Materials · Profile
Copper materials: Cu-DHP, gunmetal, silicon bronze, brass
Four materials that sit side by side on the installation shelf and are all “made of copper” – and yet four different things: the tube, two fitting materials of the press systems and the brass of compression and push-fit connectors. This profile explains what the short names mean, where each one is found in our range, how to tell them apart by colour, magnet and certificate, and where the mix-ups lie.
- Family
- Copper and copper alloys – all non-magnetic, all reddish to yellow
- The four
- Cu-DHP (tube) · gunmetal (cast fitting) · silicon bronze (wrought fitting, lead-free) · brass CW617N (compression and push-fit connectors)
- In our range
- Copper tube EN 1057 from stock · gunmetal/silicon bronze in Sanpress and Profipress · brass at Gebo and Conex
- Identify
- Certificate and stamp first · colour · non-magnetic · cast vs. wrought surface
What the short name says
In the European system, copper materials carry two names: a short name made of element symbols and a material number following the pattern CW024A – C for copper, W for wrought, a serial number and a letter for the alloy group. Cast materials are called CC (cast). The short name is the reading aid:
| Material | Key elements | What characterises it | Typical use in our range |
|---|---|---|---|
| Cu-DHP (CW024A) | Pure copper, deoxidised with phosphorus, at least 99.90 % copper | The tube material of EN 1057: solderable, pressable, in three tempers R220 annealed, R250 half-hard, R290 hard. Not an alloy – the temper decides whether it comes in coils or straight lengths. | Copper tube EN 1057 – drinking water, heating, gas, solar |
| Gunmetal | Copper with tin, zinc and lead – a casting alloy (CC number) | For decades the fitting material of drinking water installations: easy to cast, corrosion-resistant, red-brown. Contains lead as a casting aid – which items the manufacturer makes in gunmetal and which in silicon bronze is stated in the current catalogue. | Press fittings Viega Sanpress and Profipress (existing items), threaded parts, adaptors |
| Silicon bronze (CuSi) | Copper with silicon – a wrought alloy, lead-free | The new fitting material of the press systems: hot-pressed instead of cast, without lead, with the resistance of gunmetal. “Bronze” here means silicon as the main addition, not tin. | Press fittings Viega Sanpress and Profipress (per item according to catalogue) |
| Brass CW617N | Copper with around 40 % zinc and some lead for machining | The material for turned and forged parts: yellow, easy to machine, economical. Not inherently dezincification-resistant – for that there are DZR brasses (such as CW602N, CW511L), which the manufacturer states per item. | Compression connectors Gebo multigebo/polygebo, push-fit fittings Conex >B< Push, valves, adaptors |
Key elements in prose based on the short names EN 1412/EN 1173; tempers and detailed composition are given in the certificate and the manufacturer documentation. Gunmetal and silicon bronze: material information according to the Viega catalogue 2026; brass: according to the Gebo and Conex catalogues.
Why four materials for one piping system
The tube has to bend and press – for that, pure copper in the right temper is unbeatable. The fitting has to be a complex part with a press bead and seal groove – that needs an alloy that can be cast (gunmetal) or hot-pressed (silicon bronze). The connector with thread, compression ring and union nut has to be machined economically – that is what brass is for. All four are electrochemically compatible, so a copper tube can run into a brass compression connector or a gunmetal press fitting without concern. The flow rule of mixed installations (base before noble) concerns the pairing with galvanised steel, not pairings within the copper family: Mixed installation and corrosion.
Lead has been the topic of recent years: gunmetal and free-machining brass contain it, silicon bronze and lead-free brasses do not. Whether an item is approved for drinking water is decided by the manufacturer’s approval of the system (DVGW, material list of the German Environment Agency) – not by the material name. We reproduce these approvals per system as the manufacturer issues them.
Source note: material per item and drinking water approvals as manufacturer information (Viega catalogue 2026, Viega media list); the classification of the material roles is our statement about our range.
Examples of where the material is found in our range
| Material | In our range | Page |
|---|---|---|
| Cu-DHP | Copper tube EN 1057 in coils (R220) and straight lengths (R250) from stock, with solder fittings and press fittings | Copper tubes |
| Gunmetal | Press fittings and adaptors Sanpress/Profipress – gunmetal or silicon bronze per article according to the manufacturer’s catalogue | Viega Sanpress · Viega Profipress |
| Silicon bronze | Press fittings Sanpress and Profipress, lead-free (manufacturer’s information) | Viega Profipress · Viega Sanpress |
| CW617N | Compression couplings for multilayer and plastic pipe, push-fit fittings, threaded adaptors | Joining without welding · Plastic compression couplings · multigebo |
Source note: stock levels according to our ERP survey (as of 10/2026: copper tube and Profipress in stock); gunmetal or silicon bronze per item according to the manufacturer’s catalogue, which is always the current reference since the assignment changes frequently.
