How to Drain Water Lines in a House

A gate valve.
A gate valve. (Image: water valve image by Wayne Abraham from Fotolia.com)

Most plumbing projects begin with a simple task that prevents much damage and weeping: draining the water from your home’s pipe system. Whether you are replacing a shower head, installing an outdoor hose faucet or re-piping an entire portion of your home, draining the water from the system ensures that you won’t drench yourself or flood your home. Master this simple procedure and you’ll be prepared to deal with both plumbing repairs and emergencies.

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Locate the main water supply shutoff for your home. Because building standards and practices change over time, there is no uniform location for a water supply shutoff. A majority of single-family residences feature a main water supply shutoff in one of two places: attached to or near a water meter that protrudes from a wall along the building’s exterior perimeter, or inside an irrigation box near the property’s perimeter. Search for the latter on the street-facing side of your property--this is where utility easements usually exist.

Shut off the main water supply. If a box holds your main shutoff, open the box. The shutoff valve will feature a knob or handle. Turn the knob or handle in the counterclockwise direction. Don’t worry if you’re in doubt--most shutoffs feature arrows indicating on and off directions. If the valve is sticky, use the rag to grip and turn.

Open all faucets and flush all toilets. With the water supply cut off, you must “bleed” remaining water held within the pipes. Visit every sink, toilet and bath fixture, fully open them and allow the water to drain. If your task requires draining a water heater, you’ll have to follow manufacturer’s instructions for draining. (This usually involves attaching a garden hose to the heater and opening a valve.)

Allow water to run until it becomes a slow drip. After the toilets have drained their tanks, flush them one more time to empty the bowls. When the duration between drips reaches four to five seconds, you can safely remove fittings and fixtures for repair.

Tips & Warnings

  • Older or custom homes might require special tools for tightening and loosening shutoff valves. If you can't manipulate your valve by hand, take a picture of it and show it to the sales staff at a plumbing supply house--they might have the right tool for your job.
  • Removing a faucet or supply line before shutting off the water supply may cause flooding (or at least give you a good drenching).
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