Plumbing antifreeze: where it goes (traps, toilets, drains)

The cottage plumbing is drained, the taps are open, and one question is left: where does the antifreeze go? A forgotten trap means a cracked drain or a split toilet come spring.

Antifreeze doesn’t replace draining. It protects the places that have to hold liquid: traps, the bottom of the toilets and the drains. Here’s which ones, with what product, and where it should never go.

What to do, step by step

1. Pick the right product

Buy antifreeze made for plumbing or for RVs, labelled as such. These products are generally propylene-glycol based.

Never use automotive antifreeze. It’s ethylene-glycol based, and Health Canada notes that swallowing ethylene glycol causes serious toxic effects. It has no business in a drain that runs to a septic tank or near a well.

Read the label: some products are sold ready to use and aren’t meant to be diluted. Store the jugs out of reach of kids and pets.

2. Sink and vanity traps

The trap is the U-shaped section under the sink. It stays full of water to keep sewer gas from coming up, and that water is exactly what freezes. Once the plumbing is drained, slowly pour antifreeze into every sink and vanity, enough to replace the water in the trap. No more.

3. Showers and tubs

Same idea: the shower and tub drains each have a trap under the floor. Pour the antifreeze straight into the drain.

4. Toilets

Flush with the main shut-off closed, then sponge out the water left in the bottom of the tank and the bowl. Then pour antifreeze into the bowl so the toilet’s trap stays protected. For the tank, ask your plumber whether a little in the bottom makes sense for your model.

5. Floor drains

The drain in the basement, laundry room or furnace room has a trap too. If it dries out or freezes, sewer smells come up or the drain can crack. Pour antifreeze in slowly.

6. The washer standpipe

The vertical pipe your washer drains into has a trap at the bottom. Pour antifreeze into it. For the washer itself, and the dishwasher, follow the manufacturer’s winterizing guide: some call for antifreeze, some don’t.

7. Write down what you did

A simple list posted by the main shut-off: which traps, which toilets, which product, what date. It helps whoever checks on the place over winter, and it helps at the spring opening.

Where it never goes without a plumber

• Into the drinking-water lines. Some plumbers use it to protect a system that’s hard to drain, then flush it thoroughly in spring. That’s their job, not a step to improvise.
• Into hot-water heating. Hydronic baseboards and radiant floors use products and mixes specific to the system. Only the technician who services it should touch it.
• Into the well or the pressure tank.
• Into the sump pit. It isn’t a trap: water that collects there gets pumped outside.
• Into a sewage ejector pit. Ask your plumber.

Why it matters at a Townships cottage

Traps are often in the cold spots. A cottage added onto in stages in Sutton, Dunham or Potton sometimes has a bathroom over a crawl space, or a floor drain against a foundation wall. Those are the first places to freeze in an unheated house.

The septic tank gets everything. In spring, the antifreeze in the traps and toilets ends up in the tank. Hence two simple rules: a product made for plumbing, and only the amount you need. If you’re unsure about your system, check with your municipality or the company that pumps it.

Winter swings between freeze and thaw. A trap that freezes once doesn’t always crack. But cycle after cycle, the risk comes back all winter.

What you can do, and what belongs to a plumber

What an owner can do:

• Buy the right product and read the label.
• Pour antifreeze into sink, shower, tub, floor-drain and washer-standpipe traps.
• Empty the toilets and protect the bowls.
• Keep a list of what was done.
• In spring, run water down every drain once the water is back on.

What belongs to an RBQ-licensed contractor:

• Fully draining the plumbing before the antifreeze goes in.
• Any use of antifreeze in drinking-water lines, and flushing it out.
• Hot-water heating, the well, the ejector pit.
• Turning the water back on in spring, if a plumber drained the house.

Check a contractor’s licence in the Régie du bâtiment du Québec registry. For the draining itself, see draining your cottage plumbing for winter, step by step.

In an empty house, how long before anyone notices?

A forgotten trap is invisible. A toilet that cracks in a closed house doesn’t leak much: with no water under pressure, the damage often stays limited, but it gets found in spring, along with the sewer smell and a repair to make before you can use the cottage.

The bigger risk is elsewhere: if someone turns the water back on by mistake, or a valve lets a trickle through, a drained house fills up again and nobody knows. How often someone stops by sets the maximum length of any damage.

What we look at on a visit

Every visit, we check that the main shut-off is still in the agreed position, open the cabinets under the sinks and look behind the washer, look at every toilet (bowl level, ice, antifreeze still there), and run a flashlight over the basement floor and lower walls around the drains. Every finding is photographed and time-stamped in the report.

If something’s off, we call you the same day, with photos. If needed, we meet an RBQ-licensed plumber on site and document the work.