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BuyCopper Tube Pressure Rating Calculator
Tube rating, joint rating and the one that actually governs — at your real service temperature, from the Copper Development Association tables
Ask what half-inch Type L copper is rated for and you will usually be told something like twelve hundred psi. That is the tube. It is also almost never the number that matters, because the Copper Tube Handbook says plainly that “in designing a system, tube, fitting and joint ratings must be considered collectively, because the lower of the ratings (tube, fitting or joint) will govern the maximum installation design pressure” — and then, two sentences later, “in soldered tubing systems, the rated strength of the joint often governs design.” On that same half-inch line, soldered with 50-50 at 200°F, the joint is rated 100 psi. Not 1,242. A hundred. This page puts both numbers side by side at the temperature you are actually running, tells you which one governs and by how much, and does it from the published tables rather than from a rule of thumb.
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Making the joint the table assumes
Every rating on this page is for a joint made properly: cleaned to bright metal, fluxed, heated evenly, and filled by capillary action all the way round. A joint that is only half filled is not a weaker version of the rating — it is an unknown. These are the tools that put a real joint on the end of the tube and then prove it held.
Bernzomatic TS8000 Trigger-Start Torch
- Enough heat for 1 in. and larger without cooking the fitting
- Instant on-off, which is how you keep heat off a nearby valve seat
- Takes MAP-Pro for the faster, hotter work brazing temperatures need
Oatey Safe‑Flo Lead‑Free Solder
- Lead-free, so it stays inside the 0.2 percent Safe Drinking Water Act limit
- The potable-water answer where 50-50 is on the page only as history
- Paired with the right flux, it is what the 95-5 column of the table describes
Water Pressure Test Gauge
- Reads the static pressure this page checks the rating against
- Lazy hand catches the overnight thermal expansion spike you never see
- Hose thread, so it goes on a sillcock or a laundry bib in seconds
Copper Tube & Fitting Brush Set
- Bright metal inside the cup and outside the tube, which is what capillary action needs
- The single most common cause of a joint that will not take solder
- Covers the 1/2, 3/4 and 1 in. sizes most of this table lives in
RIDGID Close‑Quarters Tubing Cutter
- Square cut and full socket depth, which is where the joint area comes from
- Deburring matters: a raised burr is a velocity problem, not just a flow one
- Works in the joist bay where a hacksaw cannot
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Three ratings, and only the smallest one counts
The Copper Tube Handbook states the design rule in one sentence, and it is the reason this page exists:
“In designing a system, tube, fitting and joint ratings must be considered collectively, because the lower of the ratings (tube, fitting or joint) will govern the maximum installation design pressure.”
Most published “copper pipe pressure rating” figures are the first of those three only. Here is what that looks like on a ½ in Type L line, which is the single most common run in a house, at four temperatures:
| Service temperature | Tube, drawn | 50-50 solder joint | 95-5 solder joint | Brazed joint |
|---|---|---|---|---|
| 100°F | 1,242 psi | 200 psi | 1,090 psi | 722 psi |
| 150°F | 1,242 psi | 150 psi | 625 psi | 613 psi |
| 200°F | 1,242 psi | 100 psi | 505 psi | 589 psi |
| 250°F | 1,242 psi | 85 psi | 270 psi | 577 psi |
Read the 50-50 column against the tube column. At 200°F the tube is rated more than twelve times what the joint is rated. Anyone quoting 1,242 psi for that line is describing a pipe that does not exist in isolation — it has fittings on it. The handbook says so directly a few lines later: “In soldered tubing systems, the rated strength of the joint often governs design.”
Notice also that the brazed column is lower than the 95-5 column at 100°F and higher at 250°F. That is not an error. A brazed joint is rated as the annealed tube, so it starts from a lower number than hard drawn tube but it barely falls with temperature, while solder falls off a cliff. Which joint is “stronger” depends entirely on how hot the line runs.
