven all-rounder
Copper press fittings have been widely used in drinking water and heating installations for many years. According to the manufacturer, SANHA-Press is made of Cu-DHP copper, fits copper pipes to EN 1057, is tested to DVGW W 534 and is designed for PN 16. For solar systems there is SANHA-Press Solar with an FKM ring, according to Sanha for continuous temperatures up to 160 °C depending on the medium and briefly up to 280 °C. SANHA-Press Gas with an HNBR ring is intended for gas installations.
Whether copper is suitable for drinking water depends on the water composition. With very soft or acidic water, copper can dissolve, so it is worth looking at the water supplier's analysis before planning. For transitions between copper and stainless steel pipes there are fittings made of lead-free silicon bronze, at Sanha the PURAPRESS range. Short pipe runs and regular water exchange are also important for hygiene, as described in the guide Drinking Water Hygiene.
The systems in direct comparison
The following table summarises the manufacturer's data for the three basic systems. It does not replace the installation instructions, but shows at a glance where the differences lie:
| Feature | Stainless steel (NiroSan) | Carbon steel (SANHA-Therm) | Copper (SANHA-Press) |
|---|---|---|---|
| Material | 1.4404 | 1.0034, galvanised outside | Cu-DHP |
| Drinking water | yes | no | yes, depending on water composition |
| Heating, closed circuits | yes | yes | yes |
| Nominal pressure | PN 40 to PN 16 depending on diameter | PN 16 | PN 16 |
| Continuous temperature with EPDM | minus 30 to plus 120 °C | minus 30 to plus 120 °C | minus 30 to plus 120 °C |
| Dimensions according to manufacturer | 15 to 168.3 mm | 12 to 108 mm | 12 to 108 mm |
| Variants | SF (silicone-free), Gas, NiroTherm for heating | Industry, Heavy Steel Press | Solar, Gas, PURAPRESS transitions |
In practice, this results in a simple allocation. For cold and hot drinking water and for circulation lines, stainless steel or copper are possible; the decision depends on the water analysis, the building and the budget. For heating distribution and cooling water in closed circuits, carbon steel is often the more economical choice, and stainless steel is also possible there. Solar circuits with high stagnation temperatures need a system with an FKM sealing ring, and gas needs a system with a yellow HNBR ring and gas approval. If several systems are used in one building, the pipes should be clearly labelled and the systems stored separately on site so that no fittings are mixed up.
In addition to the metal systems, there are multilayer composite pipes. According to the manufacturer, the Sanha MultiFit Flex system consists of an inner and outer pipe made of PE-RT with a butt-welded aluminium pipe in between and can be used in heating and drinking water installations. Such pipes can be bent and are light, but are processed with their own fittings and their own contour. You will find an overview of pipes and fittings for heating in the Heating Pipes and Press Fittings category.
Frequently asked questions
May I use carbon steel press fittings for drinking water?
No. According to the manufacturer, systems made of unalloyed, galvanised steel such as SANHA-Therm are intended only for closed circuits. For drinking water, stainless steel, copper or approved multilayer composite systems can be considered.
Can I combine fittings and pipes from different manufacturers?
The system testing applies to the combination of fitting, pipe and press jaw specified by the manufacturer. Mixing systems means leaving this testing. Therefore use the recommended system pipes.
How can I tell which medium a fitting is intended for?
By the system designation and the colour of the sealing ring. At Sanha, black stands for EPDM, red for FKM and yellow for HNBR for gas. If in doubt, the marking on the fitting and pipe helps.
Do I need a different press tool for stainless steel than for copper?
The pressing machine can often be the same; what matters are the press jaws with the approved contour. For the Sanha systems up to 54 millimetres, the manufacturer specifies the SA, V or M contours.
Conclusion
Stainless steel is the most versatile press fitting system and is suitable for drinking water, heating and, with its own variants, also for gas and special applications. Carbon steel is an economical solution for closed heating and cooling circuits but never belongs in a drinking water line. Copper remains a proven all-rounder, provided the water composition is suitable. In every case, the right system, the matching sealing ring and the approved contour are decisive. On request, our installation partners take care of installation at the customer's premises. You will find Sanha fittings and system pipes in our Sanha category.
