Short definition

Winterizing piping is the full procedure for shutting off, draining, and protecting plumbing in a home that will be unoccupied through cold weather. It encompasses the supply lines, water heater, fixture traps, and outdoor irrigation — all drained or filled with non-freezing fluid so freeze-burst risk drops to near zero. Standard practice for vacation homes, snowbird absences, and any extended winter vacancy.

What it is

Winterization is the alternative to keeping the home heated through a long absence. Where a 55 °F minimum thermostat works for a week or two, a multi-month vacancy is usually cheaper and safer to fully drain.

The complete winterization sequence:

  1. Shut off the main water supply at the meter, pressure tank, or building isolation valve
  2. Drain all hot and cold supply lines by opening the lowest fixtures first, then the highest, to break vacuum and let water flow out. A small air compressor at a hose-bib connection helps push residual water through long horizontal runs.
  3. Drain the water heater. Turn off power or gas, let the tank cool, attach a hose to the drain valve at the base, open the TPR valve or a hot tap upstairs to vent, drain to a safe location. Tankless heaters need their own manufacturer-specific procedure.
  4. Pour propylene glycol antifreeze (RV antifreeze, food-grade safe — never ethylene glycol auto antifreeze) into every fixture trap. Sinks, tubs, showers, floor drains, washing machine drain. The antifreeze keeps the trap from cracking and maintains the trap seal against sewer gas.
  5. Drain toilet tanks and pour antifreeze into the bowl and tank.
  6. Drain dishwasher, washing machine, ice maker, water filter housings — each has internal water that can freeze and crack components.
  7. Winterize outdoor irrigation — air-blow-out the sprinkler system; drain the backflow assembly.
  8. Set thermostat per insurance recommendation — fully off if drained; 55 °F if leaving heat as a backup safety layer.
  9. Document the state with photos for spring re-commissioning.

For most WA cabins and second homes, DIY winterization runs $20–$60 in supplies and 4–8 hours of work. Pro service in cabin areas runs $200–$600.

Why it matters to a homeowner

The cost differential between winterizing and heating an empty home through WA winter is the deciding factor for most vacation-home owners.

  • Heating to 55 °F all winter in a Cascade foothills or Methow Valley cabin: $500–$1,500 in propane, oil, or electric resistance, plus continued exposure to power-outage risk
  • DIY winterization in fall plus spring re-commission: $60–$120 in materials, plus a weekend each way
  • Pro winterization plus pro re-commission: $400–$1,000 total

Winterization also removes power-outage risk entirely. A heated home depends on continuous electric or fuel supply through winter; a winterized home has nothing to lose if the power fails for a week. For remote properties where power outages are common, this matters.

The trade-off: a winterized home isn’t usable mid-winter. If you want to drop in for a weekend in February, the home needs partial re-commission first, or you accept showering with antifreeze residue in the trap. For vacation homes with active winter use, 55 °F minimum heat is usually the better answer.

Variants — full vs. partial winterization

  • Full winterization — heat off, everything drained, antifreeze in all traps. Standard for unattended cabins through deep winter.
  • Partial winterization — water heater drained and isolated, outdoor branches drained, but house heat held at 55 °F so interior plumbing stays viable for occasional visits.
  • Outdoor-only winterization — applies to occupied homes; just irrigation, sillcocks, and outdoor branches. Inside plumbing stays in service.

Common failure modes

  • Skipped a fixture. Slow leak at re-pressurization in spring; sometimes flooding before the homeowner notices.
  • Used the wrong antifreeze. Ethylene glycol (auto antifreeze) is toxic — must be flushed completely before re-occupation if it was used in error. Always use propylene glycol (RV antifreeze).
  • Didn’t drain the water heater. Tank itself usually survives, but inlet/outlet pipes burst.
  • Dishwasher, washing machine, or ice maker forgotten. Internal water pumps crack.
  • Outdoor irrigation forgotten. PVB cracks; failed annual backflow test in spring.
  • Septic pump tank above frost depth. Water in the pump tank can freeze and damage the float switch and pump.
  • Heat tape unplugged when set up to be on. If partial winterization relies on heat tape, verify it’s energized before leaving.

Washington note

WA’s winterization market is concentrated in:

  • Cascade foothills — vacation homes in Mt. Baker, North Cascades, Snoqualmie Pass, White Pass, and surrounding small communities
  • Olympic Peninsula — coastal cabins and inland properties
  • Methow Valley and Eastern WA — sustained sub-zero winter conditions make winterization standard practice
  • San Juan and Whidbey islands — milder freeze risk, but summer-only homes commonly fully drain anyway for peace of mind

WA insurance policies typically have vacancy clauses that take effect at 30 or 60 days of unoccupied status — read your specific policy before relying on coverage for a vacant-home freeze burst. Documented winterization (photos, receipts from a pro service, or a homeowner-prepared checklist) is often what determines whether a claim pays.

The WA UPC requires fixtures to maintain trap seals when in service. Non-freezing trap fluid (propylene glycol) is the accepted method for winterized buildings — fixtures aren’t “in service” during winterization, and the antifreeze maintains both the seal and the trap’s freeze resistance.