Where the tube rating comes from
The tube numbers are not measured. The handbook is explicit that they are calculated, using the formula from the ASME Code for Pressure Piping:
P = 2S(t − C) ÷ (D − 0.8(t − C))
where P is the allowable pressure in psi, S is the maximum allowable stress in tension in psi, t is the minimum wall thickness, D is the maximum outside diameter, and C is a constant. The handbook then removes the constant: “For copper tube, because of copper’s superior corrosion resistance, the B31 code permits the factor C to be zero”, leaving
P = 2S·tmin ÷ (Dmax − 0.8·tmin)
Everything about the temperature behaviour of copper tube falls out of the one term S, which is printed in the column headers of the rating tables themselves:
| Temperature | 100°F | 150°F | 200°F | 250°F | 300°F | 350°F | 400°F |
|---|---|---|---|---|---|---|---|
| Annealed (soft) | 6,000 | 5,100 | 4,900 | 4,800 | 4,700 | 4,000 | 3,000 |
| Drawn (hard) | 10,300 | 10,300 | 10,300 | 10,300 | 10,000 | 9,700 | 9,400 |
Two things are worth pulling out of that table. First, hard drawn tube is allowed about 1.7 times the stress of the same tube annealed at room temperature — that is the cold working, and it is why a rigid length out-rates a coil. Second, the drawn allowable is flat to 250°F and then starts to drop, while the annealed allowable sheds 15 percent between 100 and 150°F alone. Because P is directly proportional to S, every rating in the tables scales exactly with these numbers; that property is what this page uses to check its own transcription.
A useful sanity check you can do yourself. Take any published rating, put it back through the formula, and solve for the wall thickness it implies. For ½ in Type L annealed at 100°F, 722 psi implies t = 0.0359 in — about 90 percent of the 0.040 in nominal wall, which is exactly the ASTM B88 wall tolerance. Do it across all 57 published rows and it comes out between 88 and 91.5 percent every time. The formula, the stress values and the dimensions are all consistent with each other.
Why brazing makes the tube weaker
This is the single most counter-intuitive item in the handbook, and it catches experienced people. Brazing produces a joint that is far stronger than solder — and it reduces the rating of the tube it is on.
The reason is temper. Hard drawn tube gets its strength from cold working. Brazing filler metals melt at or above 1,100°F, and heating copper to that temperature anneals it. The handbook spells out the consequence twice, once as a footnote on every drawn column and once in the body text:
“When brazing or welding is used to join drawn tube, the corresponding annealed rating must be used.”
“When brazing, use the ratings for annealed tube found in Tables 14.3a-e as brazing softens (anneals) the tube near the joints (the heat affected zone).”
“When brazing, use the ratings for annealed tube found in Tables 14.3a-e as brazing softens (anneals) the tube near the joints (the heat affected zone).”
So on that same ½ in Type L line at 100°F, the tube drops from 1,242 psi drawn to 722 psi once you braze it — a 42 percent reduction in the tube rating, bought in exchange for a joint that is no longer the weak point. The calculator above applies this automatically: select brazing and it switches the tube to its annealed column and tells you it has done so.
The same footnote is the reason the handbook publishes annealed rows for Type M at all, even though “Types M and DWV are not normally available in the annealed temper”. Those rows exist precisely so you have a number to use when drawn Type M gets brazed.
The four solders are not interchangeable
Four solder alloys appear in the joint table and they are startlingly different. Same tube, same fitting, same 1 in size, pressure fittings:
| Alloy | 100°F | 150°F | 200°F | 250°F | Saturated steam | Potable water? |
|---|---|---|---|---|---|---|
| Sn50, 50-50 tin-lead | 200 psi | 150 psi | 100 psi | 85 psi | 15 psi | No — lead |
| Sb5, 95-5 tin-antimony | 1,090 psi | 625 psi | 505 psi | 270 psi | 15 psi | Yes |
| Alloy E | 710 psi | 475 psi | 375 psi | 320 psi | 15 psi | Yes |
| Alloy HB | 1,035 psi | 710 psi | 440 psi | 430 psi | 15 psi | Yes |
| Brazing (≥ 1,100°F filler) | Rated as the annealed tube — see Table 14.3 | 120 psi | Yes | |||
50-50 tin-lead is five to ten times weaker than the lead-free alloys that replaced it, which is worth knowing when you are evaluating an existing building rather than specifying a new one. It is also illegal on potable water, and the handbook carries the statute: “The Safe Drinking Water Act Amendment of 1986 prohibits the use in potable water systems of any solder having a lead content in excess of 0.2%.”
