The supply line feeding your evaporative cooler runs through unconditioned space. Skip the fall shutdown and it's not the cooler that fails — it's the pipe.
Evaporative coolers are a genuinely good fit for our climate — they move a lot of air cheaply, and our humidity is low enough that they actually work. The catch is the water line. It's a small-diameter copper or plastic supply run to a unit sitting on the roof or the side of the house, and it spends the winter in exactly the conditions that split pipes.
Every year we get calls in March from people whose cooler line let go in January and quietly ran down the inside of a wall. The fall shutdown is a forty-five minute job that prevents it.
When to do it
Along the Front Range, aim for the first week of October. Our first hard freeze usually lands somewhere between late September and mid-October, and the forecast rarely gives you much notice. If you're reading this in November and haven't done it yet, do it today rather than waiting for a warm weekend — the damage happens on the first night below freezing, not gradually.
The shutdown, step by step
- Turn the cooler off at the switch, then shut off the breaker so nobody runs it by accident.
- Close the water valve feeding the cooler. It's usually in the basement, crawlspace or utility room where the line starts — not at the cooler itself.
- Open the bleed or drain fitting on the line and let it empty completely. Any water left in a horizontal run is what freezes and splits it.
- Disconnect the supply line at the cooler and leave it open so it can drain and stay dry.
- Drain the reservoir pan and clean out the sediment. Standing water plus a winter of freeze-thaw is what rusts pans through.
- Pull the pads if they're saturated or at the end of their life — a wet pad left in place all winter grows things you don't want blowing into the house in May.
- Cover the unit with a fitted cover, and cover the ceiling vent inside the house too. An uncovered swamp cooler is a chimney: it dumps your heated air out through the roof all winter.
The one people skip
Covering the inside vent. It feels optional, but an open cooler vent can account for a noticeable chunk of a winter heating bill — you are effectively leaving a window open in the ceiling for five months.
If you're on a roof-mounted unit, think about the ladder
Most swamp coolers around here are roof-mounted, which means the whole job happens on a pitched roof, in October, often on frost. There is no shame in having someone else do this. It's a small service call, we're already on the roof for the spring start-up anyway, and the number of ladder injuries we hear about every autumn is not small.
What spring start-up should include
Winterizing is only half the cycle. When you bring the cooler back in April or May, it's worth doing more than just turning the water back on:
- New pads. They're consumable — mineral-caked pads cut airflow and cooling capacity dramatically.
- Check the pump and float valve. Both are cheap and both fail quietly, and you find out on the first 95-degree day.
- Check the belt tension and lubricate the motor bearings if it's a belt-drive unit.
- Pressurize the line and watch the fittings for a few minutes before you walk away.
We do both ends of the season, and if you'd rather not think about it at all, the Rock Solid Club maintenance plan for swamp coolers covers the shutdown and the start-up so it just gets handled.
