Photograph of ice on an electric meter and ice on the service entry cable at a building in Rhinebeck NY (C) Daniel FriedmanWinterizing Guide, Heat Turned Off
How to Freeze-Protect Water Supply Piping, Drain Piping, Water Pumps, Tanks, Heaters - Turning HEAT OFF

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Winterizing a building: how to freeze proof a building when heat will be turned off:

This article explains with a step by step guide just how to winterize or freeze proof a building when the building's heating system is going to be turned off completely.

We discuss turning off water supply, draining piping and plumbing fixtures, turning off and if necessary winterizing a heating system, and other steps to avoid freeze damage or water, leaks, and mold damage to buildings that are being left in a "shut down" condition.

The articles at this website will answer most questions about freeze protection for piping and other building plumbing and heating system components: how to winterize a building to avoid frozen pipes, and how to thaw frozen water supply & drain piping, wells, & water tanks.

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How to Winterize a Building If you are Turning the Heat Off - 10 Steps to Freeze Protection

Outdoor plumbing faucet schematic (C) Carson Dunlop Associates

[Click to enlarge any image] Sketch above courtesy of Carson Dunlop Associates.

Is the building heat going to be left "on" or "off" - the answer determines the extent of freeze-proofing needed.

If you have decided to shut down the building's heating system, some steps to protect the building from freeze damage are simple (you don't worry about figuring out the thermostat set-temperature nor about finding "cold spots" where pipes may freeze).

Incidentally, don't make this common mistake: never leave a garden hose attached to your outdoor faucet in winter as water in the hose may add to the risk that the faucet will be freeze damaged. See details about outdoor faucets, hose bibbs, sillcocks

But other critical steps need to be performed if you are going to avoid frozen pipes and future leaks and water damage in a building to be winterized with the heat left off (such as an empty summer cabin, vacation home, or an unoccupied residence.)

  1. Close the main building water supply valve. Check that the valve really closed fully during the process of draining the piping. Be careful: some valves that are seldom used or which are old may not close off completely. You just think you've turned off the water supply, but really your water main valve may still be slowly feeding water back into the supply piping. Details on how to find and use water shutoff valves is
  2. If a water pump and pressure tank are installed, turn off electrical power to the water pump. (Draining the pump and water tank are discussed below.)
  3. Drain the building water supply piping; because most homes other than some vacation cottages are not built with piping intended to be periodically drained, there may be long horizontal pipe runs that will not easily drain out all of their water by gravity, or even some supply pipes that slope "backwards" and refuse to drain.
    1. Use air to remove water: Some plumbers try blowing air through the piping to force out water, or they may install multiple points at which piping can be drained. Below we address some steps to check for frozen, burst piping when turning the water supply back on.
    2. Cut pipes to remove water: Other plumbers will simply cut open any water supply pipe that may not be draining properly, figuring that it's a much smaller repair to later close that cut connection than to fix a building that has been flooded.
    3. Use the building drain: Most buildings include a building drain valve located at or near the lowest point in the building supply piping, but "inside" the building or past the main building water supply shutoff valve.
  4. Drain the building plumbing fixtures, tanks, faucets, such as
    • Winterize hot tubs, spas, whirlpool tubs: remove all water from the fixture if possible: see SPA / HOT TUB DRAIN / WINTERIZING PROCEDURE
    • Winterize toilets, and remove all toilet water from bowls and toilet tanks. Some winterizing companies pour an anti-freeze mix into building toilets and traps. Some anti-freeze chemicals are toxic and should not be discharged into a septic system. See notes below about use of antifreeze in buildings.
    • Winterize water heaters (never turn on electricity to a drained electric water heater, nor turn on power to a gas or oil fired water heater either - it is dangerous and is likely to destroy the heater too)
    • Winterize well water tanks and pumps: need to be completely drained of water - a frozen burst in-building water pump adds an expensive repair later
    • Winterize all building faucets: after water supply has been turned off, open every faucet and leave it open - water left in a faucet can freeze and break it.
    • Open outdoor faucets: be sure also to remove any garden hoses on outside faucets. A garden hose left connected to its outdoor hose hook-up point (the hose bibb) can retain water that freezes and damages the outdoor hose bib (faucet) and can lead to burst piping, leaks, and building damage.
    • Winterize the building supply piping: above we recommended removing all water from the supply pipes, cutting pipes if necessary.

      To be sure that you have not left water in a hidden corner of supply piping somewhere, if you have not done so, see our tips
      at FIND & FIX WATER PIPE FREEZE-UP POINTS discussed under the "heat-on" winterization notes.

      If your incoming municipal water supply piping is not well below the frost line it may be necessary to find or even install a water shutoff valve closer to the connection of your building's water piping to the municipal water main. Private water supply systems are easier to shut down but also need to be drained.

Old water softener needs to be winterized (C) Daniel Friedman

  1. Turn off and drain the water softener or other water treatment equipment.


    This article explains water softener shut-down procedure, explain why we use the water softener bypass valve, and how that can reduce the risk of freeze damaged pipes, leaks, and even indoor mold growth.

