Winters in the Charleston, SC Lowcountry are not typically described as harsh. We don’t usually get many nights of temperatures falling below the 32 degree threshold. But when temperatures do fall below freezing, the most common items that we see suffer freeze damage are outdoor located backflow prevention assemblies.
Backflow prevention assemblies are required if you have an irrigation system at your home or business and they are not cheap. Many businesses are required to have backflow prevention assemblies for numerous reasons. So how do you protect them from freezing on one of our rare freezing nights? Let’s discuss in more detail.
Most backflow prevention assemblies are made of brass and are full of water. Most residential backflow prevention assemblies are installed on irrigation lines and located outdoors, which leaves them exposed to the weather.
Every winter plumbers preach, on cold nights, to drip/stream your hot and cold water to protect your pipes from freezing. That’s a great habit to practice, and it will protect a business’s domestic backflow prevention assembly but streaming hot/cold water indoors will not protect your irrigation backflow prevention assembly. Once the water in your assembly begins to freeze, it expands as it turns to ice and can crack the copper piping and brass assembly (or any other piping and material used).
Bottom line, stagnant water exposed to freezing temperatures can and will freeze if the temperatures stay cold enough for a long enough period.
Please bear in mind, I’m not a scientist, so this is just basic stuff I’ve learned as a plumber over the past 25 years. So as a plumber, I only know of 2 ways to prevent potable water from freezing: heat and motion.
First, if the freezing point of water is 32 degrees and you keep the water’s temperature above 32 degrees, using a heat source, it will not freeze. Many commercial backflow prevention assemblies are located inside of a climate controlled building, so freezing temperatures and theives don’t affect them. (***A quick note – insulation bags do not produce heat).
With over 25 years of backflow experience, we’ve seen numerous methods employed to try to prevent freeze damage to backflow prevention devices. Blankets taped around assemblies, boxes filled with insulation, newspapers and magazines wrapped around the assemblies. None of these methods worked.
We’ve also seen electric heat strips used, which actually worked, but we never recommend wrapping electrical wire around copper piping to avoid a potential electrical hazard. Nor do we recommend using electric heating pads, but we’ve seen it.
We’ve also seen electric space heaters and kerosene heaters used to try to protect backflow prevention assemblies from freezing. Again, because of the electrical hazard and fire hazard, we do not recommend these methods.
Most often we see insulation bags covering backflow prevention assemblies. But after 25 years, I can tell you that insulation bags will not prevent your backflow prevention assembly from freezing, especially if we fall below freezing for many hours or days. Using pipe insulation won’t prevent the piping to your assembly from freezing either.
Second, moving water tends not to freeze, especially in our environment where freezing temps don’t typically last for 24 hour periods for many days and weeks. So if the water is constantly moving through your backflow prevention assembly, it will not freeze.
So how do you keep water moving through a backflow prevention assembly?
Technically, you could go outside drain your irrigation system and turn on the number 2 test port (on a PVB) or the number 4 test port (on a DCVA or RP) to drip your backflow prevention assembly. But how many of us will actually do that every time it’s going to freeze?
I prefer something easier than having to mess with the test ports every time it freezes, such as a freeze protection valve.
In my 25 years of backflow experience, I’ve learned that the easiest way to prevent freeze damage is to install a freeze protection valve. I personally have one and I’ve never had any freeze damage to my backflow prevention assembly.
I don’t use my irrigation system in the winter, so I turn off my number 2 shut off valve, drain the irrigation system, and my FPV does the rest.
Freeze protection valves use the same method as dripping your faucet. When the water temperature gets close to freezing the valve will start to drip. The colder the temperature gets, the more water the valve will discharge. The freeze protection valve protects your backflow prevention assembly by ensuring the water inside is constantly moving, thus preventing the water inside from freezing, turning to ice and damaging your assembly.
Given how expensive backflow prevention assemblies can be, I highly recommend using a FPV to protect it.
Call us today for more information about installing a freeze protection valve to protect your backflow prevention assembly. And if you need help freeze damage to your backflow prevention assembly, we can help with that to.
Thanks for reading and we hope we’ve given you some good information to consider.
It doesn’t freeze very often in the South Carolina Lowcountry, but when it does, your plumbing can be seriously impacted. So when you see freeze warnings for our area, take the time to protect your plumbing and hopefully you’ll save yourself from an expensive plumbing repair bill.
A few tips to protect your plumbing from some scary Halloween dangers.
Should you use liquid clog removers or liquid drain cleaners to try to remove a plumbing clog in your home?
Swell Guy Plumbing Co is a local and licensed plumber serving the Charleston, SC Lowcountry area.
We bring over 25 years of Lowcountry plumbing experience to your home or office.
Steven Dyson, owner, is a lifelong Lowcountry resident, and a licensed plumber in South Carolina (M115194).
Serving: Goose Creek, Hanahan, Ladson, Moncks Corner, North Charleston, Summerville, and West Ashley, SC.
Swell Guy Plumbing Co is ready to help, so feel free to call us because you’ll always speak to a knowledgeable Lowcountry plumber.
© 2026 Swell Guy Plumbing Co.. All Rights Reserved. SC# M115194
Freezing temperatures are expected in our area.
Please take steps to protect your plumbing and avoid costly plumbing repairs.
