Design & DIY

How much antifreeze is needed to drain waterlines?

How much antifreeze should you use (per toilet, sink, and tub) when draining waterlines in the fall? What is the best type?
—Tony Van Asseldonk, via e-mail

The best type—the only type, for safety reasons—is propylene glycol, a.k.a. RV antifreeze, plumbing antifreeze, or the stuff labelled “non-toxic.” And the amount you put in your toilet depends on its size. Older toilets tend to be larger and will need more, says Dan Flynn, owner of ADF Plumbing in Dorset, Ont.

You want enough to replace the water in the trap; Flynn recommends as much as two litres for a whopper of a throne (or enough to cover 1″ above the weir of the toilet trap; first, empty the tank and remove as much water from the bowl as possible). Don’t worry: Antifreeze is inexpensive stuff, and it comes in big jugs. He also suggests cottagers put half a litre to a full litre in the emptied tank. “This keeps the rubber seals wet all winter long, so they won’t dry out.”

For sinks and tubs, use about a cup. Or don’t use any, if you’re able to get all the water out by draining the traps, says Max Burns, the author of Cottage Life’s Country & Cottage Water Systems. “If it’s a sink that has a drain on the bottom of the trap—and you can get at it—remove the plug to drain the trap, and then 
put the plug back in.” Of course, Flynn warns, with nothing in the traps, stinky sewer gas could back up into the sink and tub. (For a simple fix, stick plugs in the drains over the winter.)

Why bother draining the traps, if propylene glycol is so cheap, safe, plentiful, and stench-stopping? Because it could freeze—and damage your plumbing—if it got cold enough (-35°C to -40°C) in the winter. This probably sounds unlikely, but with our weather, who knows what may happen. As Burns says, “These are weird times we live in.”