Cold weather!!!

[mas985]

In Northern California, no one does a winter pool closing. We simply decrease the pump run time significantly, drain/isolate any solar system, and let freeze protection work occasionally. Well folks, this is a weird winter so far. The freeze protection has gone on every night for at least the last two months.

It is almost 9 am and the air temp is still low enough for freeze protection. All of my hose bibs are frozen. Water poured onto the concrete patio freezes on contact. It feels like NY, where I grew up.

I checked the water temp and the Jandy says it is 40 degrees. Is this high enough for the freeze protection to be effective? In a normal winter, the water rarely goes below 50 degrees. The run from my pool to my equipment is somewhat long and I don't know how deep the piping is buried because I didn't build this pool.

The cold weather is not expected to break soon. Should I be adding something to the water to lower freeze temperature? My pool is a salt pool, so that should lower the freezing temperature slightly already.

Maybe I should just relax and let nature take its course....

I had the same problem so I decided to risk it and just turn off the freeze protection. Actually, it is not that much of a risk since it takes a long time, probably more than 9 hours, for water to freeze in a 2" PVC pipe so the temps here have not been below freezing for more than 9 hours at a time. Even 2" of water in the dog dish does not completely freeze (my test monitor).

CORRECTION Just checked Yahoo weather and found out that it was below zero for 9 hours last night so I now know it takes longer than 9 hours for water to freeze (and burst) in a 2" PVC pipe. I have solar panels so some air does get into the system after the panels which probably helps some.

[eljefe281]

Here's a fun question for chem geek...

What does 3500 ppm salt do to the freeze point of water?

[waste]

Jefe, As I recall from an earlier discussion here, having salt in the water does lower the freeze temp, but only negligibly. I realize that you asked for Richard's assesment, complete with the need for some asprin or a strong drink to help the info go down( )

Not fully trusting my memory, I did a search and found this thread http://www.poolforum.com/pf2/showthread.php?t=3355. On page 7 (post #62) MassAttack asks a similar ?, Radish responds (post #68) 'that the difference is negligable' and Poolsean (post #70) says that @ 3000 ppm salt the freeze temp drops from 32 to 30.7 deg (F).

I'm sorry my answer isn't as involved as one that Richard could give, but I'd have to say that @ 3500 ppm the freeze temp will be just under 30.5 deg.

There's the 'quick and dirty' answer, I'll leave it to Richard, or one of the other chemists to give the 'whole story'

[salinda]

Looking in hindsight at the cold winter we have had, I feel a bit of satisfaction and vindication over one thing in particular. This summer, I got a bug over the high (33-35 cents/KW-hr) rates here. We replaced a 2hp whisperflo and a Polaris booster pump with an Ikeric variable speed pump. It is not perfect. I wish that I had the Intelliflow installed instead and I also think that a robotic or even pressure-side with booster would have been more in my comfort zone, but my electric bills for this winter showed that we consistently used 300 KWhr/month LESS this year than last year. Remember the pump ran MANY more hours than last year due to the freeze conditions. Some weeks, it ran almost around the clock. Last year, maybe 2 weeks were like that. That is $100 savings per month. With winter alone, I will make back the high replacement costs I paid in no time.

Hurray!

[chem geek]

Here's a fun question for chem geek...

What does 3500 ppm salt do to the freeze point of water?

Sorry I didn't notice this question to me before now, but the answer is, of course, disappointing. Remember that the freezing point depression for water is 1.86 ºC/m. 3500 mg/l / 58.44 g/mole / 1000 mg/g = 0.060 moles/liter which is essentially 0.060 moles/kg solvent (which is what "m" is...molality).

So 0.060 * 1.86 = 0.11 C = 0.20 F. Yes that's right, the salt in your pool only reduces the freezing point of water by 0.2 degrees Fahrenheit.

Richard