For second home winter leaks, both a full drain-down and heating left on frost-protect can work, but each fails differently. A drain-down must reach every low point, including outside taps, or trapped water still freezes. Heating-on depends on power, boiler and thermostat staying reliable while you're away. Whichever you choose, arrange a periodic check, since most winter leaks are found late simply because nobody was looking.
Cornwall and Devon have a high concentration of second homes and holiday cottages left empty for weeks at a time over winter, and every owner faces the same decision each autumn: drain the water system down completely, or leave the heating on low to keep everything above freezing. Both are legitimate strategies, and both go wrong in different ways. This guide sets out the trade-off plainly, plus the checks that catch second home winter leaks early, whichever route you take.
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The choice: drain down or heat on
Neither option removes risk entirely, and the right one often depends on how the property is built, how reliable the power supply is, and how often anyone can check on it. A drain-down takes the water out of the equation, nothing left to freeze means nothing left to burst, but it only works if every part of the system is actually emptied. Heating left on a frost-protect setting keeps the whole system above freezing without needing to empty anything, but it depends on the boiler firing, the power staying on, and the thermostat being set correctly, all unattended.
Owners who split time between a main residence and a Cornwall or Devon second home tend to lean one way based on past experience, often their own or a neighbour's. Both are sound approaches when done properly. The failures we're called out for tend to come from a version of either done partway.
Draining down properly
A drain-down sounds simple, turn off the supply, open the taps, let it empty, but the detail is where it goes wrong. Water finds the lowest point in any system, and if that low point isn't drained too, it sits there through the coldest nights of the year.
- Turn off the water at the stop tap (usually under the kitchen sink, or at the boundary if there's no internal stop tap).
- Open every tap in the house, starting upstairs and working down, so air can get in as the water drains out.
- Flush toilets to empty the cistern, and consider adding a suitable antifreeze product to the remaining bowl water if the property will be empty for an extended period.
- Drain the hot water cylinder, if fitted, using its dedicated drain valve, and check the loft tank (if there is one) has fully emptied.
- Isolate and drain any outside taps separately, since these are often on their own short run and get missed in a whole-house drain-down.
- Leave the boiler drained per the manufacturer's instructions, or set to frost-protect only if you intend to leave power connected and are not fully draining the heating circuit.
Leaving the heating on
The alternative is to leave the heating running on a low, frost-protect setting rather than draining anything. Most modern boilers and room thermostats include a frost-protection mode, often somewhere in the 5 to 12 degree range, that keeps the system idle most of the time and only fires the boiler when the property gets close to freezing. Typical cold system pressure sits around 1 to 1.5 bar, so it's worth checking the pressure gauge before you leave, since a system already low on pressure is more likely to lock out over winter, right when you need it working.
This approach avoids the labour of a full drain-down and means the property is ready to use as soon as you arrive. Its weak points are different: a power cut, a boiler fault, a thermostat left on the wrong setting, or simply nobody resetting a tripped system, and the frost protection stops working without anyone knowing until a pipe has already frozen and split. If a pipe does let go while the heating is meant to be protecting it, the signs can be subtle at first, which is why our guide to plumbing leak detection is worth knowing about before you need it, since it covers what non-invasive detection finds once heating pipework is suspected.
Side by side
| Factor | Drain down | Heating on (frost-protect) |
|---|---|---|
| Main risk | Incomplete drain leaves trapped water to freeze | Depends on power, boiler and thermostat staying reliable |
| Effort before leaving | Higher — needs a thorough, methodical drain | Lower — check settings and pressure, then leave |
| Ready to use on return | Needs refilling and bleeding before use | Usually ready immediately |
| Running cost while empty | None | Small, intermittent heating cost |
| Best suited to | Longer unoccupied periods, or an unreliable power supply | Shorter absences, or where periodic checks are arranged |
Neighbour and periodic checks
Whichever option you choose, the single biggest factor in how much damage a winter leak causes is how quickly it's noticed. A leak found within days is a repair. The same leak left for six weeks over a closed winter season is often a much larger job, and a much larger insurance claim.
A neighbour, local contact, or property manager who can look in periodically is worth more than either drain-down or heating strategy on its own. A short checklist for whoever's checking:
- Listen for running water when nothing should be drawing any, particularly near the stop tap or meter.
- Look for damp patches, staining, or a musty smell, especially near bathrooms, kitchens or where pipework runs through external walls.
- Check the boiler is still showing normal status, not locked out or displaying a fault code.