Identifying the part – in this order
1. Paperwork first. Copper tube carries the continuous marking to EN 1057 (standard, size, temper, manufacturer, date) – how to read it is explained on the copper tube page. Fittings carry the manufacturer’s mark and system identifier; the material is stated in the catalogue.
2. Colour. Pure copper is salmon-red and tarnishes brown. Gunmetal is red-brown and matt, with the slightly grainy surface of a casting. Silicon bronze is reddish-golden and smooth (forged, not cast). Brass is yellow. Nickel- or chrome-plated parts give nothing away – only a fresh cut edge helps there.
3. Magnet. All copper materials are non-magnetic. If the magnet sticks, it is not a copper material – probably a copper- or brass-plated steel part.
4. Cast vs. wrought. Cast parts (gunmetal) show mould seams, gate remnants and a grainy skin; wrought parts (silicon bronze, brass) are smooth with turning or forging marks. This separates gunmetal from silicon bronze more reliably than colour.
Limit: identifying the material on the part indicates the probable family – not the alloy, batch or suitability for drinking water, and it does not replace a manufacturer’s certificate. Dezincification resistance and lead-free status cannot be seen on a brass part; they are stated only in the catalogue or the certificate.
What the certificate must show
Copper tube to EN 1057 usually comes with a declaration of compliance 2.1 or test report 2.2 to EN 10204; for drinking water tube this includes the manufacturer’s quality mark or DVGW registration, which the tube print carries. Press system fittings have no individual certificate – their proof is the system approval (DVGW registration number, manufacturer’s declaration on lead-free status or on the material list). Anyone who needs a 3.1 on copper tube for a project should say so when ordering – the mill then issues it; obtaining it afterwards is hardly possible: Inspection documents to EN 10204.
The typical mix-ups
“Gunmetal is brass.” No – gunmetal has tin as its main addition and is a casting alloy; brass has zinc and is mostly a wrought material. Red-brown vs. yellow, grainy vs. smooth.
“Bronze is gunmetal.” Almost – gunmetal is a tin bronze with zinc and lead, silicon bronze an entirely different alloy without tin and without lead. When a manufacturer writes “bronze”, it is worth asking which one.
“Brass is always dezincification-resistant.” No – CW617N is not. Dezincification-resistant brasses are separate materials that the manufacturer marks DZR or CR. For drinking water, the approval per item counts.
“Soft copper tube is inferior.” No – R220 is the same material in the annealed temper, intended for coils and hand bending. R250 is the straight length of installation work, R290 the hard tube for special cases. The wall is the same, the temper is not.
Further reading
The world of materials: Austenitic stainless steels · Ferritic stainless steels · Cast iron materials · Materials overview.
In the knowledge base: Copper tubes EN 1057 · Viega Profipress · Viega Sanpress · Joining without welding · Mixed installation and corrosion · Sealing elements and media.
Frequently asked questions
What is the difference between gunmetal and brass?
Gunmetal is a casting alloy with tin as the main addition - red-brown, with a grainy casting skin. Brass has zinc as the main addition, is yellow and mostly turned or forged.
May I mix gunmetal and silicon bronze fittings in one line?
Within the same press system, yes – the manufacturer offers both materials in the same system and approves them together (manufacturer information Viega). The press connection and the sealing element are the same.
Is brass permitted for drinking water?
Only in the alloys and items the manufacturer designates for it (dezincification-resistant, material list of the German Environment Agency, DVGW). CW617N as a free-machining brass is not intended for this. We reproduce the manufacturer’s approval per item.
How can I tell whether a copper tube is hard or soft?
From the print (R220, R250, R290) and the delivery form: coils are annealed, straight lengths half-hard. Only R220 can be bent by hand.
Do I need a 3.1 certificate for copper tube?
For domestic installations usually not – the marking and the manufacturer’s registration are sufficient. For plants with acceptance testing, yes; please say so when ordering.
Copper tube, press fitting or compression connector?
Tell us the medium, size and type of connection – we will tell you which copper material is in the right system and what is available from stock.
Send an inquiryYour inquiry to Zickwolff
Send us what you have – designation, standard, quantity, date. We will clarify the rest with you.
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Designation, standard and quantity are enough.
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As of 2026-10-24. Material statements as manufacturer information (Viega catalogue 2026 and media list, Gebo and Conex catalogues) and from the identification rules of the world of materials; suitability for drinking water only as the manufacturer’s approval per system; no standard texts, no analysis ranges, no resistance data for media. Not legal advice.