The Boat Floats

Guide

Winterising Your Narrowboat

If your boat sits unused for weeks of cold weather, a few hours' winterising in autumn protects it from frost damage that can cost thousands. This guide covers

4 min read · Updated 2025-11-06

Winterising Your Narrowboat

If your boat sits unused for weeks of cold weather, a few hours' winterising in autumn protects it from frost damage that can cost thousands. This guide covers the essential steps for a leisure boat being left over winter, plus the reduced version for liveaboards staying on board.

When to winterise

Winterise before the first hard frost - typically late October to mid-November in the UK, earlier if your boat is somewhere exposed. Don't wait for a frost forecast; once water lines have frozen and split, the damage is done.

The big risks

  • Burst water pipes. Frozen water expands and splits copper and plastic pipe.
  • Cracked calorifier. A frozen hot-water cylinder can split.
  • Broken pump. Water in the pump body freezes and shatters the housing.
  • Cracked engine block. Coolant freezing and expanding.
  • Frozen toilet system. Macerator pumps especially.
  • Battery damage. Discharged batteries freeze and crack.

Step-by-step (leisure boat)

1. Drain the water system

  • Turn off the water pump
  • Open all taps, hot and cold
  • Open any drain cocks on the boiler/calorifier
  • Drain the fresh water tank (or leave half full to avoid floating freeze)
  • Open the shower mixer to drain
  • Run the pump dry briefly to clear it
  • Some boats have a low-point drain on the pipework

For belt and braces: blow through with compressed air or pour antifreeze (RV/marine type, not engine type) through the system.

2. Drain or antifreeze the toilet

For pump-out toilets, flush all water through and pour antifreeze into the bowl (it sits in the macerator). For cassette toilets, empty the cassette and rinse.

3. Engine

  • Top up coolant; check antifreeze concentration with a tester (need -20°C minimum)
  • Top up fuel tank to reduce condensation
  • Add a fuel stabiliser
  • Engine oil and filter change before storage is good practice
  • Disconnect or remove batteries (or fit a smart trickle charger if shore power is available)

4. Diesel heating

Run the Webasto / Eberspacher for 30 minutes to clear lines. Some owners drain the day tank if the boat will be unused for months.

5. Stove

  • Clean out the firebox and ash pan
  • Brush out the flue
  • Cover the chimney top to keep rain out
  • Leave the stove door slightly ajar for airflow

6. Soft furnishings

  • Remove cushions and bedding to home if possible (damp ruins them)
  • Otherwise stand cushions on edge with airflow round them
  • Open cupboard doors and drawers slightly

7. Bilge

  • Pump out the bilge dry
  • A small amount of antifreeze in the lowest point catches drips

8. External

  • Check mooring lines (rotate to fresh ones if old)
  • Add extra fenders against winter wind
  • Check the weed hatch seal
  • Cover the back deck if you have a cover
  • Set the bilge pump to automatic if it isn't already

For liveaboards

If you're staying on board:

  • Keep the heating on continuously, even when out for the day
  • Insulate exposed pipes (foam tubing)
  • Drip a tap overnight if extreme cold is forecast
  • Top up coal/wood/diesel before snow
  • Stock food for a snowed-in week
  • Salt the towpath edge near your mooring (if permitted)

Snow and ice on the boat

  • Sweep snow off the cabin top regularly (it gets heavy)
  • Don't try to break ice round the boat with anything that could damage hull or paint
  • If the canal freezes, don't cruise; ice damages hull paint and propellers

Mooring in winter

Some marinas offer winter-only moorings at lower rates. CRT online moorings are valid year-round but check towpath access if snow is heavy. For continuous cruisers, plan winter moorings somewhere accessible to shops, water and disposal points.

What to check on first spring trip

  • Bilge dry?
  • Engine oil level?
  • Coolant level?
  • Stern gland (gentle weep)?
  • Battery voltages?
  • All taps run?
  • Toilet flushes?
  • Heater fires?
  • Gas works?

A spring "wake-up" service - oil change, fuel filter, full systems test - is good practice.

A winterising checklist

  • Water system drained or antifreezed
  • Pump cleared
  • Calorifier drained
  • Engine coolant antifreeze tested
  • Fuel tank topped up with stabiliser
  • Toilet drained and protected
  • Stove and flue cleaned
  • Bedding removed or aired
  • Bilge pumped, antifreeze added at low point
  • Mooring lines and fenders refreshed
  • Bilge pump on automatic
  • Insurance notified if boat is laid up

Conclusion

A few hours of winterising in autumn saves potentially thousands of pounds in spring repairs. The single biggest preventable damage is from frozen water pipes; drain the water system thoroughly and you've covered the worst risk. Add the engine and battery checks and your boat will wait quietly until you come back.