The saturated steam row is the one that ends arguments. Every solder — including the good ones — is rated 15 psi at saturated steam temperature. Brazing is rated 120 psi. Soldered copper is not a steam material.
Alloy E and Alloy HB are trade designations, not a specification you can buy to by name alone. They are ASTM B32 alloy designations as the handbook uses them. When you buy lead-free solder, check what the roll actually says and match it to the column you used — do not assume every lead-free solder performs like Alloy HB.
Size bands: why ½ in and 1 in share a rating
The tube table gives a rating for every size. The joint table does not — it gives one rating per band, and the bands are wide:
| Band | Sizes it covers | 95-5 at 150°F, pressure fitting | 95-5 at 150°F, DWV fitting |
|---|---|---|---|
| 1 | ⅛ through 1 in | 625 psi | not published |
| 2 | 1¼ through 2 in | 485 psi | 225 psi |
| 3 | 2½ through 4 in | 405 psi | 185 psi |
| 4 | 5 through 8 in | 375 psi | 190 psi |
| 5 | 10 through 12 in | 285 psi | not published |
Joint rating falls as size rises, because the pressure is acting on a bigger area while the solder film stays the same thickness. Within a band, though, the published figure is flat — a ⅜ in joint and a 1 in joint carry the same number.
The DWV column is the other thing to notice. Drainage fittings have shallower sockets and less joint area, and they are rated at roughly half the pressure fitting figure. Below 1¼ in and above 8 in the handbook publishes no DWV pressure rating at all, and 50-50 solder in a DWV fitting has no 250°F rating. A drainage fitting is not a cheap pressure fitting.
Press, push and groove: the no-flame joints
Mechanical joints are rated differently again — a flat pressure ceiling with a size range and a temperature range, rather than a curve:
| Joint type | Sizes | Pressure | Temperature |
|---|---|---|---|
| Press-connect, general piping | ½ – 4 in | 0 – 200 psig | 0°F – 250°F |
| Press-connect, high-pressure HVACR | ¼ – 1⅛ in | 0 – 700 psig | −25°F – 300°F |
| Push-connect | ½ – 2 in | 0 – 200 psig | 0°F – 250°F |
| Roll-groove, Types K & L | 2 – 8 in | 0 – 300 psig | −30°F – 250°F |
| Roll-groove, Type M | 2 – 4 in 5 – 8 in | 0 – 250 psig 0 – 200 psig | −30°F – 250°F |
A 200 psi press fitting looks weak next to a 1,090 psi soldered joint, and in a narrow sense it is. In practice it is 200 psi flat all the way to 250°F, where 95-5 solder has fallen to 270 psi and 50-50 to 85. For a domestic system at 60 to 80 psi, every one of these is ample; the rating is rarely the reason to choose between them.
The footnote matters more than the number here. The handbook attaches a standing instruction to this table: “Actual pressure/temperature ranges should be confirmed based upon the specific manufacturer’s fittings being utilized.” Press and push systems are proprietary. The generic figure above is a starting point; the fitting maker’s published data is what governs, and it is often different — sometimes higher, and for some seal materials and some fluids a good deal lower.
