Plumbing Supply Lines & Valves Guide: A Reference for Contractors and DIY

Supply lines and valves are the unglamorous but critical components that connect your fixtures to the water supply. A leaking supply line or failed shut-off valve can cause thousands of dollars in water damage. This guide covers the types, materials, and best practices that contractors and DIYers need to know.

Supply Line Types

Braided Stainless Steel

The modern standard. Flexible stainless steel braid over a rubber or polymer inner hose. Easy to install (hand-tighten + 1/4 turn with pliers), available in standard lengths, and burst-resistant. Used for faucets, toilets, dishwashers, and ice makers. Replace every 8-10 years as a precaution.

Polymer / PEX

Cross-linked polyethylene tubing. Flexible, freeze-resistant, corrosion-proof. Used for whole-house repiping and long runs. Color-coded (red = hot, blue = cold, white = either). Connects with crimp, clamp, or push-fit fittings. Cannot be used for outdoor/UV-exposed applications.

Copper

The traditional choice. Rigid (Type L or M) or soft (for bending). Extremely durable, long lifespan (50+ years). Requires soldering or compression fittings. Higher material and labor cost. Still preferred for main lines and exposed applications.

CPVC

Chlorinated polyvinyl chloride. Rigid plastic tubing rated for hot and cold water. Uses solvent cement connections. Less expensive than copper. Common in southern US construction.

Shut-Off Valves

Quarter-Turn Ball Valves

The recommended type for all new installations. A 90-degree turn fully opens or closes the valve. Reliable, low failure rate, works even after years of non-use. Available in brass or CPVC. Always specify quarter-turn ball valves for fixture shut-offs.

Multi-Turn Gate/Globe Valves

Older technology. Requires multiple turns to open/close. Prone to failure after years of non-use (the stem packing dries out and the valve seizes or leaks). If you have these, plan to replace them during your next renovation.

Compression vs Solder vs Push-Fit

Sizing Reference

• Faucet supply lines: 3/8" OD compression x 1/2" FIP — standard for kitchen and bathroom faucets
• Toilet supply lines: 3/8" OD compression x 7/8" ballcock — standard toilet connection
• Main shut-off: 3/4" or 1" — sized to match your main water line
• Dishwasher supply: 3/8" OD compression — connects to the hot water line under the sink
• Ice maker: 1/4" OD compression — small line to the refrigerator

Brass Fittings Reference

• Couplings — Join two pipes in a straight line (same or different sizes with reducing couplings).
• Elbows — 90-degree or 45-degree turns. Available in street (male x female) or standard (female x female).
• Tees — Branch a single line into two. Reducing tees allow different branch sizes.
• Adapters — Convert between thread types (MIP, FIP) or pipe types (compression to solder, PEX to copper).
• Nipples — Short pre-cut threaded pipe sections for close connections.

Pro Tips

• Always use Teflon tape (3-5 wraps clockwise) or pipe dope on threaded connections.
• Replace all supply lines when renovating — they're cheap insurance against water damage.
• Install quarter-turn ball valves at every fixture so you can isolate problems quickly.
• Label your main shut-off valve location — every household member should know where it is.

Our Recommendation

For fixture connections, braided stainless supply lines with quarter-turn ball valve stops are the standard. For repiping, PEX with crimp or expansion fittings offers the best combination of cost, durability, and ease of installation. We stock supply lines, valves, fittings, and adapters from top brands for both contractors and DIYers.

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