Pump operation during freezing conditions

[Kidney]

It's been quite a while since I posted. I've been enjoying summer and my recently resurfaced pool ;-) I've also followed BBB for water maintenance and what a delight it is: no algae whatsoever, and currently maybe a cup of 8.25% bleach a day or every two days keeps my Chlorine level in check! Only small pb is pH rises (I have no borates and am considering adding them) but baking soda + muriatic once a week and water is all balanced: fantastic!

I am coming today to seek advice re winter operation. I have a spa on the same piping circuit as the pool (it overflows into pool). I will keep using the spa all winter long so my VSP is running at 600 rpm constantly when air temp is near freezing. Water is yet to deep below 45F at the pump or the heater (that both show me the water temp when asked). Since there are pipes above ground at say 2 to 3 feet in the air, should I increase that rpm to a higher setting to avoid water freezing inside them or is the simple continuous but slow flow of water sufficient to prevent freezing inside them even at this low rpm? If 600rpm is not enough, is there a rule of thumb for how fast it should be?

Thank you!!!

[mas985]

Even the slowest speed on a VS is not all that slow in terms of flow rate (15-20 GPM) and should be more than sufficient to prevent freezing. However, you should have contingency plan in case there is a power outage or the temperature sensor fails. One cost effective method to increase the amount of time it takes to freeze the pipes is to simply cover the equipment with a tarp. This reduces heat loss from the plumbing and can increase the time to freeze by 3x. Adding a light bulb will prevent freezing of the pad equipment all together even without the pump running.

However, if you are only running the pump without some of these extra protection, then make sure water flows through every part of the plumbing. More complex setups often neglect portions of the plumbing when automated freeze protection is used.

[Kidney]

Thank you Mark for your very good and quick answer! So in essence, as long as the water moves, even at slow speed, it will not freeze (and yes I have it moving through all pipes/parts of the system). It seems as temperature has been going down in my part of Texas that even though air temp was below freezing, pool temp only decreased by 1F a day or so hence remained quite warm. I am not sure at what air temp, pool water would start freezing but it would surely freeze quicker in the pipes if left immobile so your suggestion of using a tarp is great, not to mention a tarp would protects against UVs that have been degrading plastics fairly quickly already. The light bulb would have to be underneath the tarp to generate enough heat: any idea of the wattage needed?

I have a separate question re bleach in case you know: I wonder at what air temp it would freeze. I have it in the garage currently and add it manually but am thinking about adding a Stenner pump for automatic additions. And I also wonder if muriatic acid freezes. If either freezes and expands, there could be some serious damage ;-(

Thank you!

[mas985]

I won't go as far to say that it would never freeze because if it gets cold enough, it will still freeze but that would require much lower temperatures (e.g. < 0F).

A 60 watt (incandescent) should provide more than enough heat.

If interested in the physics of freezing, you can read this thread (http://www.troublefreepool.com/threads/86914-The-Physics-of-Freezing-and-Freeze-Protection).

As for the other questions:

http://www.poolforum.com/pf2/showthread.php/8175-Clorox-and-Freezing

http://www.poolforum.com/pf2/showthread.php/6325-Muriatic-acid-storage