You've just handed back the keys after a lovely week on the canals, or perhaps you're the last charter of the season. Either way, your hire firm may ask you to help winterise the boat before you leave. It might feel like a chore when all you want is a cup of tea, but a proper winterisation is the difference between a boat that starts first time in spring and one that needs thousands of pounds of repairs. The good news is that it's mostly common sense, and the hire firm will give you a checklist. Follow it carefully, and you'll be doing your bit to protect the boat through the frosts.

Why a Proper Winterisation Matters

Water expands when it freezes, and that expansion is powerful enough to split rigid plastic pipes, crack metal fittings and even damage engine blocks. A single hard frost can turn a small amount of trapped water into a very expensive problem. Pumps, water heaters, toilets and central heating systems are all vulnerable. The hire firm's checklist exists because they know exactly where the weak points are on that particular boat – every narrowboat is a little different. A few hours of careful work now prevents burst pipes, cracked seals and mouldy interiors later. It also means the boat is ready for the next hirer, or for the owner's own winter cruising.

Start With the Hire Firm's Checklist

Don't improvise. Read the checklist twice before you touch anything. If it says leave a valve open, leave it open. If it says don't drain the central heating, don't drain it. Some systems are sealed and need professional attention; others are simple gravity-fed setups you can drain yourself. Ask a member of staff to walk you through anything you're unsure about. They would much rather answer a question than fix a frozen pipe in January. Sign the checklist when you're done, and note any issues you spotted. That paperwork protects everyone.

Draining the Fresh Water System

This is the most important job. Start by turning off the water pump at the isolator switch, then open every tap – hot and cold – including the shower mixer and any outside tap. That lets air into the system so water can escape. Next, drain the fresh water tank using its drain cock, or siphon it out if there's no drain. Empty the water heater by removing its drain plug or opening the valve at the base. Flush the toilet according to its type: a cassette toilet needs its tank emptied, while a pump-out or sea toilet may need manual draining. Run the pump for a few seconds to clear any remaining water from the lines, then leave all taps open. Any residual water then has room to expand without cracking the pipes.

• Turn off the pump at the isolator switch before you start.
• Open every tap, including the shower mixer, to let air in.
• Drain the fresh water tank using its drain cock or a siphon.
• Empty the water heater – usually a drain plug or valve at the base.
• Flush the toilet according to its type and drain the waste tank.
• Leave all taps open so any leftover water can expand safely.

Adding Antifreeze – Only Where Advised

Antifreeze is not a universal cure, and putting it in the wrong place can cause serious problems. The hire firm will tell you exactly where it is needed. Typically, that means the engine's closed cooling system, where you should check the concentration with a hydrometer and top up with the correct type – usually ethylene glycol, but follow the engine manual. Some central heating systems also need antifreeze, while others must simply be drained. Waste traps and toilet bowls can benefit from a little propylene glycol antifreeze to stop the water in the trap cracking the plastic. Never add antifreeze to the fresh water tank, and never mix different types of antifreeze. Wear gloves, and dispose of any spills properly.

Ventilation: Leave It Open, Not Sealed

It feels wrong to leave a boat open to the winter air, but sealing it up is the worst thing you can do. Trapped moisture causes condensation, which leads to mould, mildew and rusty fittings. Instead, leave roof vents, mushroom vents and a couple of windows slightly ajar. Prop interior doors open so air can circulate through the cabins. Remove bedding, curtains, cushions and any food. If the boat has shore power, a small dehumidifier or moisture traps will help, but only if the hire firm says it's safe to leave them running. Make sure rain can't blow in through the open vents – most are designed to shed water even when partly open. The goal is gentle airflow, not a gale.

Batteries, Fuel and Final Handover

Batteries hate being left flat. Charge them fully, then isolate them at the master switch, unless the hire firm asks you to leave them on a smart charger. Top up the fuel tank to reduce condensation inside it – a full tank is less likely to rust. Check the engine oil and gearbox levels if the checklist asks. Close seacocks only if instructed. Leave the keys where you're told, and hand over any notes about odd noises or leaks. Finally, walk round the boat with a member of staff if you can. A five-minute chat now saves a lot of finger-pointing later. Then you can head home knowing the boat is safely tucked up until spring.