A smart water leak detector is worth fitting in a second home, but the type matters. Sensor pucks only react to water that reaches them, so a leak under a floor or inside a wall goes unnoticed. Flow monitors and auto shut-off valves catch continuous flow, which is the signature of most hidden leaks, and can close the supply while you are away.
You lock up the house in Padstow or Fowey on a Sunday evening and do not come back for three weeks, or three months. In between, nobody hears the drip, nobody notices the meter turning and nobody smells the damp. That gap is exactly what a smart leak detector is meant to fill. The trouble is that the phrase covers three very different pieces of kit, and each one sees a leak in a different way. This guide explains what each type can and cannot do, what a hidden pipe leak looks like to it, and why a device on the wall is a good first line but never the last one.
Three kinds of device, three ways of seeing a leak
Before comparing them it helps to be clear about what a leak actually does. Water escapes from a pipe, joint or appliance. It either pools where it can be seen, soaks into something (a floor, a wall, the ground) or runs away to a drain. Only the first of those is obvious. The other two are what we spend most of our time finding with professional water leak detection, and they are the ones a second-home owner should worry about most.
Sensor pucks (spot detectors)
These are small battery discs with two metal contacts on the underside. Place one under the sink, behind the washing machine, beside the boiler or under the hot water cylinder. When water bridges the contacts, the puck sends an alert to your phone through a hub or Wi-Fi. They are cheap, quick to fit and useful where a leak will pool on a hard surface.
What they miss: anything that never reaches the puck. A weeping joint inside a stud wall, a pinhole in a pipe under a screed floor or a leaking underfloor heating loop can run for weeks without a drop touching the sensor. They also miss a leak that runs straight to a drain, such as a failed toilet fill valve or an overflow that discharges outside.
Flow monitors
A flow monitor clamps onto or is plumbed into the incoming main and watches how water moves through it. It learns the normal rhythm of the house and flags anything that does not fit: a low steady trickle at 3am, or a tap left running. Some clamp-on versions use ultrasound and need no plumbing work at all.
What they miss: a leak that is downstream of the monitor but too small to register, and anything on the heating circuit, which is a sealed system that the mains monitor never sees. A leak on the supply pipe between the boundary and the house is also outside its view if the device sits after the internal stopcock.
Automatic shut-off valves
The most useful type for an empty property. A motorised valve sits on the incoming main, usually with a flow monitor built in, and closes the supply when it detects continuous flow, a burst, or a signal from a linked sensor puck. Some let you close the valve from your phone when you leave. If a pipe splits during a cold snap, the house is shut off within minutes rather than flooding until the next visit.
What they miss: the same blind spots as a flow monitor, plus a practical one. Once the valve has closed, you still need someone to find out why and put it right before the water can go back on.
What a hidden pipe leak looks like to each device
Picture a small split in a copper pipe buried in the kitchen floor of a 1970s bungalow near St Austell. It leaks a litre or two an hour into the sand and cement screed beneath the tiles. Nothing shows on the surface for a fortnight.
| Device | What it sees | Outcome |
|---|---|---|
| Sensor puck under the sink | Nothing, the water never reaches it | No alert; damp shows weeks later |
| Flow monitor on the main | A steady trickle that never stops | Alert to your phone within a day or so |
| Auto shut-off valve | The same continuous flow | Supply closed; alert sent; house protected |
Now picture a heating pipe leaking under the same floor. Every device on the mains stays silent, because the heating circuit is filled once and then sealed. The only clue is the boiler pressure gauge creeping down, which is the same warning sign described in our guide to a boiler that keeps losing pressure. If the house has a filling loop left open, even that clue disappears.
The alert has gone off. Now what?
A phone notification at 2am while you are two hundred miles away is unsettling, so it helps to have a plan written down before it happens.
- Close the supply. If you have a smart valve, close it from the app. If not, ring whoever holds a key and ask them to turn the stopcock, then check nothing is visibly pouring.
- Read the meter. Ask your keyholder to photograph the meter with everything off. If the dial still creeps, the leak is between the meter and the stopcock, or the stopcock is not sealing. Our guide to a water meter that moves when nothing is on explains how to read that.
