Question for the scientists here

[Spock]

Some of our hot Water lines froze during the cold snap but not the cold water lines.

The plumber said that the hot water lines freeze first.

Why?

My uninformed initial thought- it may be that the hot water is less dense and that there is less mass to freeze in a given volume?

[ghostjmf]

Cold water lines are "supposed" to freeze 1st. That's why around here they tell you to leave the cold running a little; keeps the water moving, not freezing. Others say that won't help at all.

What really freezes depends on what line is exposed to the greatest cold, however. If your hot water lines are on an outside-facing wall (on inside-house side of the wall, of course), they might freeze 1st even though having hot water in them is supposed to protect against that.

[gsabc]

Actually, no one really knows, conclusively.

http://www.livescience.com/mysteries/08 ... cubes.html

Me, I'd be checking the location of the hot water pipes relative to the cold water ones. It could be they were closer to the outside walls and therefore subjected to colder temperatures.

[andrewjackson]

This should be interesting.

Remember that there are two issues here. Whether or not hot water freezes faster than cold water and why hot water pipes freeze first. The two are not necessarily the same issue.

My theory on why hot water pipes freeze first is that there is less movement through the hot water pipes so that water cools down uninterrupted. The water in the cold lines is being replaced more often.

We always ran the water at a trickle in really cold temps to prevent freezing of the lines. It worked for us.

[frogman042]

My guess would be that you use the cold water lines more frenquently, thereby causing it to flow and not freeze. I would guess that most of your household appliances (Fridges, washing machines, toilets, etc.) attach to the cold water lines so it gets higher usage.

I think that in a closed system (one where evaporation wouldn't play a factor in cooling it down) that for a given equal volume and assuming the diameter and thickness of the pipes are equal then the hot water would take longer to freeze then the cold water. I'm not sure that there would be that much change in volume between hot and cold water to make the difference in terms of total mass (for example 55 degrees Centegrade (which is probably as hot as most hot water pipes hold) is only about 1.5% less dense than 5 degree C.

Of course I haven't done this specific experment but I would guess usage plays the biggest role.

---Jay

[wintergreen48]

Cold water is tougher; namby pamby hot water just can't handle the weather.

[christie1111]

Cold water is tougher; namby pamby hot water just can't handle the weather.

In my scientific opinion, Wintergreen is right.

[Jeemie]

Cold water is tougher; namby pamby hot water just can't handle the weather.

The simplest explanation is always the best!

[peacock2121]

Cold water is tougher; namby pamby hot water just can't handle the weather.

LOL - I think he is right!

[Bob Juch]

Some of our hot Water lines froze during the cold snap but not the cold water lines.

The plumber said that the hot water lines freeze first.

Why?

My uninformed initial thought- it may be that the hot water is less dense and that there is less mass to freeze in a given volume?

Is it possible that they both froze but only the hot water pipes burst? If so that's because the cold water lines had more air dissolved in the water and therefore had more room to expand.

[DevilKitty100]

Cold water is tougher; namby pamby hot water just can't handle the weather.

Nope......it's the white hot glare of righteousness that keeps the cold water flowing.