- Confirm the heating is actually firing on cold days, not just switched on, since a failed component can leave the display looking normal while nothing is happening.
If a check turns up a suspected leak with no obvious visible cause, non-invasive water leak detection can confirm and locate it without opening up walls, floors or ceilings, which matters even more in a property nobody is living in day to day.
Insurance and unoccupancy
Most buildings insurance policies include specific conditions for unoccupied properties, commonly requiring either the water system drained down, or the heating maintained above a minimum temperature, plus a limit on how many consecutive days the property can sit empty. These clauses vary between insurers and policies, so it's worth checking the exact wording for your second home rather than assuming the same rule applies everywhere.
If a leak does happen, water damage is usually covered as standard under buildings insurance, and the Association of British Insurers estimates escape of water costs insurers about £1.8 million in payouts every day nationally, which gives a sense of how common these claims are. Separately, price-comparison service Confused.com notes that trace and access cover pays to find the leak, access it, and make good the damage caused by the search itself, not the pipe repair, with policies commonly covering up to around £5,000 for that element. A written trace and access report from a professional visit supports that part of a claim.
Second homes across Cornwall & Devon
The mix of coastal cottages, converted barns and older granite and cob-built properties common across Cornwall and Devon second homes adds its own wrinkle to this decision. Thick granite or cob walls hold pipework differently to modern stud walls, sometimes routed through external masonry that gets colder faster than an internally-run pipe would. Cob in particular is a solid, dense wall construction with less cavity space, meaning pipes are often closer to the cold outer face than owners expect.
We see this most weeks in winter: a second home left on frost-protect through a run of mild South West weather, then caught out by one sharp cold snap that the system wasn't quite ready for, or a granite-walled cottage where a single external pipe run froze despite the rest of the house staying warm. Coastal exposure adds wind-chill on top of the air temperature, which can catch out a frost-protect setting calibrated to a more sheltered reading. None of this changes the fundamentals above, but it's worth factoring in when deciding which approach suits a particular property.
Frequently asked questions
Is it better to drain down a second home or leave the heating on over winter?
Both work if done properly. A full drain-down removes the water that could freeze, so there is nothing to burst, but it must be done thoroughly or trapped water in a low point still freezes. Leaving heating on a low frost-protect setting keeps pipes above freezing but depends on the boiler, power and thermostat all working while you're away.
What temperature should I leave the heating at for an empty second home?
Most modern boilers and thermostats have a frost-protection setting, often around 5 to 12 degrees, that keeps the system running only when temperatures drop close to freezing. Check your specific boiler's manual, since the exact frost-protect behaviour varies between manufacturers.
Can a drain-down still leave a pipe at risk of freezing?
Yes, if the drain-down is incomplete. Trapped water in a dipped section of pipe, an outside tap that wasn't isolated, or a cistern that wasn't fully emptied can still freeze and split even after the main system is drained. A methodical drain-down, checked at every low point, is what makes the difference.
Should I ask a neighbour to check on an empty second home in winter?
It's one of the most useful things an owner can arrange. A neighbour or local contact who can look in periodically, check for a running water sound, damp patches, or a stopped boiler, catches a problem in days rather than the weeks or months it might otherwise go unnoticed.
Does my insurance require the heating to stay on or the water drained?
Unoccupied property clauses vary by insurer and policy, often requiring either the water system drained down or the heating kept running above a minimum temperature during cold periods, alongside a maximum number of unoccupied days. Check your specific policy wording before deciding, since the standard approach differs between insurers.
What does escape of water cover if a pipe bursts while the property is empty?
Water damage is usually covered as standard in buildings insurance, and the Association of British Insurers estimates escape of water costs insurers about £1.8 million in payouts every day nationally. Separately, trace and access cover, commonly up to around £5,000, pays to find and reach the leak rather than repair the pipe itself.
How do I know if a second home has a hidden leak after being left empty?
A water bill that hasn't dropped despite the property being unoccupied, a stop tap that hums or a meter that keeps turning with everything off, and damp patches or a musty smell on return are the main signs. Non-invasive leak detection can confirm and locate a suspected leak without opening up walls or floors.
Come back to a damp patch or a bill that doesn't add up?
If your second home has come through winter with a suspected leak, we'll trace it across Cornwall & Devon with non-invasive equipment and document it for your insurer if needed.
Call Dickie on 07822 025 911 No Find, No Fee on residential leak detection (subject to terms)