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I have a water hose that I keep hooked up all the time. It's inconvenient to disconnect and drain the hose to protect it from freezing. My plan is to watch the weather forecast and only disconnect if necessary because it will be cold.

How cold does it have to get to freeze the water and damage the hose?

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3 Answers 3

In general, "cold enough to freeze water inside the hose".

Eighth grade physics tells us that water expands when frozen. Consequently having standing water inside a sealed container is not going to be good for the container's health.

The real problem is draining the hose rather than storing it. However, water being a fluid gets into all kinds of cracks, so storing the hose in a heated area is probably useful.

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Generally, residual moisture won't be a problem as long as the hose has no standing water in it. Droplets, when they freeze, will simply expand out into the air in the hose. It's when there's no air in the hose (or some length of it that has standing water) that damage can occur. –  KeithS Dec 12 '11 at 18:13

Can you turn off the water supply to the hose? Or is the tap at the "business" end of the hose?

If it's the former then you can turn off the supply to the hose and leave the tap at the end of the hose open. This means that if there is any water left in the hose it will a) drain away and b) (more importantly) be able to expand safely along the length of the hose if it freezes.

So as long as there aren't any kinks in the hose it should survive the winter.

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This is what I do, though not all winter. See also gardening.stackexchange.com/questions/2704/… –  Kate Gregory Dec 8 '11 at 12:14

If the weatherman predicts a freeze of any kind (as in air temperature lower than 32*F or 0*C, either disconnect and drain or "drip" the hose.

When water freezes, it expands. This is what causes the damage. Certain types of hose are more forgiving than others; your "garden-variety" (NPI) water hose, which is simply unreinforced vinyl, will usually stretch to the degree necessary to avoid freezing. However, if the water is normally under pressure, the hose will already be stretched a bit, then it will stretch more when the water freezes, and then when the water thaws it will remain stretched that much more. Eventually, given enough freeze/thaw cycles, the hose will fail.

Reinforced hoses are usually some rubber composite with nylon or metal mesh inside to provide some tensile strength. They're designed not to stretch as much, and so will actually fail faster in a freeze (when water freezes, it WILL expand; if "frost heaves" can destroy a house through water collecting in cracks or against walls designed to withstand tens of thousands of pounds of load, your average garden hose stands no chance).

If the hose normally has to remain connected, and disconnecting it is a pain, consider a combination of insulation and "dripping". Insulation will help protect the water inside the hose from the cold temperatures outside, so it will take longer to freeze; a quick "arctic blast" will be less likely to cause a problem.

Dripping helps in three ways:

  • First, moving water is much less likely to freeze solid; it will instead form smaller crystals that will be swept along in the stream of liquid water (this basic principle is how slushie machines work; you keep the liquid moving, and it will remain fluid even at freezing temperatures).

  • Moving water also causes pressure differentials in a pressurized water line; as the temperature drops, ice will start to form on the pipe walls and grow inward. As this happens, the flow of water becomes restricted. With the dripping end of the line relieving pressure on that end of the line, backpressure will build, forcing the water through the remaining gap at higher pressures, keeping the line open even if it's restricted.

  • Lastly, keeping the water moving, no matter how slowly, keeps water coming in from "upstream" to add heat to the places that are susceptible to freezing. Many people don't know this, but in addition to the energy needed to heat water (or that needs to be removed to cool it) by one degree, additional energy needs to be added or removed in order for the water to change state. To cool water from 2*C to 1*C requires removing 4.18 J/g of energy from the water; however, to go from 1*C to 0*C and actually freeze the water requires 334 J/g, almost 80 times more energy removed. So, water will remain liquid at ambient temperatures below 0*C until the system manages to remove enough mean energy from the liquid water to freeze it. As long you pump even a tiny bit back into the system by dripping the faucet to introduce warmer water, you can keep water liquid indefinitely until the temperature gets so cold that heat is lost faster than it is being introduced (at 0*F, about -18*C, unprotected outside lines are at real danger of freezing no matter what).

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