There is a morning in late October when the towpath crunches underfoot and the canal wears a thin skin of grey. That is your cue. A few unhurried hours spent winter-proofing a narrowboat now will save you a great deal of money, swearing and damp bedding when the real cold arrives in January. None of it is difficult, and most of it can be done over two weekends with a kettle never far away.

Drain the water system properly

Frozen water is the single biggest cause of winter damage on boats, and it always finds the weakest point. Start with the fresh water tank. Pump it as empty as you can through the taps, then open the tank drain cock and let the last of it run into the bilge or a bucket. Open every tap in turn, hot and cold, and let the pump run until it is pushing nothing but air. Do not leave the pump running dry for long stretches — a minute or two at a time is plenty.

Next, deal with the places water sits and hides:

• Drain the calorifier or water heater. Most have a drain valve at the base, and many also need the pressure relief valve opened to let air in behind the water.
• Empty the shower tray trap and the U-bends under the sink and basin. A slug of water left here will split the pipe when it freezes solid.
• Pump out the toilet tank, or empty and rinse the cassette. A sea toilet should be flushed through with antifreeze rather than left wet.
• Pour a small amount of plumber's antifreeze into every trap, and leave the taps sitting in the open position.
• Check the central heating and radiators for glycol concentration if the system holds water rather than using a sealed, pre-mixed circuit.

Service the engine before you lay it up

Change the engine oil and filter now, while the engine is still warm and the old oil carries its contaminants out with it. Acids left sitting in a sump over winter do quiet, expensive damage. Fill the fuel tank to the top — a full tank has far less room for condensation to form — and dose it with a diesel bug treatment, then run the engine for twenty minutes so the treated fuel circulates right through the system.

Change the fuel filters and drain any water from the water separator bowl. Check the gearbox oil level, grease the stern gland if you have one, and give the engine a light wipe over with an oily rag to keep the rust at bay. If the boat is going to sit untouched for months, consider fogging oil into the cylinders through the injector ports or glow plug holes. Blank off the exhaust outlet if you are leaving the boat for a long spell, but leave yourself an obvious note to remove it before you next turn the key.

Check the antifreeze everywhere it matters

Test the engine coolant with a hydrometer and aim for a fifty-fifty mix, which protects down to roughly minus thirty-seven degrees. Even if the strength looks right, antifreeze loses its corrosion inhibitors over time, so a full change every two or three years is sensible. While you are at it, check any separate heating circuit, back boiler or diesel heater for the same protection.

If your boat has a raw-water cooling system, drain the seawater side or flush it through with antifreeze. And do not forget the small things: windscreen washer bottles, deck wash pumps, and any hosepipe left coiled on the pontoon.

Ventilation is what keeps damp at bay

The instinct to seal the boat up tight against the weather is exactly the wrong one. A closed cabin turns every breath, every boiled kettle and every damp coat into condensation, and condensation becomes mould on curtains, cushions and bulkheads. Air has to move.

• Keep mushroom vents clear and open, and never tape over low-level vents. Cross-flow from bow to stern is what you want.
• Lift cushions and the mattress off their boards and stand them on edge so air can reach both sides.
• Leave cupboard and wardrobe doors ajar, and slide the bed drawers out a little.
• Put moisture-absorbing crystals in a few places, particularly near the bed and in the wardrobe, and check them monthly.
• If you cover the boat, leave the ends open so air still flows through.

Batteries, bilges and the outside of the boat

Charge the batteries fully, top up any that need distilled water, clean the terminals and smear them with petroleum jelly. Then isolate them — or better still, take them home to a warm garage and put them on a maintenance charger. A small solar panel will trickle a surprising amount through the darkest months if the boat is left outside.

Pump the bilges dry and check that the automatic bilge pump still works. Clear the gutters and drains on the cratch cover, pram hood and roof, so rainwater cannot pool and freeze. Slacken the mooring lines enough to allow for the canal rising and falling, and check them for chafe where they pass through fairleads. Finally, lock up, leave a spare key with someone you trust, and tell the boatyard or marina roughly when you will be back. Then go home, put your feet up, and dream about spring.