I have far too many memories of freeze damage in "winterized" homes where the winterizing procedure consisted of shutting off the main valve, opening a basement drain in the potable water system, opening all faucets, flushing every toilet, adding automotive antifreeze to traps and toilet tanks/bowls, and turning off the heat.
I’ve also seen damage from homes winterized by blowing compressed air to evacuate water in the hot/cold piping. Then, there were the homes with hydronic heating where no thought was given to winterizing the hydronic system. Split water and hydronic lines in basements often survived, but first- and second-floor water lines and hydronic piping, baseboards and cast-iron radiators often had multiple damage splits, cracks and/or fittings pushed apart. Once the home was sold and the new owners turned the heat and water back on, they discovered they had purchased an indoor sprinkler system! Ceilings, carpet and hardwood flooring damages soon followed, resulting in thousands of dollars for water line repairs and restoration cleanup.
By necessity, we had to cut open ceilings and begin chasing leaks. Fix one, turn on the water, and another leak would show itself. Wet/dry shop-vacs were used to quickly suck up water, and plastic drop cloths were used to collect debris and keep water from doing additional damage to floor surfaces. After removing the plastered ceilings and walls, the reasons for frozen and split or separated water lines became obvious: Low spots, or bellies, that allowed water to be trapped or pooled. It was abundantly clear that relying on gravity alone was not a reliable method for winterizing homes. Pressurized air is one method promoted to forcefully blow water from distribution lines, but that too can leave enough residual moisture in the lines for low spots to collect and freeze. With owners and real estate agents requesting winterization of properties that required a guarantee against freeze damage, I needed to come up with an ironclad solution.
Recreational vehicle antifreeze, which is rated for potable water lines, is nontoxic and bright pink in color, so it's easy for you to see where you've pumped it. RV antifreeze is an ethanol-based product rated to -58° F! We often used a pony-pump to rapidly empty water heaters, and they can generate 10 feet of head, which will raise water 23 feet in elevation. With a self-priming rubber impeller and inexpensive rebuild kits, these little pumps do an awesome job. For higher elevations, we have an industrial model that generates 50 feet of head, but that one also requires a second pair of hands.
The first thing I check is the toilets to ensure they have been flushed. For some reason, folks touring homes for sale forget to flush! At the same time, I’m measuring the baseboard heating because 3/4-inch copper tubing holds slightly more than 2 gallons per 100 feet, and I’ll want to end up with about a 30% hydronic glycol formulated specifically for hydronic systems (do not use automotive glycol).
If there is a whirlpool tub, you can briefly turn on its pump — but adjust the jets downward first! If there's an air pump, I turn it on to forcibly eject any trapped water, and then I'll use the pony pump, with rubber hoses attached, to force the RV antifreeze through one of the jets until I see it coming out of the suction strainer. While the RV antifreeze is draining, I’ll continue on with the survey, but return to the whirlpool tub before turning off the water to rinse away any RV antifreeze in the tub.
Head to the washing machine next, if one is present, and disconnect the hoses. With hoses removed from the washing machine, turn the control to warm and turn on the fill cycle, which will open the solenoid valves and allow water to drain by gravity. Next, pour some of the RV antifreeze into the drum and activate the pump-out cycle to protect the pump and associated lines. This kills two birds with one stone because the pumped out mixture also protects the drainage trap.
If they intend to turn off power to the building, I turn off the curb-valve and cut the water line after the main shutoff valve, if the service line cannot be drained by gravity. If the power is to remain on, then a high quality braided stainless steel self-regulating heat tape is added to protect the service line and valve. There are ball valves with a hasp that you can padlock closed if you are going to guarantee your winterization will be damage-free when the water is turned back on.
I use a 5-gallon clean bucket to mix the RV antifreeze and start with 1/2-gallon of water to 2 1/2 gallons of the RV antifreeze, or you can use 100% RV antifreeze. I’ll start with the cold-water line protection by connecting to the washing machine connection; activate the pump and head upstairs to begin opening faucets until I see the pink color. Close the faucet and head to the next one. Toilets don’t get flushed, but depress the float ball or push down on the ballcock float to allow the RV antifreeze to enter the tank. Then it’s upstairs to do the same with the faucets and toilets. If the fridge has a water dispenser, run that until you see pink, and either run an ice harvest cycle or dismantle the water line and drain the solenoid valve. Don’t forget to open the boiler’s automatic water feeder and inject the RV antifreeze, then close the fast-fill feature.
Back to the washing machine to connect your pump to the hot side. Don’t drain the cold side yet, because we’re going to make good use of the glycol that’s in the water lines. Back upstairs to repeat the same exercise, but don’t forget to activate the dishwasher, and once pink water has appeared, run its pump to provide protection.
Treat the top-floor water closets next by adding automotive antifreeze to the tanks while flushing, which will also protect the siphon jet and rim jets. If you are concerned about the environment, Sierra makes nontoxic antifreeze with propylene glycol instead of ethylene glycol. I make sure my clients know I’m using the environment-friendly antifreeze. Open the hot/cold handles on the top-floor faucets and head to the basement.
Open the waste nut on the main shutoff valve and drain until you see pink, and close the waste nut. Open any outside hydrants until you see pink and close back off. Next comes the water heater's drain and return to the upper floor(s) to open all faucets for gravity drainage, which will treat the water heater (make sure you disabled the fuel source).
Now comes the hydronic system. Using only antifreeze specifically formulated for hydronic systems, mix 1 1/2 gallons of antifreeze to 3 1/2 gallons of water. Isolate the supply/return and pump into a boiler drain on the supply side while allowing water to drain into another 5-gallon bucket from the return side at the base of the boiler. If, for example, there was 200 feet of baseboard and piping for the living areas, that’s going to contain close to 4 1/2 gallons of water. If you don’t see the color of the hydronic glycol, you’ll need to mix some more 30% antifreeze/70% water, and continue until the antifreeze color appears. If you have managed this correctly, you will retain full pressure within the hydronic system. Open the isolation valve and activate the boiler for a few minutes to circulate the glycol mix. If you want to know the exact percentage of glycol in the system, a few drops of the hydronic fluid can be checked using a refractometer.
I winterized dozens of buildings this way and never had any freeze damage. It takes a bit longer and is more expensive, but any realtor who has experienced the horror of the damage brought on from frozen and/or split water lines, or a hydronic system, which will self-drain to the damaged spot and then leak until the auto-fill is shut off after water is reactivated, will see the value and gladly give you the work.
With an iron-clad guarantee that I would pay for any damages and repair the plumbing/heating at no charge if damage from freezing occurred, they had peace of mind and I did, too.