You drive out on the first mild Saturday in weeks, put the key in the door, and the carpet in front of the kitchen cabinet is soaked through and cold. Nothing went wrong out there this week. The night that did this was ten days ago at 28 degrees, and by breakfast the next morning there was nothing at all to see.
Water expands as it freezes and a closed pipe has nowhere to put the extra volume, so the pipe splits. The timing is what catches people. That split happens while everything is still frozen solid, so nothing leaks, and a broken water system looks exactly like one that came through the cold fine. The leak starts on the thaw, often a day or two later and very often when nobody is there. It is why freeze damage is usually found as water damage, hours after the water started moving.
A sensor stops none of that. What it changes is when you find out: on the night rather than at the thaw, while the water is still liquid and somebody can shut the supply off, put a heater in, or drive over and drain it. A discovery becomes a decision, which is a real improvement and not remotely the same thing as prevention.
Monitoring is not winterising. If the rig is being stored through a real winter, blow the lines out and use antifreeze. A temperature alert is for the shoulder seasons and the unexpected cold snap, not a substitute for draining a system you are walking away from. Everything below assumes you have done that, or that the rig is in use and the water is in it for a reason.
Cold does not arrive everywhere at once
Interior air temperature is close to useless as a warning, because hardly any of your plumbing lives in the space the thermostat is measuring. You can be perfectly comfortable at head height while the pipes under the floor are below freezing.
Of the fixed parts the wet bay goes first: exposed to the road, usually uninsulated, and holding the pump, the filters and the low point drains. Underbelly runs are enclosed, which owners hear as heated. They are not, and a heated underbelly is only heated while it has power. Slides are worse than most people expect, with thin floors and plumbing exposed on three sides.
Ahead of all of it is the city water hose. A connected hose is a thin line of standing water lying in open air, and it freezes first, every time, and takes the inlet with it when it goes. If a hard night is coming and you do one thing, disconnect the hose.
Two sensors, three if you are thorough
The first goes in the wet bay, which crosses your threshold hours before the living area does and is the only reading that matches what the pipes are experiencing. The second goes inside at chest height, out of the sun, where it tells you whether the furnace is keeping up and gives the wet bay number something to sit against. Buying a third? Underbelly, or against the floor near the water lines.
Put the alert above freezing
An alert at 32 degrees fires as the problem starts, which only moves your worrying earlier. You want the warning while the water is still liquid, so set the number somewhere in the high thirties: high enough for a margin, low enough that it is not going off every clear evening in October. Then adjust it for the drive, because the threshold is really a measure of how long it takes to reach the rig. Tight is fine for a trailer on your own driveway. Two hours away, with a friend who has the key and work in the morning, you want considerably more.
The power fails first, the cold second
Almost every freeze that gets somebody is two failures in a row, and the freeze is the second one. The first is that the power went out: a breaker trips, the park loses supply, a cord gets knocked, and the furnace stops along with the tank heaters. The rig then takes hours to cool far enough for a temperature alert to fire, and they are wasted hours.
So alert on shore power too. You hear about the first failure as it happens rather than the second one much later, which is a message at eleven at night instead of four in the morning, and usually the difference between somebody fixing this with a walk to a pedestal and nobody fixing it at all.
Which sensor survives out there
Any supported sensor reads the living area happily. The wet bay is a harder posting: cheap sensors are specified for indoor use, and a wet bay in January is closer to outdoors than in, so a sealed enclosure such as the RuuviTag’s is worth the extra money there. Coin cells also lose capacity in the cold, so the sensor goes quiet in exactly the weather you fitted it for. Put a battery alert on anything outside the heated space. Our compatibility database says what we read from each device, including the ones we would not put in a wet bay.
Decide the phone call in advance
An alert is only worth having if it turns into somebody doing something, and two in the morning is a poor time to work out who. Sort it out in October:
- The campground office or the storage yard. Staff on site can reset a breaker or check a propane tank in minutes.
- A neighbour or a nearby friend with a key, told in advance that you might ring at an unsociable hour.
- Where your low point drains are, learned now rather than described down the phone to somebody on gravel with a torch.
- If it sits somewhere with nobody around, the alert is information for the drive and winterising is the actual protection. Checking on a stored rig is its own problem, mostly a connectivity one.
None of this takes long. A sensor in the wet bay, one inside, a threshold in the high thirties, an alert on the shore power, and somebody nearby who has agreed to be rung. Then a cold night is just a cold night, and the bad one reaches you while it is happening, rather than on the first mild Saturday in March with your hand on a wet carpet.
