To drain pipes for winter, the main water supply must be shut off, every faucet opened from top to bottom, toilets flushed dry, and remaining water forced out with compressed air—the only way to stop ice from bursting your plumbing.
The fix takes one afternoon and a few tools, but skipping even one step leaves water trapped where it freezes and splits. This is the full procedure for standard US homes with copper, PEX, or CPVC pipes, verified against plumbing sources and tested by homeowners in freezing climates.
Step 1: Shut Off the Main Water Supply
Find the main shutoff valve—usually near the water meter in a basement, utility room, or outside by the curb. Turn a gate valve clockwise until it stops; move a ball valve’s lever 90 degrees to the right so it’s perpendicular to the pipe. If the main valve inside the house is inaccessible, shut off water at the street valve outside.
Step 2: Drain Every Fixture From Top to Bottom
Open all faucets—both hot and cold—starting on the top floor and working down to the lowest level. Let them run until only a drip or air sputter remains, then leave them open. Flush every toilet and hold the handle down to empty the tank and bowl fully. Remove tank covers to pour out leftover water. Open all hose bibs (sillcocks) and disconnect garden hoses; a hose left attached can trap water that backs up into the wall pipe and freezes.
Step 3: Drain the Water Heater and Appliances
Turn off electric power or gas to the water heater before draining—firing an empty tank destroys the heating elements or burner. Connect a garden hose to the drain valve at the tank’s bottom, run it to a floor drain or outdoors, and open the pressure relief valve on top to let air in while the tank empties. Run the dishwasher’s short cycle to clear its line, then run both hot and cold cycles on the washing machine. Open the shutoff valves under each toilet so compressed air can reach the supply tubing later.
Read our tested roundup of drain pipe winterizing gear
Step 4: Blow Out Residual Water With an Air Compressor
Attach an air compressor to an open faucet—usually the lowest one or a basement hose bib. Blow air at about 70 psi; never exceed this pressure, or you’ll damage joints and valves. Apply short bursts to the drain, then open each faucet one at a time to force out remaining water. This Old House’s guide calls this the most critical step for avoiding trapped water.
| Fixture | What To Do | Why It Matters |
|---|---|---|
| Main water valve | Shut off, leave all faucets open | Stops new water entering; open taps prevent vacuum lock |
| Water heater | Disconnect power/gas, open drain valve + pressure relief | Empty tank won’t crack; dry element stays safe |
| Toilets | Flush, hold handle, tank covers off | Stagnant water in bowl freezes and cracks porcelain |
| Hose bibs | Open, detach all hoses | Ice in a connected hose travels back into the wall pipe |
| Air compressor | 70 psi max, blow each faucet individually | Force last drops out of low spots and PEX bends |
| Dishwasher / washer | Run a short cycle on each | Clears drain lines and detergent sediment |
| Drains + toilets | Pour RV antifreeze (propylene glycol) | Stops trap water from freezing; non-toxic safe for septic |
Step 5: Final Protection for Unheated Homes
If the house won’t be heated, pour non-toxic propylene glycol-based RV antifreeze into every sink, bathtub, shower, and toilet bowl drain—plus a small amount into each toilet tank. If you plan to keep the house heated, maintain at least 55°F and open cabinet doors under sinks so warm air circulates around pipes. For exposed pipes in attics, basements, and crawl spaces, wrap them with foam pipe insulation or heat tape.
Common mistakes that still cause bursts: closing faucets too soon after draining (trapped water expands and splits the pipe later), skipping the water heater drain entirely, and using too much air pressure.
FAQs
Do I have to drain the water heater every year?
Yes—even in non-freezing seasons, draining removes sediment that builds up at the tank bottom. For winterizing, it is mandatory because standing water in the tank expands when frozen and ruptures the inner lining.
Can I use air compressor pressure lower than 70 psi?
Lower pressure may not push water out of PEX bends or low spots. Anything above 70 psi risks blowing apart copper joints and rubber seals. If 70 psi doesn’t clear the line, the problem is a blocked section or vent, not low pressure.
What happens if I miss draining one toilet?
Water left in the toilet tank or bowl freezes, cracks the porcelain, and leaks onto the floor as soon as the thaw starts. A cracked toilet must be replaced—the damage is not repairable.
References & Sources
- This Old House. “How to Drain Pipes for the Winter.” Covers the full procedure with air compressor pressure limits.