How to Winterise Your Caravan or Motorhome: The Complete Guide

The Complete Winterising Guide

A practical guide from Bedam Leisure — caravan & motorhome specialists

Winterising a caravan or motorhome comes down to three things: get every drop of water out before the first hard frost, keep the air moving so damp can't settle, and keep the batteries charged. The cold itself does almost no harm. What does the damage is water freezing in a pipe or a heater, and moist air trapped in a van nobody visits until March.

Every spring the same repairs come through: cracked Truma heater vessels, split pumps, weeping taps, black spots on the ceiling board, a leisure battery that will never hold charge again, and a motorhome that won't start. Almost all of it is preventable in an afternoon in October. This guide covers the lot, for tourers and motorhomes alike, in the order we'd actually do it.

What you're protecting against

Three things go wrong over a British winter, and all three are preventable. Frost damage: water left in the plumbing or water heater freezes, expands and splits a pipe, a tap body or the heater vessel. Damp: warm, moist air meeting cold surfaces in a closed-up van turns to condensation, and condensation left for months becomes mould in the soft furnishings. Flat batteries: a lead-acid battery left to discharge sulphates internally and may never hold a proper charge again. Motorhome owners have a fourth list on top, because half the van is a diesel vehicle that doesn't like standing still either.

Everything mentioned here is in our winterising collection, all UK stock, so you can work through the job in one go.

1 The water

Drain down — properly

Opening a drain tap and walking away is not a drain down. Water sits in low spots, in pump bodies, in the shower hose, in filter housings and inside the heater itself. What you want is every part of the system emptied until nothing more comes out.

The sequence is the same whatever you tow or drive, and it's best done on the pitch the van will stand on all winter — a van drained level and then parked nose-down keeps a litre in the back of the tank.

1. Switch off the pump and the water heater at the control panel, and let the heater cool.
2. Empty the fresh-water tank and the waste tank.
3. Open every tap, hot and cold, and set mixers to the middle so both sides drain.
4. Open the heater drain valve (the FrostControl or safety drain valve on a Truma) and the low-level drain taps under the van.
5. Lift the shower hose high, let it run back, then hang it down.
6. Pull the filter cartridge out of its housing — it holds water and the housing will split.
7. Empty and rinse the toilet flush tank and cassette, and leave them to dry.
8. Blow the system through, then leave the taps and drain valves open for the whole winter.

That last step is what a drain-down kit does. It pressurises the system with air and pushes the remaining water out of the places gravity can't reach, in a couple of minutes, without you crawling underneath. The kit you want depends on the water system fitted, not the make of the van.

Not sure which water system you have? Look at the external inlet on the side of the van — Truma Ultraflow housings are square with a hinged flap, Whale inlets are round with a bayonet fitting. Our guide to caravan water systems walks through the differences.

2 Frost protection & heating

Frost valves, and the Alde exception

Vans with a Truma or Alde system usually have an automatic frost protection valve. It's a safety device, not a winterising method: when the temperature at the valve drops to around 3°C it dumps the water out of the heater vessel to stop it splitting. It does nothing for the pipework, the pump or the taps, and it only works if the valve is in a serviceable state. Truma are clear that a fully drained heater doesn't need antifreeze in the fresh-water system — draining is the protection.

These valves do fail, and they fail closed, which is the expensive way round. If yours has been in the van a decade, or it has ever dumped when it shouldn't, replace it now rather than discover it in February.

3 The fridge

Fridge off, open — and the vent covers

Switch the fridge off at the panel, clean it out, dry it, and prop the door open on its travel catch. A fridge closed and damp for five months grows mould on the seal and comes out smelling of it. While you're there, empty the freezer box and leave that open too.

An absorption fridge vents to the outside through two wall grilles. Winter vent covers clip over them to keep wind-driven rain, leaves and freezing air out of the fridge recess while the van stands, and they let the fridge work properly if you're touring in the cold. Match the cover to the grille — Thetford and Dometic aren't interchangeable.

Using the van through winter? Follow the fridge maker's instructions on partial covering when running on gas, and take the covers off once the weather warms up. They restrict airflow deliberately — and a gas appliance still needs to breathe.

4 The damp

Condensation and damp: keep the air moving

Warm air holds moisture; cold air can't. When the warm, damp air inside your van meets a cold surface — a window, a metal frame, the underside of a rooflight, an outside wall — it cools below its dew point and the vapour turns straight back into water. In winter the gap between inside and outside is at its widest, so the condensation is heavier. Two people sleeping overnight put out the best part of a litre of water vapour; add cooking, a shower and wet coats and it builds fast.

A caravan doesn't go damp because it's cold — it goes damp because it's sealed. The instinct to shut everything tight is exactly wrong. Ventilation carries moist air out before it settles, and the fixed vents are also a safety system: they let the products of combustion, including carbon monoxide, escape. Never block or tape them over.

In storage

Leave the roof vents on their trickle setting and the floor vents clear. Open every locker, wardrobe and internal door, stand cushions on their edges and lift the mattress so air gets underneath, and ideally take bedding, towels and removable cushions home to store warm and dry. Wipe the cab glass and windows dry before you shut the door — on a motorhome the windscreen is the biggest cold surface in the van. Then put a passive moisture trap at each end. With nothing to plug in, they keep working in the cold when an electric dehumidifier can't.

