Why Winterising Matters More Than You Might Think

A narrowboat sits in water that hovers just above freezing for weeks on end, while the air inside drops far lower. That combination of cold air, cold water and condensation is what does the damage. Water left in a pipe expands as it freezes, and the pressure is enough to split copper, brass fittings and plastic alike. Damp that creeps into cushions, bedding and bulkheads over three or four months can turn into black mould that stains woodwork and smells for the rest of the season. The good news is that a solid day or two of preparation in late autumn will save you far more time, money and misery when spring arrives.

Drain the Water System Properly

The fresh water system is the single biggest frost risk on any boat, so start here. Turn off the pump at the isolator and open every tap, both hot and cold, to release the pressure. If you have a calorifier, the hot water tank holds a surprising volume that will sit and freeze if you ignore it.

• Isolate the water pump, then open all taps, including any shower mixer, and let them run dry.
• Drain the calorifier by its drain cock, or by removing the lowest connection if there is no drain fitted.
• Empty the toilet cistern, and pump out or drain the bowl on a pump-out or cassette system.
• Blow compressed air through the pipework if you can, keeping the pressure low, around 1 to 2 bar, to push residual water out of low points.
• Add non-toxic plumbing antifreeze to traps, the shower sump and the toilet bowl, or pour in a little propylene glycol-based product rated for potable systems.
• Leave taps open and the pump switched off so any remaining water has room to expand.

If you intend to use the boat through the winter, a small tube heater or greenhouse heater in the bathroom, plus pipe lagging on all exposed runs, is far kinder than constant draining and refilling.

Protect the Engine and Cooling Circuit

Raw water cooling and skin tanks both hold water that will crack castings if it freezes. Check what your engine actually uses before you assume anything. Many narrowboats run indirect cooling, with a closed freshwater circuit containing antifreeze and a separate raw water side for the canal water.

• Test the strength of the engine antifreeze with a hydrometer, and top up or replace so it protects down to at least minus 25°C.
• Drain the raw water side if your boat has one, including the strainer, pipework and any waterlock or silencer.
• Change the engine oil and filter before lay-up. Old oil carries acids and moisture that corrode bearings over winter.
• Fill the diesel tank to reduce condensation in the void above the fuel, and dose it with a fuel biocide.
• Remove the battery or leave it aboard but keep it charged. A smart charger left on a maintenance cycle is ideal.
• Slacken the alternator belt if the boat is laid up long-term, and grease exposed linkages and the stern gland.

The stern gland deserves a mention of its own. If yours is a traditional packing gland, give it a few turns of grease as part of your winter routine, as the grease helps keep water out and keeps the gland supple.

Deal With Damp, Ventilation and Interiors

A sealed up narrowboat is a damp narrowboat. Air needs to move even when nobody is aboard, because warm moist air from the bilges will find cold steel and condense all over it. The aim is gentle through-ventilation rather than a gale, combined with a moisture absorber to mop up what remains.

• Open mushroom vents and leave a couple of hopper windows cracked, sheltered from the prevailing wind to keep rain out.
• Stand mattresses and cushions on edge so air can circulate, and lift them off the base if possible.
• Place moisture absorbers, the calcium chloride type, in the galley, bathroom and any cabin with upholstery. Check and refill them monthly.
• Wipe down and treat any bare steel or rust patches, then coat with a rust inhibitor or oil.
• Remove food, bedding you won't use, and anything fabric that could hold damp and go mouldy.
• Leave internal doors and cupboards open ajar so air reaches every space.

A dehumidifier on a timer can help enormously, but only if the boat is reasonably sealed and the unit has a permanent drain, otherwise you are just heating the canal.

Exterior, Bilges and Shore Power

Once the inside is sound, look at the outside and the systems that keep the boat safe while you are away.

• Check the bilges are dry, then clean them out. Empty bilges freeze and swell, and any oil or water left there will only cause trouble.
• Fit a bilge pump float and test it, and consider an automatic pump with a high-water alarm if you leave the boat for long periods.
• Clear scuppers, drains and cockpit or stern deck drains so rainwater can escape rather than pooling and freezing.
• Inspect mooring ropes and add a little slack for ice movement, and check fenders are secure.
• Disconnect shore power before draining the water system if you are leaving, and make sure any heater left running is on an RCD-protected supply.
• Secure hatch covers, cratch covers and pram hoods, and check for leaks that could drip onto interior woodwork.

A Short Winter Check-In Pays Off

Even a well-prepared boat appreciates a visit every three or four weeks. Walk the bilges for water, sniff for damp, glance at the moisture absorbers and give the engine a turn over by hand if you can. Top up the fuel biocide, check the battery voltage and look for any new rust or leaks. It takes twenty minutes and turns a spring surprise into a straightforward splash of the kettle and a weekend cruise. Treat your narrowboat kindly through the cold months, and she will be ready to reward you the moment the ice clears.