Preparing A Hydronic Home Heating System for Winter & Long Vacations

For those who live in the northerly states, it’s becoming more common to do the “snow bird thing” and head south for the winter. If you live in Minnesota, Wisconsin, Upstate New York, or other snowy region, what’s the best way to prepare your water-based (hydronic) home heating system for freezing outside temperatures and an unoccupied house?

If your system is well-designed, winterizing your hydronic system should be a snap, and this article outlines the do’s and don’ts. Most importantly, get in touch with your Xylem RCW dealer, distributor, or installer if you ever have any questions about your system.

Should I drain my system if I go away for a long time?

You shouldn’t have to. Hydronic systems in large buildings do have to be drained from time to time, due to renovations or maintenance issues that arise in long heating loops. But small residential systems seldom if ever need to be drained—for winterizing, to add antifreeze (see below), or for corrosion protection.

Besides, draining a small hydronic system has the potential to cause more problems than it solves. For one, draining means re-exposing your system to oxygen and therefore corrosion. Unless the system is drained completely dry, pockets of rusty water will develop and get to work while you are gone.

Second, a well-designed and tightly engineered “closed” loop will be completely filled with water and need very little “make-up” water during operation—there shouldn’t be any leaks, in other words. A full system means all the oxygen will be accounted for, “locked up” as metallic oxides. No new water means no new oxygen, and no rust.

Third, correctly installed air vents and air separators will have taken almost all the dissolved air out of the pipes. If you have quiet and highly efficient heating, keep it that way by letting your system run through your winter vacation. Remember, if your system is drained, you’ll have to worry about everything that could be damaged by low temperatures while you are trying to enjoy Florida’s balmy weather!

So, I turned my thermostat down, should I check anything else?

Turning your thermostat down so that your system keeps running—just not in “full occupancy” mode—is a great idea. (A thermostat setting of around 55ºF to 60ºF is a good benchmark, although other factors to consider are pets, plants, musical instruments, expensive furniture, and so forth.)

Here is a check list of other steps to take as your prepare your hydronic system for a dormant period:

  • Have the boiler’s burner inspected to ensure it will operate trouble-free while you are away.
    If appropriate, stock up on an adequate amount of fuel.
  • Inspect the relief valve to ensure that it is not clogged and that it will discharge toward a floor drain.
  • Check the pressure gauge to see whether the compression tank maintains an acceptable range as the system temperature goes from minimum to maximum. (If the pressure rises too high, your tank might have a broken diaphragm or be undersized or waterlogged.)
  • Add a low water cut-off protector to your boiler if you don’t already have one. This will shut down the burner in the event of a serious loss of water.
  • Shut the valve between the city water supply and your feed or pressure-reducing valve to minimize water damage in case your system leaks.
  • Lubricate your oil-lubricated circulator pump, if you have one. A wet-rotor circulator (lubricated by system water) does not have to be oiled.

I’ve heard I must add antifreeze to my system in winter—is this true?

Under most circumstances you will not have to add antifreeze to your home heating system. Possible exceptions include systems that have a chance of running out of fuel, remote houses that might lose power for a long period (such as mountain homes where winter storms are common), or systems whose piping is exposed to sub-zero temperatures for extended periods.

Besides, adding antifreeze is a potentially tricky job and should be done by a expert. Knowing exactly how much to add, for instance, requires careful calculation and experience.

It’s important that the right kind of antifreeze be used. Most people know antifreeze as the orange or blue liquid they add to their vehicle’s windshield wiper system. This antifreeze—ethylene glycol—is a poison, and that’s one reason it must never be added to water that is drained into a municipal potable water grid.

Another reason not to use vehicle antifreeze is that it has additives that can adversely affect a hydronic system. The antifreeze that is safe for hydronic systems is propylene glycol, also called non-toxic glycol.

Propylene glycol must be well-mixed before you put it in the system, and therefore it’s best to add it using a mixing tank and pump, something most residential systems don’t have. If you chat with a maintenance technician of a large building, he or she might mention that they use antifreeze in the winter. However, large buildings often have pipes, coils, and components in remote locations that do freeze, and these technicians have the training and equipment to make sure they do this job right!