- Look at the obvious places. Under the sink, around the cylinder, at the boiler, behind the toilet. Many alerts are a simple failed washer or an overflowing tank.
- Do not let the house sit wet. If water has got into a floor or wall, open windows if it is safe, and get the heating on low. A cottage with cob or lime plaster holds moisture for a long time.
- Book a survey before the water goes back on. If the source is not obvious, leaving the supply on means the damage carries on growing.
Placing sensors so they actually help
Pucks earn their keep when they sit where water will collect. Some spots most owners forget:
- The airing cupboard floor, beneath the cylinder and any pressure relief pipework.
- Behind the washing machine and dishwasher, where hoses fail and puddles hide.
- Under the bath panel and beside the shower tray, where a failed seal drips onto the floor below.
- In the loft beside the cold water tank, if the house still has one.
- Next to the boiler, especially a combi in a cupboard, where a dripping condensate or pressure relief valve will pool.
Fit the pucks on the floor rather than on a shelf, and test each one with a wet finger after installing. Check the batteries twice a year, ideally when you change the smoke alarm batteries at the same time.
Why a device is not the whole answer
Every device described here is a messenger. It tells you that water is escaping, and in the best case it stops the flow. None of them can tell you where the pipe has failed, which is the question that matters once the panic subsides. Nor can any of them check the parts of a Cornish property that cause the most trouble: the long supply pipe from the lane to the house, the heating loops under a slate floor, or the pipework in a granite wall that was built a century before central heating existed.
Those are found with acoustic listening, thermal imaging and tracer gas, one method confirming the other, by someone on site who does leak detection across Cornwall every week. If your smart system has raised an alarm and the source is not obvious, an overnight meter test is the simplest way to confirm a real leak before you book anyone, and it can be done by your keyholder in ten minutes.
A practical set-up for an empty Cornish house
If you are starting from nothing, a sensible order is this. First, know where the stopcock is and make sure it turns freely, because everything else depends on it. Second, fit an automatic shut-off valve with flow monitoring on the incoming main, so a burst cannot run for weeks. Third, add sensor pucks at the five spots listed above for the leaks that pool rather than flow. Fourth, note your meter reading each time you leave and each time you arrive, and keep them in your phone. A rising gap between the two with the house empty is the earliest possible warning, and the numbers are exactly what an insurer will ask for later.
Fifth, and easy to skip: turn the water off at the stopcock when you leave for more than a few days, and in winter leave the heating on a frost setting. A device is a backstop. Prevention costs nothing.
Frequently asked questions
Will a smart leak detector find a leak under the floor?
A sensor puck will not, because it only reacts to water that touches it. A flow monitor or auto shut-off valve on the mains can spot the continuous flow such a leak causes, but it cannot say where the pipe has failed. Locating it still needs a survey on site.
Do I need Wi-Fi in the house for a leak detector to work?
Most app-based systems do, since alerts travel over your broadband. Some hubs take a SIM card as a backup, and a few shut-off valves will still close on their own without any connection at all. If the house has no internet, a self-acting valve is the safer choice.
Can a smart valve protect the central heating too?
No. The heating circuit is a sealed system filled from the mains once and then isolated, so a mains valve never sees a heating leak. The warning sign is the boiler pressure gauge dropping. Ask your keyholder to photograph the gauge on each visit.
Should I just turn the water off when I leave?
Yes, if the house will be empty for more than a few days and nothing needs the supply. Turning the stopcock off removes most of the risk in one go. Keep the heating on a low frost setting in winter, because a shut-off supply does not stop pipes freezing.
Will my insurer want a leak detector fitted?
Many policies have conditions about unoccupied periods, such as heating being left on or water being turned off. Some insurers offer discounts for shut-off devices. Read your own policy wording, because the conditions vary and a breach can affect a claim.
Alert gone off? We can find the cause
If your sensor or smart valve has flagged a problem in a Cornish second home and the source is not obvious, we can attend quickly, locate the leak without unnecessary damage and give you a report your insurer will accept.
