1. The Three Types (ASTM B88)
| Type | Marking | Wall (1/2" example) | Best For |
|---|---|---|---|
| K | Green | 0.049" (1.24 mm) | Underground, high pressure, harsh exposure |
| L | Blue | 0.040" (1.02 mm) | Standard residential/commercial hot & cold lines |
| M | Red | 0.028" (0.71 mm) | Economical residential, normal pressure |
Type K is the strongest per unit wall (highest working pressure); Type M is the cheapest and lightest but not for burial, high pressure or corrosive soil. Metric sizes per EN 1057 use a different wall series.
2. Material
Water tube is DHP copper (C12200, phosphorus-deoxidized, high residual phosphorus): the phosphorus prevents hydrogen embrittlement during brazing and improves corrosion resistance in water. ASTM B88 covers seamless tube; B280 is the A/C&R standard (thinner walls).
3. Selection Factors
Water pressure: high-rise or high-pressure systems → Type L or K; typical residential → M or L;
Location: buried/underground or exposed to corrosive soil → Type K (thicker wall + sleeving where required);
Budget: M is most economical; L balances cost and durability;
Codes: local plumbing codes (IPC/UPC) may mandate minimum type by application;
Water quality: copper suits pH ~5-9; aggressive soft/acidic water needs corrosion control (pH adjustment or treatment).
4. Joining Methods
Soldering with lead-free solder (ASTM B32 / RoHS) - standard for water;
Brazing with BCuP filler for high-temperature service;
Press-fit and push-fit fittings - fast, no flame, code-approved;
Compression fittings for service valves and appliance connections.
5. Sizing Note
Nominal sizes (1/2", 3/4", 1") refer to nominal OD (e.g. 1/2" = 0.625" OD ≈ 15.9 mm); internal diameter varies by type - calculate flow capacity on the actual ID of the chosen type.
