Copper press fittings
Entry in Joining methods · Updated · Written by the Know Your Pipes editors from the sources listed under References
Copper press fittings are copper or copper-alloy fittings with a rubber sealing element inside each socket; a powered press tool crushes the socket onto copper tube to make a permanent, flame-free joint.[2] They are an alternative to soldered sweat joints on copper water lines.
ASME B16.51, Copper and Copper Alloy Press-Connect Pressure Fittings, sets requirements for cast copper alloy, wrought copper and wrought copper alloy press fittings used with hard-drawn ASTM B88 copper water tube.[1] The current edition is dated 2021, and it rates the press-connect system for a maximum of 200 psi from 32°F to 200°F.[1]
1 How the joint works
The seal comes from the elastomer ring rather than from the metal. ASTM B1029-24 is a standard practice describing making permanent press-connect joints by compressing that elastomeric sealing element between copper tube and fitting.[2] Larger fittings may add a stainless steel grip ring and a separator ring behind the seal; one maker uses both in its 2 1/2 in to 4 in sizes.[3]
Tube preparation is part of the maker's instructions rather than a separate skill. In one maker's sheet the tube is cut square without being deformed, deburred inside and out, checked for a clean and undamaged sealing element, and marked for insertion depth; oils and lubricants are not allowed.[4] The depth mark is meant to stay visible after pressing so an inspector can see the tube went fully into the fitting.[4]
| Tube size | Minimum insertion depth |
|---|---|
| 1/2 in | 3/4 in |
| 3/4 in | 7/8 in |
| 1 in | 7/8 in |
| 1 1/4 in | 1 in |
| 2 in | 1 9/16 in |
The depths come from one maker's product instructions for 1/2 in to 4 in fittings.[4] That sheet sets a minimum distance between neighboring fittings from 1 1/4 in up, so the tool jaws can close fully.[4]
2 Tube, ratings and listings
One maker's press fittings accept ASTM B88 tube in types K, L and M; see copper pipe types K, L and M.[3] Its annealed soft copper is limited to 1/2 in to 1 1/4 in, while hard-drawn tube may be used from 1/2 in to 4 in.[3]
That maker lists an operating pressure of up to 300 psi, a test pressure of up to 600 psi, and an operating temperature of 0°F to 250°F, with listings that include NSF/ANSI 61, NSF/ANSI 372 and ASME B16.51.[3] Its approved uses include hot and cold drinking water, hydronic heating, chilled water and compressed air, and it allows burial when the local inspector approves first.[3] Ratings and approved uses differ between makers, so the product data sheet governs a given job.
3 Unpressed-joint detection and limits
Some press fittings are designed so that a fitting left unpressed can be identified during the system pressure test.[3] One maker states that this feature is not a replacement for the pressure tests required by local codes and standards.[4]
Press fittings are designed to be installed by licensed and trained plumbing and mechanical professionals, and one maker says installation by non-professionals may void its warranty.[3] Supply houses list press fittings by size and sealing element; PlumbingSupplyAndMore's water press fittings category (PlumbingSupplyAndMore has the same owners as this reference) is one example. A homeowner emergency repair is a different case, covered under push-fit fittings.
Video
A fitting maker's training clip on what is inside a copper press fitting and how the press tool locks it on. From the Viega LLC channel; nothing loads from the video site until you press play.
See also
- Copper pipe types K, L and MThe three wall grades of copper water tube under ASTM B88, how to tell them apart and where each is normally used.
- Soldered (sweat) jointsHow a sweat fitting is soldered to copper tube by capillary action, which solders are lawful for drinking water, and how brazing differs.
- Push-fit fittingsFittings that seal by pushing tube into an O-ring and locking device; covered by ASSE 1061 for PEX, copper, CPVC and PE-RT.
- PEX crimp ringsCopper rings squeezed around PEX over a ribbed insert fitting; made to ASTM F1807 or F2159 and checked with a go/no-go gauge.
- PEX clamp (cinch) ringsStainless steel bands with a tab, closed by a ratcheting tool over PEX insert fittings; an ASTM F2098 alternative to copper crimp rings.
- PEX expansion fittingsFittings joined by stretching PEX tubing and a ring, then letting the tube shrink back onto the fitting; ASTM F1960 and F2080.
References
- ASME, "B16.51 – Copper and Copper Alloy Press-Connect Pressure Fittings" (2021) — asme.org
- ASTM International, "ASTM B1029-24 Standard Practice for Making Press-Connect Joints with Copper and Copper Alloy Tube and Press Fittings" (2024) — store.astm.org
- Viega, "Viega ProPress Fitting Systems: System Data, SD-PP" — viega.us
- Viega, "Product Instructions: Viega ProPress 1/2 in to 4 in Fittings, PI-PP 531438" — viega.us