Burst pressure is not a design figure
The handbook publishes actual burst pressures alongside the rated ones, and invites the comparison: “Compare the actual values in Table 14.5 with the rated working pressures found in Tables 14.3a, 14.3b and 14.3c. The very conservative working pressure ratings give added assurance that pressurized systems will operate successfully for long periods of time.”
| ½ in tube | Rated at 100°F | Actual burst | Ratio |
|---|---|---|---|
| Type K, drawn | 1,534 psi | 9,840 psi | 6.4× |
| Type L, drawn | 1,242 psi | 7,765 psi | 6.3× |
| Type M, drawn | 850 psi | 6,135 psi | 7.2× |
| Type L, annealed | 722 psi | 3,885 psi | 5.4× |
Those burst figures are real test results — “averages of three certified tests performed on each type and size of water tube… No burst pressure in any test deviated from the average by more than 5 percent” — taken on tube at or near minimum wall. The margin between rated and burst is five to seven times on the tube, which is the handbook’s point about unpredictable pressure surges.
None of that margin belongs to the joint. Table 14.5 is a tube test. The solder joint that governs your actual line has no published burst figure here at all, and the comfortable 6× margin on the pipe tells you nothing about it. Burst pressure is useful for understanding how conservative the tube rating is. It is not a number to design to, and it is not a reason to run a line above its governing rating.
What this page will not tell you, and why
- A rating between the published temperatures. The tables are given at fixed steps, and the handbook publishes no interpolation rule. This page rounds your temperature up to the next step, which is conservative, rather than inventing a value between them.
- Your specific fitting’s rating. For press, push and grooved systems the manufacturer governs, and the handbook says so. The same applies to valves, which frequently have the lowest rating in the whole assembly and are not in these tables at all.
- Hydrostatic test pressure or duration. That is a plumbing code question, not a CDA one, and no verified code text was available for this build.
- Water hammer surge pressure. Transient pressure from a quick-closing valve sits on top of working pressure and can be several times it. Calculating it needs a pressure-wave speed for the specific pipe, which is a published figure for steel and is not one this page can source for copper. It is not estimated here.
- Thermal expansion force. A copper line restrained between two fixed points and heated develops stress that has nothing to do with internal pressure. Different calculation, different failure mode.
- Pressure drop, velocity, or hanger spacing. All in the same handbook, all different questions.
- Whether your local code allows it. Codes restrict tube types, solders and joining methods beyond anything in these tables. Type M is prohibited for some uses in some jurisdictions regardless of its rating.
Frequently asked questions
What is the pressure rating of 1/2 inch Type L copper pipe? The tube itself is rated 1,242 psi drawn or 722 psi annealed at 100°F, from CDA Table 14.3b. That is almost never the answer you want, because the installed line also has joints, and the Copper Tube Handbook states that the lower of the tube, fitting and joint ratings governs the maximum installation design pressure. The same half-inch line soldered with 95-5 tin-antimony is rated 1,090 psi at 100°F and 505 psi at 200°F; soldered with 50-50 tin-lead it is 200 psi at 100°F and 100 psi at 200°F. The joint governs in every one of those cases.
Does copper pipe lose pressure rating as it gets hotter? Yes, and the tube and the joint lose it at very different rates. The tube rating is proportional to the maximum allowable stress S, which for hard drawn tube is flat at 10,300 psi all the way to 250°F and only then begins to fall, reaching 9,400 psi at 400°F. Annealed tube drops much sooner, from 6,000 psi at 100°F to 5,100 psi at 150°F. Soldered joints fall far faster than either: 95-5 tin-antimony on a 1 in line goes from 1,090 psi at 100°F to 270 psi at 250°F, a drop of three quarters.
Why is brazed copper rated lower than soldered copper at room temperature? Because brazing anneals the tube. Brazing filler metals melt at or above 1,100°F, and heating hard drawn copper to that temperature removes the cold work that gave it its strength. The handbook instructs that when brazing or welding is used to join drawn tube, the corresponding annealed rating must be used. A brazed joint is rated as strong as the annealed tube, which on half-inch Type L at 100°F is 722 psi against 1,242 psi for the same tube hard drawn. At higher temperatures the comparison reverses, because the brazed rating barely falls while solder collapses.
