Why Winter Bites Harder On The Cut

Come November, the canal network turns quiet and often beautiful — and also quietly treacherous. Here's the odd truth about cold weather and steel boats: a boat sitting in water is usually better off than one sealed up and forgotten. The cut below the hull hovers around 4°C even in a hard frost, which keeps things surprisingly stable down there. The damage happens above the waterline, in pipework, pumps, engines and batteries left to fend for themselves.

Frost is patient. It finds the water hiding in a pump housing, the thin layer sitting in the bottom of a calorifier, the dribble in a shower gulper. It expands, and something splits. An afternoon's work now is worth a fortnight of repairs in February, and the jobs below are all well within reach of a reasonably handy owner.

Drain The Fresh Water System

This is the single most important job, and it's the one most often half-done. Empty the main water tank, then run the pump with every tap open until nothing but air comes through. That includes the shower mixer, the basin, the galley tap and any outside tap you've fitted. Once the pump is running dry, switch it off and open the taps again so any trapped water has somewhere to go.

• Drain the calorifier using the drain cock at its lowest point. If there's no drain cock, this is the winter you fit one.
• Empty the water filter housing and remove the cartridge — a frozen cartridge bowl cracks easily.
• Clear the pump and pipework by disconnecting the pump inlet and running it briefly, or blowing through with low-pressure air if you have it.
• Pour non-toxic antifreeze down every sink, basin and the shower trap. Use the pink plumbing-grade stuff, never the blue engine coolant, which is toxic and will damage seals.
• Toilets need attention too. Drain the flush tank on a cassette model, and on a pump-out system flush non-toxic antifreeze through the bowl and pipework.

If you live aboard, don't drain anything — instead keep the boat warm and keep the water moving. A frost stat or a small oil-filled radiator placed near the water pump and calorifier will keep the critical parts above freezing overnight.

Engine, Fuel And Batteries

Your engine has two very different cooling arrangements, and which one you have changes the work required. If your engine is raw-water cooled, it draws canal water through the block and there's no antifreeze to protect it — you must drain the block, heat exchanger and exhaust manifold properly, following the engine manual, or you'll be looking at a cracked block in spring.

If your engine is indirectly cooled, the closed circuit should already contain a 50/50 mix of antifreeze and water, which protects down to roughly -35°C. Check its strength with a hydrometer or refractometer, and if it's weak or the coolant is brown and tired, change it now rather than in March. Top up the raw-water side with antifreeze only if the manual calls for it.

• Fill the diesel tank to the brim to reduce condensation and the risk of diesel bug.
• Change the fuel filters and drain any water from the sedimenter.
• Service the engine as normal — clean oil is far kinder on a cold start.
• Batteries lose capacity fast in the cold. Keep them charged, ideally above 80%, top up non-sealed cells with distilled water, and check terminals for corrosion.

Heating, Ventilation And Damp

A sealed-up boat grows mould faster than an open one freezes. The trick is to keep a little air moving while keeping the warmth in. Leave the mushroom vents clear and never stuff insulation into them — condensation needs somewhere to escape.

If you're aboard through the winter, keep the fire or stove in overnight rather than letting the boat swing between 20°C and zero. If you're away, a thermostatically controlled oil-filled radiator on a low setting, plus a dehumidifier with a permanent drain hose into the sink, is a sensible combination. Lift cushions and mattress edges so air can circulate, and leave wardrobe doors and cupboard doors ajar.

Insulate the obvious weak points: window covers, a cratch board or pram cover, and any exposed pipe runs in the engine bay or under the stern deck. A lagging jacket on the calorifier and pipe insulation on the water lines cost very little and pay for themselves many times over.

Outside, Moorings And Gas

Walk the outside of the boat with a critical eye. Canal water levels rise and fall in winter, especially after heavy rain on the rivers, so check your mooring lines have slack and that they aren't chafing through on a fairlead. Fit chafing sleeves, check your fenders are secure, and make sure the weed hatch is properly sealed.

• Clear the gas locker drain so any water or escaping gas can escape freely.
• Check the bilge is dry and the bilge pump works — a blocked pump and a leaking window is a bad combination.
• If the chimney isn't in use, remove it and fit the blanking plate, or water will run straight into the stove.
• Give the hull a look over at the waterline for damage before ice forms.

If You're Leaving Her Unattended

Short absences need less work than a two-month abandonment. If you're away for a few weeks, leave the heating on a frost setting, keep the batteries on a smart charger or solar panel, and ask a friendly neighbour or the mooring warden to look in every week or so. If you're away for the season, drain the water system fully, remove all soft furnishings and bedding, prop up cushions, and leave the boat ventilated and locked with a note of emergency contacts somewhere sensible.

A boat that's been winterised well rewards you on the first mild day of spring: turn the water back on, check for leaks, charge the batteries, and she's ready to go. Take an afternoon now, and the cold months will pass without costing you a penny more than they need to.