If you tour through winter

Hold a steady, moderate background heat from the Truma or Alde rather than blasting it on and off — warm enough to keep surfaces above dew point, with the vents open so the moisture can leave. Put lids on pans, never dry washing inside, open the windows for ten minutes after cooking or showering, and wipe the windows first thing each morning, wringing the cloth out outside. A powered roof vent such as the Fiamma Turbo-Vent Crystal clears steamy air far faster than waiting for it to drift out.

Condensation or a leak? Condensation sits on cold surfaces and wipes away. Soft, dark patches around windows, roof seams or the floor that feel damp and won't dry are water getting in from outside — that's one for a damp check, not a moisture trap.

5 The battery

Look after the leisure battery

A leisure battery hates two things: being left flat, and being left part-charged for months. Alarms, trackers and control panels keep sipping power while the van stands, so "it was fully charged in October" isn't the reassurance it sounds like. Charge it fully before you walk away — after a rest, a healthy 12V lead-acid battery should read 12.7V or more at the terminals.

If your storage has mains, leave a smart charger connected in storage mode and it will hold the battery healthy all winter. No power where it's stored? A solar maintainer does the same job from daylight, or take the battery home, keep it somewhere dry and frost-free on a charger, and check it monthly. One caveat: removing the battery can disable an alarm or tracker your insurer expects to be live, so check your policy first.

Running lithium? Most lithium batteries prefer to be stored part-charged rather than at 100%, and many won't accept charge below 0°C — which makes a solar maintainer pointless in January unless the battery is heated. Read the maker's storage note first. There's more in our guide to leisure battery care and charging, and chargers are in our leisure battery chargers range.

6 Motorhomes

The base vehicle: the half a caravan doesn't have

A motorhome is a diesel van as well as a home, and a van that sits unused for five months develops its own problems — a flat starter battery, flat-spotted tyres, a seized handbrake, mice in the wiring loom. None of that is on a habitation checklist, so here's the motorhome list.

Fill the fuel tank. A part-empty tank has a large air space, that air carries moisture, and moisture condensing on cold tank walls is what feeds diesel bug. If the van takes AdBlue, leave a reasonable level in it rather than running it dry.

Keep both batteries charged. The engine battery has its own parasitic drain from the ECU and immobiliser, and it's usually the one that's dead in March because everyone remembers the leisure battery and forgets the starter. A small fold-up solar panel moved onto the starter battery, or a maintainer on each, sorts it.

Don't idle it on the drive. Ten minutes of idling warms nothing properly and never dries the exhaust out. Either drive it for half an hour so everything comes up to temperature, or leave the engine alone and look after the batteries instead.

Handbrake off, wheels chocked — on level, private ground where the storage site allows it. A cable handbrake left on for five damp months is the classic spring phone call: the shoes bond to the drums and the van won't move.

Make it boring to a mouse. Take every crumb and packet out, and check the engine bay for nesting material. Rodents chewing wiring and heater hoses is the single most expensive thing that happens to stored motorhomes, and it costs nothing to prevent.

Gas off at the cylinder, not just at the panel — or take the bottles home. Many storage sites insist on it, and they're the easiest thing to steal off a stored van.

7 The outside

Cover, tyres and security

A good cover keeps months of grime, leaf-fall, bird mess, tree sap and UV off the bodywork, seals and graphics. The one rule that matters: it has to be breathable. A plastic tarpaulin traps moisture against the van and creates exactly the damp you're trying to avoid. Wash and dry the van first — trapped grit becomes sandpaper when the wind gets up — size the cover on the van's length (a motorhome's overall length includes the bike rack and towbar), and check the straps after the first gale. Our guide to choosing the right cover goes into sizing.

Don't forget the tyres. Set them to the correct pressure (laden pressure for a motorhome), park on hardstanding rather than grass where you can, and roll the van a short distance every few weeks so the same patch isn't loaded all winter.

An unattended van out of sight for months is a target, and your insurer will expect physical security. A visible, insurance-approved wheel clamp is the best single deterrent, a hitchlock adds a second layer on a tourer, and a CaSSOA-rated storage site often trims the premium too. Take the satnav and anything with a screen home.

Common questions

Do I need antifreeze in my caravan water system?

Not in the fresh-water system, as long as it's fully drained — draining is the protection, and Truma say a drained water heater needs no antifreeze. The exception is an Alde or wet central-heating circuit, which stays full of glycol all year and should be checked before winter.

When should I winterise my caravan or motorhome?

Before the first hard frost — in most of the UK that means October. If you're still using the van into the autumn, drain down each time you leave it rather than waiting until the end of the season.

Is a cover worth it, or does it cause damp?

A breathable cover is worth it: it keeps rain off the seals and UV off the sealant and graphics. A non-breathable plastic sheet traps moisture and will cause damp. Fit it on a dry day, over a clean van.

Should I start my motorhome over winter?

Only if you can drive it for twenty to thirty minutes so the engine, gearbox and exhaust get properly hot. A short idle on the drive does more harm than good; if you can't drive it, leave it and keep the batteries charged.

Do I need to take the batteries out?

No, as long as they're being charged where they sit — mains, solar or a maintenance charger. Take them out if the van has no power at all and you can't fit solar, store them charged somewhere cool and dry, and top them up every six to eight weeks.

What do I do in spring?

Close the drain valves, fit a fresh filter, refill, sanitise and flush the water system, charge both batteries before you turn a key, and take the vent covers off. Our spring de-winterising guide works through it step by step, and it's the right moment to book a damp check and habitation service.