    A separate article WATER SOFTENER / TREATMENT TURN-ON provides details on returning a shut-down water softener to operation after it has been shut down.

  2. Winterize all building drains: if you have not already done so, review our tips
    at DRAIN FREEZE PROTECTION which was discussed under the "heat-on" winterization notes. Further steps include removing traps and use of a non-toxic antifreeze in traps or toilets that cannot easily be removed or emptied of all water.
  3. Empty or remove building fixture traps; see our note below about use of antifreeze.

    Use of antifreeze to winterize a building: Be careful: unless the anti-freeze is specifically designed for winterizing a building it could be highly toxic (such as automobile antifreeze).

    We do not recommend using toxic antifreeze to winterize a building since later you're moving that contaminant into the public sewer or into soils (and possibly ground water) around a private septic system. Only inside of closed water systems such as a heating boiler do we recommend use of anti-freeze mix in a building.

Water heater showing drain valve (C) Carson Dunlop Associates

This sketch of a gas-fired water heater and its control valves is provided courtesy of Carson Dunlop Associates.

Warning: do not drain a water heater tank before first turning off its energy source: oil, gas, or electricity.

Heating an empty water tank is very dangerous and is likely to quickly destroy the tank or its heating elements.

  1. Drain the hot water tank and other building tanks: the hot water tank and water pressure tank and pump itself if a private well and tank system are installed.

    Also see WATER SOFTENER / TREATMENT TURN OFF - about turning off water softeners and, if heat is to be turned off, drain the softener and any other water treatment equipment.
  2. Protect well piping from freezing: If your water supply system's piping is not below the frost line your water system should include protection against well or lake water freeze-ups. But sometimes a building's water supply piping that has never frozen before will freeze when no water is run during long periods of freezing weather.
  3. Shut down & drain or freeze-protect the heating system when all other steps to protect the building have been completed:
    • Winterizing forced warm air heating systems: as long as your heating system does not use any water piping (such as a water-to-air system) you can shut off the furnace when leaving a building shut down.
    • Winterizing hot water heating systems: Drain the building heating boiler and heating supply piping, or install an anti-freeze mix in the heating boiler and its supply piping.

      Opening manual air bleed valves can help drain water out of the heating system piping.

      Notify your oil heat supplier if you are turning off heat in the building, and remember to notify them again when it is turned back on.
    • Winterizing steam heating systems: drain the heating boiler and condensate lines and condensate pump if a pump or pumping station are used.
    • Winterizing electric heat or warm air furnaces: can simply be turned off.

    Watch out: for all oil or gas fired heating equipment (furnaces, boilers, water heaters) wWe recommend having the heating equipment cleaned before shutting it down - a step that will avoid corrosion, clogs, and trouble when heat is later turned back on.

Reader Question: How can we test for possible foundation damage if we leave our home with heat off completely?

Sketch of frost heave damage to a slab in an unheated house (C) Carson Dunlop Associates

We built our home 15 years ago. It is a split level with concrete foundation. When we retired we stated to spend our winters in a warmer climate (we live in N. Ontario). Every winter we have left some heat on the lower level of the house keeping the temperature around 4c.

However with the increase in the cost of oil and our dwindling income buying power, we have been thinking of ways we could cut off both the hydro and the oil heater. Is there any way of us testing what effect this might have on the concrete foundations?

The foundation is covered with a layer of ceramic tiles which we later covered over with a laminate flooring. Thank you. - C.W., northern Ontario

Our sketch (left, courtesy of Carson Dunlop Associates) shows what happens when a home is left with heat off in a freezing climate.

Reply: Tests for possible frost damage to foundations? try these local research topics

Sketch of the effects of frost on footings, foundations, slabs (C) Carson Dunlop Associates

I don't know of an actual test that you can perform to predict foundation damage if the heat is left off completely in your building, since testing would require creating the actual freezing conditions and would itself risk building damage. Sketch at left, showing evidence of frost heaving is provided courtesy of Carson Dunlop Associates.

At "A Common Source of Vertical Frost Heave - Un-heated Homes" found in our article
we discuss the problem of foundation damage in un-heated homes.

And at Frost Heave/Expansive Soil Cracks in Slabs we provide more details.

Sketch (left, courtesy of Carson Dunlop Associates) shows upwards as well as horizontal frost pressure on a building and it indicates where cracks and dislocation commonly appear.

Here are some things you can check:

Frost push damage to a foundation (C) Daniel Friedman

Watch out: other factors can still cause slab or foundation damage due to frost.

Other Steps to Reduce the Cost of Heating Left On to Avoid Frost Damage

An alternative to turning heat off in the building entirely is to continue your practice of leaving heat on at a low setting (4 C or about 40 F) but take measures to protect the building from damage (possibly allowing a slightly lower heat setting) and to reduce heating cost by finding and fixing drafts, air leaks, or by improving building insulation.

Building Freeze Protection Articles


Continue reading at ANTIFREEZE for BOILERS or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.


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