Water supply lines are the pipes that bring fresh water from the source into a home and out to each faucet. In every house, the main line usually splits inside: one part goes directly to cold-water taps, while the other goes to the water heater and then to hot-water taps. From these main hot and cold lines, even smaller pipes branch off to reach every sink, shower, and appliance.
Before you begin, plan carefully. Know where each pipe will run and which type of pipe you will use for your house plumbing. First, shut off the main water valve (usually near the street or meter) so that water flow stops. Open a faucet to make sure the water is off and drain the pipes. Then check your local building codes (the rules set by your town) to see what pipe sizes and materials are allowed. For example, some codes require the main water pipe to be at least 3/4 inch wide or only allow certain approved pipe types.
Choosing Pipe Materials
Water supply lines can be made from different materials. The most common pipes are:
-
PEX (flexible plastic) – PEX is a bendable plastic tubing that is quick to install. It is also much cheaper than copper (about one third the price). PEX tubing often comes color-coded: red tubing for hot water and blue for cold water. Because it bends easily, PEX can go around corners without many fittings. To join PEX pieces, you use special clamps or push-fit connectors.
-
PVC (hard plastic) – PVC is a rigid plastic pipe that is light and inexpensive. To join PVC pipes, you need to glue them with PVC cement. The glue makes a strong, waterproof joint, but it also means the joint is permanent (to change it you’d have to cut the pipe out). Some areas do not allow PVC for drinking water lines. (Always check your codes.)
-
Copper (metal) – Copper pipes are very durable and long-lasting. They handle high heat and pressure well. However, joining copper pipes requires soldering (using a torch and solder). This can be tricky for a beginner. Copper pipe is more expensive and heavier than PEX or PVC, but it is proven and can be recycled later.
For most DIY home projects, PEX or PVC is easiest for a beginner. Copper is best if you want the strongest material and don’t mind the extra work of soldering.
Besides the pipes, gather fittings (elbows, tees, reducers) that match your pipe type, plus shutoff valves and faucets as needed. Get some plumber’s (Teflon) tape too: it is a white thread-seal tape you wrap on threaded connectors to prevent leaks.
Planning Your Water Line Installation
Careful planning makes the job go smoothly:
-
Turn off the main water valve: Locate and close the main shut-off valve for your house. This stops the water supply. Check by turning on a faucet to confirm the water is off.
-
Drain the pipes: Open one faucet on the lowest floor and one on the highest floor to let any remaining water flow out. This avoids a surprise spill when you cut a pipe.
-
Follow the code: Your city or county might have rules about plumbing (building codes). For example, codes often say the main water pipe must be at least 3/4 inch in diameter. Some areas only allow copper or other approved materials for water lines. Read the local rules or ask an expert to be sure.
-
Plan the route: Sketch how the pipes will run from the main line to each bathroom, kitchen sink, washing machine, etc. Try to keep pipes as straight as possible. Every bend can slow water flow, so reducing unnecessary turns will keep the water moving well.
-
Measure twice, cut once: Measure the needed lengths for each pipe run, adding a little extra. Double-check your measurements before cutting.
Step-by-Step Installation Guide
-
Cut Pipes to Length: Using a pipe cutter or fine-toothed saw, cut each pipe to the length you need. A pipe cutter (for copper or PEX) gives a straight cut. If you use a saw, support the pipe so it doesn’t wobble. Clean any rough edges with sandpaper or a deburring tool.
-
Dry-Fit the Pipes: Before making permanent joints, assemble the pipes and fittings without glue or solder. This is called dry-fitting. Check that everything lines up and each pipe reaches its fitting with a little room to spare. Adjust the lengths if needed.
-
Make the Joints: Now connect the pipes permanently.
-
For PVC: Apply PVC primer and then PVC cement to the outside of the pipe end and inside the fitting. Push the pipe fully into the fitting and hold for a few seconds. The glue will set and make a solid seal.
-
For Copper: Slip flux onto the outside of the pipe and into the fitting. Join the pipe and fitting together. Heat the joint evenly with a propane torch, then touch solder wire to the joint. The solder will melt and be drawn into the seam, creating a watertight seal. Make sure the pipe and fitting are clean (polished) before heating.
-
For PEX: Push the PEX pipe fully into a PEX fitting (plastic or metal). If using a clamp-style fitting, slide a metal clamp ring over the pipe first, then push the pipe into the fitting. Use a crimp tool to tighten the clamp ring onto the fitting. If using a push-fit or threaded PEX fitting, simply push or screw the pieces together. (No glue or solder is needed with PEX.)
-
-
Wrap Threaded Connections: For any threaded fittings (like metal valves or adapters), wrap the male threads with plumber’s tape before screwing them together. Wrap the tape clockwise so it doesn’t unwind as you tighten. This helps seal the threads and prevent leaks.
-
Secure the Pipes: Use brackets or pipe clamps to attach the new pipes to wall studs or joists. Secure the pipes every few feet and especially near any turns or fittings. This stops the pipes from moving, rattling, or bursting if water pressure changes.
-
Turn On Water and Test: Slowly open the main valve to refill the system. Check each joint and fitting closely for leaks as the water comes in. You might hear air escaping from the pipes — that’s normal as they fill up. Then open each faucet one by one to let air out of the lines. Keep a cloth or bucket under each connection. If you see any drips or wet spots, tighten the fitting or redo that joint. Watch for a few minutes to be sure everything is leak-free.
Final Tips and Common Issues
-
Always clean and remove burrs from pipe ends before joining them. Dirt or rough edges can cause leaks.
-
Plumber’s tape: When wrapping threaded joints, use 2–3 tight wraps of tape on the threads, smoothing it down as you go.
-
Different metals: If you must connect copper pipe to a steel or brass fitting, use a brass slip coupling or dielectric union to separate the metals. Direct contact between copper and steel can corrode over time.
-
Leaky valves: If a shut-off valve leaks, try tightening the packing nut first. If that fails, you may need to replace the valve or redo the connection (especially on glued PVC joints).
-
Label new lines: Mark any new shut-off valves or pipes so you know which fixture they serve (e.g. “Kitchen Sink”, “Bathroom Shower”). This makes future maintenance much easier.
By following these steps and tips, you can install or replace water supply lines in your home. Take your time and work safely, always double-checking your connections. With the right pipes (copper, PEX, or PVC) and careful fitting, your home’s plumbing will deliver water to every tap the way it should.
Also read:
