Why the first hard frost always catches us out

A narrowboat holds an astonishing amount of water in places you never think about: the calorifier, the shower trap, the pump body, the raw-water side of the engine, the little loop of pipe behind the sink. Water expands by roughly nine per cent when it freezes, and that is more than enough to split a plastic pump housing or crack a copper elbow. One sharp night at minus four is all it takes. The trick is not to wait for the forecast to turn nasty, but to start working through the boat in late October, when the days are still mild enough to enjoy the job.

What follows is the routine I would use on any boat left afloat over winter, whether you visit weekly or only see her at Christmas.

Engine and cooling system first

Indirectly cooled engines with a closed circuit and a skin tank are the easy ones. Test the antifreeze with a hydrometer and make sure it is still protecting down to around minus twenty-five. If it is weak or discoloured, drain and refill with a proper fifty-fifty mix of ethylene glycol and deionised water. Do not be tempted to top up with neat antifreeze.

Raw-water cooled engines need real attention, because canal water sits inside the block. Drain the block, the exhaust manifold and the heat exchanger, then leave the drain taps open. If you can, pull the impeller out of the raw-water pump and store it in a bag indoors so the vanes do not take a set. Empty the raw-water strainer, and check the stern gland greaser is topped up.

Before the cold arrives, change the engine oil and filter. Old oil carries acids and moisture that sit against bearing surfaces all winter. Fill the diesel tank to the brim to cut condensation, dose it against diesel bug, and change the fuel filters and water separator. A full tank with treated fuel is far kinder than a half-empty one left to breathe.

Fresh water: drain it or keep it warm

You have two sensible choices, and mixing them usually ends in tears. Drain down properly: pump the tank as low as you can, open every tap including the shower and the outside tap, drain the calorifier, remove the domestic water pump and take it home, and blow the pipework through with a compressor at low pressure, no more than a couple of bar. Leave all the taps open so any residual water has somewhere to expand.

Or commit to keeping the boat heated. An oil-filled radiator on a frost stat in the cabin, a tube heater in the engine bay, and a small thermostatically controlled heater in the pump locker will see off all but the worst cold snaps. This is the only realistic option if you live aboard, but it does mean you must never let the shoreline trip or the heating run out of fuel.

The systems everyone forgets

• Shower traps and gulper pumps hold a surprising amount of water. Remove the trap bowl, or dose it with antifreeze.
• Cassette toilets: empty and rinse the cassette, and leave the flush tank drained. Pump-out tanks should be emptied before winter if you can.
• Water filters, washing machines and dishwashers all trap water. Run them through their drain cycle and leave the doors ajar.
• Dry the bilges out completely, then add a splash of antifreeze to any low spots that refuse to drain. Clean the bilge pump strainer while you are down there.
• Spare water containers, deck wash pumps and hosepipes stored in a locker will split too. Bring them home.

Beating condensation inside the cabin

Damp, not ice, is what ruins interiors over winter. A sealed-up boat with a bit of warmth inside becomes a condensation factory, and mould follows within weeks.

Keep the mushroom vents open a crack all winter, even when you are away, and let air move through. Prop the mattress on its edge, stand cushions up, and leave cupboard and locker doors open so air can circulate behind them. A dehumidifier with a humidistat, set to around sixty per cent, is worth its cost, but only if the boat is closed up reasonably well. Moisture-absorbing crystals work in smaller cabins and lockers. Wipe down any window frames and hatch surrounds before you leave, because that is where the first black spots appear.

Batteries, fuel and the weekly walk-round

Cold weather saps batteries. Keep them fully charged, check electrolyte levels on open-cell types, and never leave a bank sitting at half charge for weeks. A decent solar panel with a smart controller will trickle them nicely over winter, and a shoreline charger is even better. Isolate everything you are not using.

If you can, visit every week or two. Run the engine up to full working temperature for twenty minutes or so, check the bilges and the engine bay for leaks, sniff for diesel, and look in on the heater. It is a small habit that turns a spring full of expensive surprises into a straightforward relaunch. Look after her now, and she will be ready to cast off the moment the ice clears.