Can I still use 50-50 solder? Not on potable water. The handbook carries the statutory restriction: the Safe Drinking Water Act Amendment of 1986 prohibits the use in potable water systems of any solder having a lead content in excess of 0.2 percent, which excludes 50-50 tin-lead. It remains in the rating tables because it is still used in non-potable service and because a great deal of it is still installed in older buildings, where knowing that a joint is rated 100 psi rather than 500 changes what you can safely do to the system.
What is the difference between Type K, L and M copper? Wall thickness, and nothing else that matters dimensionally. All three share the same outside diameter at a given nominal size, which is why the same fittings fit all of them. Type K has the thickest wall and the highest rating, Type L is the general plumbing and hydronic standard, and Type M is thinnest. On half-inch drawn tube at 100°F the ratings are 1,534, 1,242 and 850 psi respectively. Type M is restricted or prohibited for certain uses by some local codes regardless of its calculated rating.
How is the copper tube pressure rating calculated? From the ASME B31 Code for Pressure Piping formula, which the handbook prints as the allowable pressure equalling twice the maximum allowable stress times the minimum wall thickness, divided by the maximum outside diameter minus eight tenths of the minimum wall thickness. A constant C appears in the general form, but for copper tube the B31 code permits C to be zero because of copper’s corrosion resistance. The maximum allowable stress depends on temper and temperature and is printed in the column headers of the rating tables themselves.
Why do the joint ratings jump in steps instead of changing with every size? Because CDA Table 14.4a publishes joint ratings in five nominal size bands rather than per size: one-eighth through 1 in, 1¼ through 2 in, 2½ through 4 in, 5 through 8 in, and 10 through 12 in. A three-eighths inch joint and a 1 in joint carry the same published figure. The rating falls as the bands get larger because internal pressure acts over a greater area while the solder film in the socket stays about the same thickness.
Can soldered copper be used on steam? Not meaningfully. Every solder alloy in the handbook table, including the lead-free ones, is rated 15 psi at saturated steam temperature. Brazed joints are rated 120 psi at saturated steam. The eight-fold difference is why steam and high-temperature work is brazed rather than soldered, and the 15 psi figure is low enough that it rules soldered copper out of most steam service entirely.
Are press fittings weaker than soldered joints? At room temperature the published figures say yes: general piping press-connect is rated 0 to 200 psig against 1,090 psi for a 95-5 soldered joint on a 1 in line. But the press rating is flat across its whole temperature range to 250°F, where 95-5 has dropped to 270 psi and 50-50 to 85 psi. For ordinary domestic and commercial water at 60 to 80 psi both are far beyond what the system asks. The handbook also attaches the instruction that actual press and push fitting ranges must be confirmed with the specific manufacturer, so the generic figure is a starting point rather than the final answer.
What does the burst pressure tell me? How conservative the tube rating is, and nothing more. The handbook publishes actual burst pressures as averages of three certified tests per type and size, taken on tube at or near minimum wall, and they run five to seven times the rated working pressure. That margin is the handbook’s stated reason for confidence that systems will tolerate unpredictable pressure surges. It is a destructive test result, it applies to the tube and not to the joint that usually governs, and it is never a figure to design to.
Can I use a DWV fitting on a pressure line? No. Drainage fittings have shallower sockets and less joint area, and CDA rates them separately and much lower — roughly half the pressure-fitting figure where a rating is published at all. Below 1¼ in and above 8 in no DWV pressure rating is published, and 50-50 solder in a DWV fitting has no 250°F rating. The drainage ratings use ASME B16.29 and B16.23 fittings, a different standard from the B16.22 and B16.18 pressure fittings.
My system runs at 130 degrees F. Which table row applies? The published tables step at 100, 150, 200 and 250°F for joints and add 300, 350 and 400°F for tube, and CDA publishes no rule for interpolating between the steps. The conservative approach, and the one this page takes, is to use the next step above your actual temperature — so 130°F is read on the 150°F row. That gives up a little capacity you may genuinely have, in exchange for never over-stating the rating.